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BEGIN:VEVENT
UID:calendar:2343:field_when:0:0
SUMMARY:Partitioning pairs of sigma-scattered linear orders (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2343
LOCATION:Building 604\, Room 103
DESCRIPTION:Speaker: Thilo Weinert (BGU)\n
\n
Abstract:\n
This is part 2 of last week's talk [1].\n
\n
\n
[1] http://math.biu.ac.il/node/2333
END:VEVENT
BEGIN:VEVENT
UID:calendar:2342:field_when:0:1
SUMMARY:Modular Galois representations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170510T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170510T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2342
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Devika Sharma (Weizmann Institute of Science)\n
\n
Abstract:\n
See attached.\n
\n
http://math.biu.ac.il/files/math/seminars/abstract_bar_ilan.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2341:field_when:0:2
SUMMARY:The Mackey bijection via algebraic families of Harish-Chandra modules
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170517T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170517T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2341
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Eyal Subag (Pennsylvania State University)\n
\n
Abstract:\n
>In 1975 George Mackey pointed out an analogy between certain unitary \n
>representations of a semisimple Lie group and its Cartan Motion group. \n
>Recently this analogy was proven to be a part of a bijection between the \n
>tempered dual of a real reductive group and the tempered dual of its Cartan \n
>Motion group. \n
>In this talk I will show\, in the case of SL(2\,R)\, how algebraic families of \n
>Harish-Chandra modules can be used to characterize the Mackey bijection and \n
>extend it to an algebraic isomorphism between the admissible duals.\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2340:field_when:0:3
SUMMARY:Stability in representation theory of the symmetric groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170503T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170503T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2340
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Inna Entova-Aizenbud (Ben-Gurion University)\n
\n
Abstract:\n
In the finite-dimensional representation theory of the symmetric groups\n
$$S_n$$ over the base field $$\mathbb{C}$$\, there is an an interesting\n
phenomena of "stabilization" as $$n \to \infty$$: some representations\n
of $$S_n$$ appear in sequences $$(V_n)_{n \geq 0}$$\, where each $$V_n$$\n
is a finite-dimensional representation of $$S_n$$\, where $$V_n$$ become\n
"the same" in a certain sense for $$n >> 0$$.\n
One manifestation of this phenomena are sequences $$(V_n)_{n \geq 0}$$\n
such that the characters of $$S_n$$ on $$V_n$$ are "polynomial in $n$".\n
More precisely\, these sequences satisfy the condition: for $$n>>0$$\, the\n
trace (character) of the automorphism $$\sigma \in S_n$$ of $$V_n$$ is\n
given by a polynomial in the variables $$x_i$$\, where $$x_i(\sigma)$$ is\n
the number of cycles of length $$i$$ in the permutation $$\sigma$$.\n
In particular\, such sequences $$(V_n)_{n \geq 0}$$ satisfy the agreeable\n
property that $$\dim(V_n)$$ is polynomial in $$n$$.\n
Such "polynomial sequences" are encountered in many contexts:\n
cohomologies of configuration spaces of $$n$$ distinct ordered points on\n
a connected oriented manifold\, spaces of polynomials on rank varieties\n
of $$n \times n$$ matrices\, and more. These sequences are called\n
$$FI$$-modules\, and have been studied extensively by Church\, Ellenberg\,\n
Farb and others\, yielding many interesting results on polynomiality in\n
$$n$$ of dimensions of these spaces.\n
A stronger version of the stability phenomena is described by the\n
following two settings:\n
\n
\n
- The algebraic representations of the infinite symmetric group\n
$$S_{\infty} = \igcup_{n} S_n\,$$ where each representation of\n
$$S_{\infty}$$ corresponds to a ``polynomial sequence'' $$(V_n)_{n \geq\n
0}$$.\n
\n
- The "polynomial" family of Deligne categories $$Rep(S_t)\, ~t \in\n
\mathbb{C}$$\, where the objects of the category $$Rep(S_t)$$ can be\n
thought of as "continuations of sequences $$(V_n)_{n \geq 0}$$" to\n
complex values of $$t=n$$. \n
\n
I will describe both settings\, show that they are connected\, and\n
explain some applications in the representation theory of the symmetric\n
groups.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2339:field_when:0:4
SUMMARY:Triple Massey products
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170426T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170426T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2339
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Eli Matzri (Bar-Ilan University)\n
\n
Abstract:\n
Fix an arbitrary prime p. Let F be a field containing a primitive p-th root \n
of unity\, with absolute Galois group G_F\, and let H^n denote its mod p \n
cohomology group\, H^n(G_F\,\Z/p\Z).\n
The triple Massey product (abbreviated 3MP) of weight (n\,k\,m) \in N^3\, is a \n
partially defined\, multi-valued function \n
< \, \, >: H^n x H^k x H^m \to H^{n+k+m-1}.\n
\n
The recently proved 3MP conjecture states that every defined 3MP of weight \n
(1\,1\,1) contains the zero element.\n
In this talk I will present the idea of a new proof of the 3MP conjecture for \n
odd primes\, inspired by the idea of linearization. The nice thing is that it \n
actually works for 3MP of weight (1\,n\,1) for arbitrary n.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2338:field_when:0:5
SUMMARY:Diagonal flows\, joinings and arithmetic
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170430T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170430T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2338
LOCATION:Colloquium Room
DESCRIPTION:Speaker: Elon Lindenstrauss\n
\n
Abstract: Arithmetic quotients of algebraic groups such as the space of unit \n
volume lattices in R^n can be studied fruitfully from many directions and \n
contain deep and subtle arithmetic information. Homogeneous dynamics studies \n
these spaces by considering the action of a subgroup of the algebraic group \n
on such a quotient. Of particular interest is the action of multiparameter \n
diagonal groups: these display remarkable rigidity properties that are absent \n
in the context of one parameter diagonalizable group actions. One aspect \n
of this rigidity is joining rigidity: under suitable conditions\, this \n
rigidity implies that knowing that an orbit of a multiparameter \n
diagonalizable group in a product of two arithmetic quotients is \n
equidistributed in each one of these quotients individually implies joint \n
equidistribution. I would explain this phenomena as well as some \n
arithmetic consequences.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2337:field_when:0:6
SUMMARY:Differential equations and algebraic points on transcendental varieties
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170423T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170423T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2337
LOCATION:Colloquium Room
DESCRIPTION:Speaker: Gal Binyamini\n
\n
Abstract: The problem of bounding the number of rational or algebraic points \n
of a given height in a transcendental set has a long history. In 2006 Pila \n
and Wilkie made fundamental progress in this area by establishing a \n
sub-polynomial asymptotic estimate for a very wide class of transcendental \n
sets. This result plays a key role in Pila-Zannier's proof of the \n
Manin-Mumford conjecture\, Pila's proof of the Andre-Oort conjecture for \n
modular curves\, Masser-Zannier's work on torsion anomalous points in elliptic \n
families\, and many more recent developments. I will briefly sketch the \n
Pila-Wilkie theorem and the way it enters into the arithmetic applications. I \n
will then discuss recent work on an effective form of the Pila-Wilkie theorem \n
(for certain sets) which leads to effective versions of many of the \n
applications. I will also discuss a joint work with Dmitry Novikov on \n
sharpening the asymptotic from sub-polynomial to poly-logarithmic for certain \n
structures\, leading to a proof of the restricted Wilkie conjecture. The \n
structure of the systems of differential equations satisfied by various \n
transcendental functions plays a key role for both of these directions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2335:field_when:0:7
SUMMARY:Azumaya algebras of period 2 with involution
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170419T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170419T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2335
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Uriya First (University of British Columbia)\n
\n
Abstract:\n
Albert showed that a central simple algebra A over a field F admits an \n
involution of the first kind\, i.e. an F-antiautomorphism of order 2\, if and \n
only if the order of the Brauer class of A in the Brauer group of F divides \n
2.\n
\n
Azumaya algebras are generalizations of central simple algebras\, defined over \n
an arbitrary commutative base ring (or scheme)\, and can be used to define the \n
Brauer group of a commutative ring. They play an important role in the study \n
of classical groups over schemes.\n
\n
Albert's theorem fails in the more general setting where A is an Azumaya \n
algebra over a commutative ring R. However\, Saltman showed that in this case \n
there is an Azumaya algebra B that is Brauer equivalent to A and admits an \n
involution of the first kind. Knus\, Parimala and Srinivas later showed that \n
one can in fact choose B such that deg(B) = 2*deg(A).\n
\n
I will discuss a joint work with Ben Williams and Asher Auel where we use \n
topological obstructions to show that deg(B) = 2*deg(A) is optimal when \n
deg(A)=4. More precisely\, we construct a regular commutative ring R and an \n
Azumaya R-algebra A of degree 4 and period 2 such that the degree of any \n
Brauer equivalent algebra B admitting an involution of the first kind divides \n
8.\n
\n
If time permits\, I will also discuss examples of Azumaya algebras admitting \n
only symplectic involutions and no orthogonal involutions. This stands in \n
contrast to the situation in central simple algebras where the existence of a \n
symplectic involution implies the existence of an orthogonal involution\, and \n
vice versa if the degree is even.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2333:field_when:0:8
SUMMARY:Partitioning pairs of sigma-scattered linear orders
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170420T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170420T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2333
LOCATION:Building 604\, Room 103
DESCRIPTION:Speaker: Thilo Weinert (BGU)\n
\n
Abstract:\n
We are going to continue the analysis of generalised scattered orders\, \n
proving the result described towards the end of Chris Lambie-Hanson’s talk. \n
This states that consistently\, for every sigma-scattered linear ordering \n
there is a colouring of its pairs in black & white such that every triple \n
contains a white pair and every copy of one of the following order-types \n
contains a black pair:\n
\n
* omega_1^omega\n
* (omega_1^omega)^*\n
* omega_1 * (omega * omega^*)^omega\n
* omega_1^* * (omega * omega^*)^omega\n
* (omega * omega^*)^omega * omega_1\n
* (omega * omega^*)^omega * omega_1^*\n
\n
This generalises a 46-year-old Theorem of Erdős & Rado about ordinals. A \n
sufficient hypothesis implying this theorem is the existence of a colouring \n
of the pairs of omega_1 * omega in black & white such that every triple \n
contains a black pair and every subset of full order-type contains a white \n
one. Time permitting we may present a proof that stick = b = Aleph_1 implies \n
the existence of such a colouring. Here b is the unbounding number and stick \n
= Aleph_1 is a weakening of the club principle which was considered by \n
Baumgartner 41 years ago\, named by Broverman\, Ginsburg\, Kunen & Tall two \n
years thereafter and twenty years ago reconsidered as a cardinal \n
characteristic by Fuchino\, Shelah & Soukup.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2331:field_when:0:9
SUMMARY:Free subalgebras of graded algebras\, infinite words\, and Golod-Shafarevich \n
algeras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170405T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170405T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2331
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Be'eri Greenfeld (Bar-Ilan University)\n
\n
Abstract:\n
The famous Koethe conjecture asserts that the sum of two nil left ideals is \n
always nil. This still open problem\, which is sometimes considered the \n
central open problem in ring theory\, has attracted many researchers and \n
inspired a flurry of results toward a better understanding of its validity.\n
\n
\n
\n
Its most popular equivalent formulation nowadays is\, that the polynomial ring \n
R[x] over a nil ring R is equal to its own Jacobson radical.\n
\n
The observation that R[x] is naturally graded\, and every homogeneous element \n
is nilpotent (i.e. R[x] is "graded nil") motivated L. Small and E. Zelmanov \n
to ask ('06) whether a graded nil algebra is always Jaocbson radical.\n
\n
This was disproved by A. Smoktunowicz a few years ago\, and should be \n
mentioned together with another result by Smoktunowicz\, disproving a \n
conjecture of L. Makar-Limanov: she proved that there exists a nil ring R \n
such that after tensoring with central variables (specifically: \n
R[x_1\,...\,x_6]) it contains a free subalgebra. Such ring can exist only over \n
countable base fields.\n
\n
\n
\n
In this talk we present a new construction\, which provides a monomial\, graded \n
nilpotent ring (a stronger property than graded nil) which contains a free \n
subalgebra. Our methods involve combinatorics of infinite words\, and gluing \n
together sequences of letters which arise from appropriate morphisms of free \n
monoids. In particular\, this resolves Small-Zelmanov's question and can be \n
thought of as a continuation of Smoktunowicz's counterexample to \n
Makar-Limanov's conjecture (as in our construction the base field can be \n
arbitrary).\n
\n
\n
\n
We also construct finitely generated graded Golod-Shafarevich algebras in \n
which all homogeneous elements are nilpotent of bounded index\, and prove that \n
such phenomenon cannot appear in monomial algebras. This example also \n
indicates the lack of a graded version for the Shirshov height theorem.\n
\n
\n
\n
The talk is based on joint work with Jason P. Bell.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2330:field_when:0:10
SUMMARY:הסימן א"ת ב"ש וסימנים נוספים לקביעת מועדים
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170131T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170131T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2330
LOCATION:חדר מחלקה
DESCRIPTION:Speaker: ד"ר שי ואלטר\, מכללה ירושלים ומכללת \n
אחוה.\n
\n
Abstract:\n
בלוח העברי הנוכחי מצויים כללים קבועים \n
לסידור לוח השנה.\n
\n
כללים אלו יוצרים סדר קבוע של חלק גדול \n
מחודשי השנה\, והופכים את סידור לוח השנה \n
למלאכה קלה יחסית.\n
\n
להקלת חישוב הלוח נוצרו מספר סימנים \n
מנמוניים המופיעים בספרי המעברים.\n
\n
חלק מסימנים אלו הם סימנים לקביעת המועדים\, \n
ואחד המפורסמים שבהם הוא הסימן א"ת ב"ש ...\n
\n
בהרצאה נדון בתולדותיו של סימן זה\, במופעיו \n
השונים ובמשמעויות שניתנו לסימן זה בשנים \n
האחרונות.\n
\n
ברקע נזכיר גם סימנים נוספים לקביעת \n
המועדים\, ונדון אף בהם.\n
\n
*להרצאה המצולמת [1]*\n
\n
*למצגת ההרצאה [2]*\n
\n
\n
[1] https://www.youtube.com/watch?v=BoD9ogp3x08&\;feature=youtu.be\n
[2] http://u.math.biu.ac.il/~esheds/valter.pptx
END:VEVENT
BEGIN:VEVENT
UID:calendar:2328:field_when:0:11
SUMMARY:Symbolic dynamics for chaotic maps
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170402T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170402T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2328
LOCATION:Colloquium room\, Mathematics Dept. (building 216)
DESCRIPTION:Speaker: Prof. Omri Sarig\, Weizmann Institute of Science\n
\n
Abstract:\n
"Symbolic dynamics" is a powerful technique for describing the \n
combinatorial structure of large collections of orbits of dynamical systems \n
with "chaotic" behaviour. I will describe this technique\, and will report on \n
recent advances on the question what sort of "chaos" is needed to this method \n
to succeed. The talk is meant for a general audience\, including people with \n
little or no background in dynamical systems.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2324:field_when:0:12
SUMMARY:Partition relations and generalized scattered orders
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170330T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170330T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2324
LOCATION:Building 604\, Room 103
DESCRIPTION:Speaker: Chris Lambie-Hanson (BIU)\n
\n
Abstract:\n
The class of scattered linear orders\, isolated by Hausdorff\, plays a \n
prominent role in the study of general linear orders. In 2006\, Dzamonja and \n
Thompson introduced classes of orders generalizing the class of scattered \n
orders. For a regular cardinal kappa\, they defined the classes of \n
kappa-scattered and weakly kappa-scattered linear orders. For kappa = omega\, \n
these two classes coincide and are equal to the classical class of scattered \n
orders. For larger values of kappa\, though\, the two classes are provably \n
different. In this talk\, we will investigate properties of these generalized \n
scattered orders with respect to partition relations\, in particular the \n
extent to which the classes of kappa-scattered or weakly kappa-scattered \n
linear orders of size kappa are closed under partition relations of the form \n
tau -> (phi\, n) for n < omega. We will show that\, assuming kappa^{
END:VEVENT
BEGIN:VEVENT
UID:calendar:2322:field_when:0:13
SUMMARY:Cyclic descents\, toric Schur functions and Gromov-Witten invariants
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170326T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170326T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2322
LOCATION:Colloquium Room
DESCRIPTION:Speaker: Prof. Ron Adin \n
\n
Abstract:\n
Descents of permutations have been studied for more than a century. This \n
concept was vastly generalized\, in particular to standard Young tableaux \n
(SYT). More recently\, cyclic descents of permutations were introduced by \n
Cellini and further studied by Dilks\, Petersen and Stembridge. Looking for a \n
corresponding concept for SYT\, Rhoades found a very elegant solution for \n
rectangular shapes. In an attempt to extend the concept of cyclic descents\, \n
explicit combinatorial definitions for two-row and certain other shapes have \n
been found\, implying the Schur-positivity of various quasi-symmetric \n
functions. In all cases\, the cyclic descent set admits a cyclic group action \n
and restricts to the usual descent set when the letter /n/ is ignored. \n
Consequently\,\n
\n
the existence of a cyclic descent set with these properties was conjectured \n
for all shapes\, even the skew ones. This talk will report on the surprising \n
resolution of this conjecture: Cyclic descent sets exist for nearly all skew \n
shapes\, with an interesting small set of exceptions. The proof applies \n
non-negativity properties of Postnikov's toric Schur polynomials and a new \n
combinatorial interpretation of certain Gromov-Witten invariants. We shall \n
also comment on issues of uniqueness. Based on joint works with Sergi \n
Elizalde\, Vic Reiner\, Yuval Roichman.\n
\n
\n
\n
*Dr. Menachem Shlossberg invites you to a “haramat kosit” in celebration \n
of obtaining a postdoctorate *\n
\n
*at the University of Udine\, Italy\, at 1:30 PM next to the Colloquium Room*\n
\n
*ד"ר מנחם שלוסברג מזמין אתכם להרמת כוסית \n
לרגל קבלת משרת פוסט דוקטורט באונ' אודין \n
באיטליה*\n
\n
* בשעה 13:30 בחדר ע"י חדר המחלקה*\n
\n
\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2321:field_when:0:14
SUMMARY:The non-Euclidean lattice points counting problem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170327T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170327T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2321
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Amos Nevo\, Technion\n
\n
Abstract:\n
Euclidean lattice points counting problems\, the primordial example of which \n
is the Gauss circle problem\, are an important topic in classical analysis. \n
Their non-Euclidean analogs in irreducible symmetric spaces (such as \n
hyperbolic spaces and the space of positive-definite symmetric matrices) are \n
equally significant\, and we will present an approach to establishing such \n
results in considerable generality. Our method is based on dynamical \n
arguments together with representation theory and non-commutative harmonic \n
analysis\, and produces the current best error estimate in the higher rank \n
case. We will describe some of the remarkably diverse applications of \n
lattice point counting problems\, as time permits.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2319:field_when:0:15
SUMMARY:Milnor-Witt K-groups of local rings
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170322T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170322T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2319
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Stefan Gille (University of Alberta)\n
\n
Abstract:\n
Milnor-Witt K-groups of fields were discovered by Morel and Hopkins within \n
the framework of A^1 homotopy theory. These groups play a role in the \n
classification of vector bundles over smooth schemes via Euler classes and \n
oriented Chow groups. Together with Stephen Scully and Changlong Zhong we \n
have generalized these groups to (semi-)local rings and shown that they have \n
the same relation to quadratic forms and Milnor K-groups as in the field \n
case. An application of this result is that the unramified Milnor-Witt \n
K-groups are a birational invariant of smooth proper schemes over a field. \n
This is joint work with Stephen Scully and Changlong Zhong.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2318:field_when:0:16
SUMMARY:Sloshing\, Steklov and corners
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170319T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170319T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2318
LOCATION:Colloquium room\, Mathematics Dept. (building 216)
DESCRIPTION:Speaker: Iosif Polterovich\, University of Montreal\n
\n
Abstract:\n
The sloshing problem is a Steklov type eigenvalue problem describing small \n
oscillations of an ideal fluid. We will give an overview of some latest \n
advances in the study of Steklov and sloshing spectral asymptotics\, \n
highlighting the effects arising from corners\, which appear naturally in the \n
context of sloshing. In particular\, we will outline an approach towards \n
proving the conjectures posed by Fox and Kuttler back in 1983 on the \n
asymptotics of sloshing frequencies in two dimensions. The talk is based on a \n
joint work in progress with M. Levitin\, L. Parnovski and D. Sher.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2317:field_when:0:17
SUMMARY:Asymptotic Relations for Sharp Constants of Approximation Theory
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170320T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170320T154000
URL;VALUE=URI:http://math.biu.ac.il/node/2317
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Michael I. Ganzburg\, Hampton University\, Virginia\, USA\n
\n
Abstract:\n
In this talk we discuss asymptotic relations between sharp constants of \n
approximation theory\n
in a general setting. We first present a general model that includes a circle \n
of problems of\n
finding sharp or asymptotically sharp constants in some areas of univariate \n
and multivariate\n
approximation theory\, such as inequalities for approximating elements\, \n
approximation of individual\n
elements\, and approximation on classes of elements. Next we discuss \n
sufficient conditions that\n
imply limit inequalities and equalities between various sharp constants. \n
Finally\, we present\n
applications of these results to sharp constants in Bernstein-V. A. Markov \n
type inequalities of\n
different metrics for univariate and multivariate trigonometric and algebraic \n
polynomials and\n
entire functions of exponential type.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2307:field_when:0:18
SUMMARY:הלוח העברי: זמני המולדות ומשוואת הזמן \n
מהיבט אסטרונומי
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161213T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170207T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2307
LOCATION:חדר מחלקה
DESCRIPTION:Speaker: דוד גילאי\n
\n
Abstract:\n
* "עשה ירח למועדים שמש ידע מבואו" – המדרש\n
במסכת ראש השנה ותיסכולו של ר' חייא.\n
* הפרש הזמן בין מולד למולד אינו קבוע והוא\n
משתנה בתחום של עד ±7 שעות מהממוצע של 29.53\n
ימים. שעת המולד "מטיילת" על פני כל שעות\n
היממה באופן בלתי סדיר ויכולה לחול בכל\n
שעה שהיא (דוגמא מלוח טיקוצ'ינסקי). לר'\n
חייא לא היו כלים לחיזוי מדויק של מולד\n
הלבנה.\n
* מבחינה אסטרונומית קשה עד בלתי אפשרי\n
למצוא מחזוריות מושלמת במופעי המולדות.\n
* מאז ביטול הסנהדרין נקבע לוח המועדים בדרך\n
חישובית אך הזמן המדויק של תחולת המולד\n
כבר אינו משמעי לחישובים אלה.\n
* מאידך יש חשיבות לידיעה מדויקת של זמני\n
הזריחה והשקיעה בכל יום ולצורך כך יש\n
להכיר את מושג "משוואת הזמן".\n
* מטרת ההרצאה היא להבהיר את המקור לאי\n
סדירות המולדות ואת נושא משוואת הזמן\n
מההיבט האסטרונומי. במסגרת זו נדון\n
בנושאים הבאים:\n
* מישור המילקֶה (המישור האקליפטי) והטיית\n
ציר הסיבוב של כדור הארץ יחסית למישור זה\n
* ימי השיוויון וימי ההיפוך\n
* מישור תנועת הירח סביב כדור הארץ\n
ומיצובו יחסית למישור האקליפטי\n
* הגדרת המולד מבחינת גרמי השמים\n
* מאפייני מסלולי הכוכבים על פי חוקי קפלר.\n
אקסצנטריות מסלול.\n
* חוק הגרביטציה ומיקום כדור הארץ במישור\n
האקליפטי. הגדרת הפריגיאה והאפוגיאה\n
* הגורמים לחוסר הסדירות של זמני תחולת\n
המולד הם אקסצנטריות מסלולי הארץ והירח\n
שגורמים לשינויים במהירותם במהלך הקפת\n
הכוכב שהם סובבים \n
* הגורמים לשינויים באורך היממה הם\n
אקסצנטריות מסלול כדור הארץ והטיית ציר\n
הסיבוב שלו יחסית למילקה. שני גורמים אלה\n
יוצרים את "משוואת הזמן".\n
\n
* סיכום: למרות\, ואולי עקב\, אי הסדירות של\n
מופעי המולד הרכיבו חכמים לוח ארוך טווח\n
עם כללים ברורים לקביעת ראשי החודשים. לוח\n
זה מקיים את כל דרישות ההלכה ביחס לתחולת\n
הפסח באביב והימים בהם יחולו החגים\, אך הוא\n
סוטה מדי פעם מימי המולד האמיתיים. מאידך\n
משוואת הזמן מאפשרת לחזות בדיקנות את זמני\n
הזריחה והשקיעה בכל יום על אף השינויים\n
היומיים באורך היממה\, ולשמור על זמני\n
התפילות\, הנחת תפילין\, וכניסת ליציאת\n
שבתות וחגים.\n
\n
\n
\n
*ההרצאה המצולמת* [1] \n
\n
*מצגת ההרצאה* [2]\n
\n
\n
[1] https://www.youtube.com/watch?v=bI-neoJ1wuA\n
[2] http://u.math.biu.ac.il/~esheds/galai.ppsx
END:VEVENT
BEGIN:VEVENT
UID:calendar:2305:field_when:0:19
SUMMARY:Equilateral triangles in subsets of ${\mathbb R}^d$ of large Hausdorff \n
dimension
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170213T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170213T160000
URL;VALUE=URI:http://math.biu.ac.il/node/2305
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Bochen Liu\, University of Rochester\, NY\, USA\n
\n
Abstract:\n
I will discuss how large the Hausdorff dimension of a set $E\subset{\mathbb \n
R}^d$ needs to be \n
to ensure that it contains vertices of an equilateral triangle. An argument \n
due to Chan\, Laba \n
and Pramanik (2013) implies that a Salem set of large Hausdorff dimension \n
contains equilateral \n
triangles. We prove that\, without assuming the set is Salem\, this result \n
still holds in dimensions \n
four and higher. In ${\mathbb R}^2$\, there exists a set of Hausdorff \n
dimension $2$ containing no \n
equilateral triangle (Maga\, 2010).\n
I will also introduce some interesting parallels between the triangle problem \n
in Euclidean space \n
and its counter-part in vector spaces over finite fields. It is a joint work \n
with Alex Iosevich.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2303:field_when:0:20
SUMMARY:Weak fibration categories - theory and applications.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170205T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170205T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2303
LOCATION:seminar room
DESCRIPTION:Speaker: Ilan Barnea\n
\n
Abstract:\n
Model categories\, introduced by Quillen\, provide a very general context in \n
which it is possible to set up the basic machinery of homotopy theory. In \n
particalar they enable to define derived functors\, homotopy limits and \n
colimits\, cohomology theories and spectral sequences to catculate them. \n
However\, the structure of a model category is usually hard to verify\, and in \n
some interesating cases even impossible to define. In this lecture I will \n
define a much simpler notion then a model category\, called a weak fibration \n
category. By a theorem due to T. Schlank and myself\, a weak fibration \n
category gives rise in a natural way to a model category structure on its pro \n
category\, provided some technical assumptions are satisfied. This result can \n
be used to construct new model structures in different mathematical fields\, \n
and thus to import the methods of homotopy theory to these \n
situations. Examples will be given from the categories of simplicial \n
presheaves\, C*-algebras and complexes in Abelian categories. Applications \n
will be discussed with each example.\n
\n
The above encompasses joint work with Tomer M. Schlank\, Yonatan Harpaz\, \n
Geoffroy Horel\, Michael Joachim Snigdhayan Mahanta and Matan Prezma.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2301:field_when:0:21
SUMMARY:Characterizing sigma-scattered linear orders (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170126T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170126T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2301
LOCATION:seminar room
DESCRIPTION:Speaker: William Chen (BGU)\n
\n
Abstract:\n
This is an expository presentation following the paper "Minimality of non \n
$\sigma$-scattered orders" by Ishiu and Moore. In the first part of the talk \n
we will introduce the invariant $\Omega(L)$ of a linear order $L$\, and \n
characterize $\sigma$-scattered linear orders in terms of this invariant. In \n
the second part\, we will prove under the forcing axiom $\mathsf{PFA}^+$ that \n
any linear order which is minimal with respect to embedding among the non \n
$\sigma$-scattered orders must be either a real or Aronszajn type.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2300:field_when:0:22
SUMMARY:לוח השנה הבבלי
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161122T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161122T180000
URL;VALUE=URI:http://math.biu.ac.il/node/2300
LOCATION:חדר מחלקה
DESCRIPTION:Speaker: פרופ' נחום דרשוביץ\, אוניברסיטת תל \n
אביב\n
\n
Abstract:\n
בהרצאה נסקור כמה מקורות קדומים ללוחות \n
בבליים\n
\n
*מצגת ההרצאה [1]*\n
\n
*ההרצאה המצולמת [2]*\n
\n
\n
[1] http://u.math.biu.ac.il/~esheds/Babel.pdf\n
[2] https://www.youtube.com/watch?v=NAVqI2jwK3k&\;list=PLXF_IJaFk-9DWxOnG84eMXOxwxhpQY6D-&\;index=12
END:VEVENT
BEGIN:VEVENT
UID:calendar:2298:field_when:0:23
SUMMARY:Finite Groebner basis algebras with unsolvable nilpotency and zero divisor \n
problems
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170125T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170125T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2298
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Sergey Malev (Bar-Ilan University)\n
\n
Abstract:\n
Constructions of two algebras\, both with the ideal of relations defined by a \n
finite Groebner basis\, will be presented. For the first algebra the question \n
of whether a given element is nilpotent is algorithmically unsolvable\, for \n
the second the question of whether a given element is a zero divisor is \n
algorithmically unsolvable. This gives a negative answer to questions raised \n
by Latyshev.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2297:field_when:0:24
SUMMARY:Tame dynamical systems
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170123T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170123T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2297
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Michael Megrelishvili\, Bar-Ilan University\n
\n
Abstract:\n
Tame dynamical systems were introduced by A. K\"{o}hler in 1995 and their \n
theory was \n
developed during last decade in a series of works by several authors. \n
Connections to \n
other areas of mathematics like: Banach spaces\, model theory\, tilings\, cut \n
and project \n
schemes were established. A metric dynamical $G$-system $X$ is tame if every \n
element \n
$p \in E(X)$ of the enveloping semigroup $E(X)$ is a limit of a sequence of \n
elements \n
from $G$. In a recent joint work with Eli Glasner we study the following \n
general question:\n
which finite coloring $G \to \{0\, \dots \,d\}$ of a discrete countable group \n
$G$ defines a \n
tame minimal symbolic system $X \subset \{0\, \dots \,d\}^G$. Any Sturmian \n
bisequence \n
$\Z \to \{0\,1\}$ on the integers is an important prototype.\n
As closely related directions we study cutting coding functions coming from \n
circularly ordered \n
systems. As well as generalized Helly's sequential compactness type theorems \n
about families \n
with bounded total variation. We show that circularly ordered dynamical \n
systems are tame and \n
that several Sturmian like symbolic $G$-systems are circularly ordered.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2296:field_when:0:25
SUMMARY:Applications of measure rigidity to recurrence
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170122T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170122T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2296
LOCATION:seminar room
DESCRIPTION:Speaker: Alexander Fish\, School of Mathematics and Statistics\, University of \n
Sydney\, Australia\n
\n
Abstract:\n
\n
\n
We present a new approach (joint with M. Bjorklund (Chalmers)) for finding \n
new patterns in difference sets E-E\, where E has a positive density in Z^d\, \n
through measure rigidity of associated action. \n
\n
By use of measure rigidity results of Bourgain-Furman-Lindenstrauss-Mozes and \n
Benoist-Quint for algebraic actions on homogeneous spaces\, we prove that for \n
every set E of positive density inside traceless square matrices with integer \n
values\, there exists positive k such that the set of characteristic \n
polynomials of matrices in E - E contains ALL characteristic polynomials of \n
traceless matrices divisible by k.\n
\n
By use of this approach Bjorklund and Bulinski (Sydney)\, recently showed that \n
for any quadratic form Q in d variables (d >=3) of a mixed signature\, and any \n
set E in Z^d of positive density the set Q(E-E) contains kZ for some positive \n
k. Another corollary of our approach is the following result due to \n
Bjorklund-Bulinski-Fish: the discriminants D = {xy-z^2 \, x\,y\,z in B} over a \n
Bohr-zero non-periodic set B covers all the integers.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2294:field_when:0:26
SUMMARY:Characterizing sigma-scattered linear orders
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170119T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170119T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2294
LOCATION:seminar room
DESCRIPTION:Speaker: William Chen (BGU)\n
\n
Abstract:\n
This is an expository presentation following the paper "Minimality of non \n
$\sigma$-scattered orders" by Ishiu and Moore. In the first part of the talk \n
we will introduce the invariant $\Omega(L)$ of a linear order $L$\, and \n
characterize $\sigma$-scattered linear orders in terms of this invariant. In \n
the second part\, we will prove under the forcing axiom $\mathsf{PFA}^+$ that \n
any linear order which is minimal with respect to embedding among the non \n
$\sigma$-scattered orders must be either a real or Aronszajn type.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2292:field_when:0:27
SUMMARY:Linkage of quadratic Pfister forms
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170118T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170118T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2292
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Shira Gilat (Bar-Ilan University)\n
\n
Abstract:\n
Quadratic Pfister forms are a special class of quadratic forms that arise \n
naturally as norm forms of composition algebras. The Witt group I_q F of \n
quadratic forms (modulo hyperbolic forms) over a field F is a module over the \n
Witt ring of bilinear forms. This gives a most important filtration { I_q^n \n
F }. The n-fold Pfister forms\, which are tensor products of n Pfister \n
forms\, generate I_q^n F.\n
\n
\n
\n
We call a set of quadratic n-fold Pfister forms linked if they all share a \n
common (n-1)-fold Pfister factor. Since we wish to develop a \n
characteristic-free theory\, we need to consider the characteristic 2 case\, \n
where one has to distinguish between right linkage and left linkage.\n
\n
\n
\n
To a certain type of set of s n-fold Pfister forms\, we associate an invariant \n
in I_q^{n+1} F which lives in I_q^{n+s-1} F when the set is linked. We \n
study the properties of this invariant and compute necessary conditions for a \n
set to be linked.\n
\n
\n
\n
We also consider the related notion of linkage for quaternion algebras via \n
linkage of the associated norm forms.\n
\n
http://math.biu.ac.il/files/math/seminars/abstarct_for_seminar-_shira.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2291:field_when:0:28
SUMMARY:Matrices over local rings
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170116T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170116T150500
URL;VALUE=URI:http://math.biu.ac.il/node/2291
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. D. Kerner\, Ben-Gurion University\n
\n
Abstract:\n
Linear algebra over a field have been studied for centuries. In many branches \n
of math one \n
faces matrices over a ring\, these came e.g. as "matrices of functions" or \n
"matrices depending \n
on parameters". Linear algebra over a (commutative\, associative) ring is \n
infinitely more \n
complicated. Yet\, some particular questions can be solved.\n
I will speak about two problems: block-diagonalization (block-diagonal \n
reduction) of matrices \n
and stability of matrices under perturbations by higher-order-terms.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2290:field_when:0:29
SUMMARY:Continuous valuations on convex sets and Monge-Ampere operators
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170109T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170109T173500
URL;VALUE=URI:http://math.biu.ac.il/node/2290
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. S. Alesker\, Tel-Aviv University\n
\n
Abstract:\n
Finitely additive measures on convex convex sets are called valuations. \n
Valuations continuous in\n
the Hausdorff metric are of special interest and have been studied in \n
convexity for a long time.\n
In this talk I will present a non-traditional method of constructing \n
continuous valuations using\n
various Monge-Ampere (MA) operators\, namely the classical complex MA operator \n
and introduced by\n
the speaker quaternionic MA operators (if time permits\, I will briefly \n
discuss also octonionic case).\n
In several aspects analytic properties of the latter are very similar to the \n
properties of the former\,\n
but the geometric meaning is different. The construction of the quaternionic \n
MA operator uses\n
non-commutative determinants.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2286:field_when:0:30
SUMMARY:Banach algebraic geometry
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170111T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170111T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2286
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Oren Ben-Bassat (Haifa University)\n
\n
Abstract:\n
I will talk about two topics which give support to a unified theory of \n
archimedean and non-archimedean analytic geometry. In both examples I will \n
review a topic in complex analytic geometry (results from the 1970's) and\, \n
after reinterpreting it\, show that the same thing happens in non-archimedean \n
geometry (giving new results). The first topic is a non-archimedean version \n
of Ishimura's theorem. This theorem states that on a complex manifold\, the \n
continuous linear endomorphisms of the structure sheaf agrees with the sheaf \n
of formal differential operators whose symbol is holomorphic on the cotangent \n
bundle. The second topic is about acyclicity. On a complex analytic space\, \n
this is about "quasi-coherent sheaves" not having higher cohomology on Stein \n
spaces. I explain a similar result in the non-archimedean context. The tools \n
used involve an interesting mix of homological algebra and functional \n
analysis. I will explain some potential applications of both of these topics \n
related to number theory. No knowledge about cohomology\, differential \n
operators\, Stein spaces\, or any sort of analytic geometry will be assumed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2284:field_when:0:31
SUMMARY:Partitioning a cardinal into fat stationary sets (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170105T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170105T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2284
LOCATION:seminar room
DESCRIPTION:Speaker: Assaf Rinot\n
\n
Abstract:\n
This is a continuation of last week's talk [1]. This time\, I shall prove that \n
square(kappa) give rise to a partition of kappa into kappa many fat sets\n
\n
\n
[1] http://math.biu.ac.il/node/2282
END:VEVENT
BEGIN:VEVENT
UID:calendar:2282:field_when:0:32
SUMMARY:Partitioning a cardinal into fat stationary sets
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161229T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161229T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2282
LOCATION:seminar room
DESCRIPTION:Speaker: Assaf Rinot\n
\n
Abstract:\n
A subset F of a regular uncountable cardinal kappa is said to be /fat /iff \n
for every club C in kappa\, and every ordinal alpha By a theorem of H. \n
Friedman from 1974\, every stationary subset of w1 is fat. In particular\, w1 \n
may be partitioned into w1 many pairwise disjoint fat sets.\n
\n
In this talk\, I shall prove that square(kappa) give rise to a partition of \n
kappa into kappa many pairwise disjoint fat sets. In particular\, the \n
following are equiconsistent:\n
\n
1) w2 cannot be partitioned into w2 many pairwise disjoint fat sets\;\n
2) w2 cannot be partitioned into two disjoint fat sets\;\n
3) there exists a weakly compact cardinal.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2281:field_when:0:33
SUMMARY:Pentagram maps and nondegenerate curves
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170101T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170101T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2281
LOCATION:seminar room
DESCRIPTION:Speaker: Boris Khesin\, University of Toronto\n
\n
Abstract:\n
A plane curve is called nondegenerate if it has no inflection points.\n
\n
How many classes of closed nondegenerate curves exist on a sphere?\n
\n
We are going to see how this geometric problem\, solved in 1970\, reappeared \n
along with its generalizations in the context of the Korteweg-de Vries and \n
Boussinesq equations. Its discrete version is related to the 2D pentagram map \n
defined by R. Schwartz in 1992.\n
\n
We will also describe its generalizations\, pentagram maps on polygons in any \n
dimension and discuss their integrability properties.\n
\n
\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2279:field_when:0:34
SUMMARY:"Small" representations of finite classical groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170201T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170201T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2279
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Shamgar Gurevich (University of Wisconsin and Yale University)\n
\n
Abstract:\n
Suppose you have a finite group G and you want to study certain related \n
structures (e.g.\, random walks\, Cayley graphs\, word maps\, etc.). In many \n
cases\, this might be done using sums over the characters of G. A serious \n
obstacle in applying these formulas is lack of knowledge on the \n
low dimensional representations of G. In fact\, numerics shows that the \n
“small" representations tend to contribute the largest terms to these \n
sums\, so a systematic knowledge of them might assist in the solution of \n
important problems. \n
\n
In this talk I will discuss a joint project (see arXiv:1609.01276) with \n
Roger Howe (Yale). We introduce a language to speak about “size” of a \n
representation\, and we develop a method for systematically construct \n
(conjecturally all the) “small" representations of finite classical \n
groups.\n
\n
I will illustrate our theory with concrete motivations and numerical data \n
obtained with John Cannon (MAGMA\, Sydney) and Steve Goldstein (Scientific \n
computing\, Madison).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2276:field_when:0:35
SUMMARY:On a Formerly New Order Type (part 3)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161215T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161215T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2276
LOCATION:seminar room
DESCRIPTION:Speaker: Thilo Weinert (BGU)\n
\n
Abstract:\n
We are going to prove a classical result of Baumgartner - the existence of a \n
linear order type every uncountable subtype of which contains a copy of \n
omega_1 yet fails to be the union of countably many well-ordered types.\n
\n
The paper may be found in here [1].\n
\n
\n
[1] http://www.sciencedirect.com/science/article/pii/0003484376900012
END:VEVENT
BEGIN:VEVENT
UID:calendar:2275:field_when:0:36
SUMMARY:Exotic Poisson summation formulas
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161219T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161219T154500
URL;VALUE=URI:http://math.biu.ac.il/node/2275
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Nir Lev\, Bar-Ilan University\n
\n
Abstract:\n
By a crystalline measure in R^d one means a measure whose support and \n
spectrum are both discrete closed sets. I will survey the subject and \n
discuss recent results obtained jointly with Alexander Olevskii.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2274:field_when:0:37
SUMMARY:Geometric Incidences and the Polynomial Method
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161218T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161218T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2274
LOCATION:seminar room
DESCRIPTION:Speaker: Adam Sheffer\n
\n
Abstract:\n
While the topic of geometric incidences has existed for several decades\, in \n
recent years it has been experiencing a renaissance due to the introduction \n
of new polynomial methods. This progress involves a variety of new results \n
and techniques\, and also interactions with fields such as algebraic geometry \n
and harmonic analysis.\n
\n
A simple example of an incidences problem: Given a set of n points and set of \n
n lines\, both in R^2\, what is the maximum number of point-line pairs such \n
that the point is on the line. Studying incidence problems often involves the \n
uncovering of hidden structure and symmetries.\n
\n
In this talk we introduce and survey the topic of geometric incidences\, \n
focusing on the recent polynomial techniques and results (some by the \n
speaker). We will see how various algebraic and analysis tools can be used to \n
solve such combinatorial problems.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2273:field_when:0:38
SUMMARY:Involutions of the second kind and ramified double covers
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161228T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161228T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2273
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Uriya First (University of British Columbia)\n
\n
Abstract:\n
Let K/F be a quadratic Galois field extension and let s be the nontrivial \n
F-automorphism of K. A celebrated theorem of Albert characterizes the kernel \n
of the corestriction map Br(K)-->Br(F) as those Brauer classes containing a \n
central simple K-algebra that admits an s-involution\, i.e. an involution \n
whose restriction to K is s.\n
\n
Saltman generalized this result from quadratic Galois extensions \n
of fields to quadratic Galois extension of commutative rings. A later \n
proof given by Knus\, Parimala and Srinivas applies in the greater generality \n
of unramified double covers of schemes.\n
\n
I will discuss a recent work with B. Williams in which we extend the \n
aforementioned results to ramified double covers of schemes (and more \n
generally of locally ringed topoi). Some fascinating phenomena that can occur \n
only in the ramified case will also be discussed. For example\, the classical \n
construction of the corestriction of an Azumaya algebra does produce an \n
Azumaya algebra when the corestriction is taken relative to a ramified double \n
cover (so one cannot use it in proving our result).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2270:field_when:0:39
SUMMARY:On a Formerly New Order Type (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161208T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161208T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2270
LOCATION:seminar room
DESCRIPTION:Speaker: Thilo Weinert (BGU)\n
\n
Abstract:\n
Abstract: We are going to prove a classical result of Baumgartner - the \n
existence of a linear order type every uncountable subtype of which contains \n
a copy of omega_1 yet fails to be the union of countably many well-ordered \n
types.\n
\n
The paper may be found in here [1].\n
\n
\n
[1] http://www.sciencedirect.com/science/article/pii/0003484376900012
END:VEVENT
BEGIN:VEVENT
UID:calendar:2269:field_when:0:40
SUMMARY:Arithmetic statistics in function fields
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161211T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161211T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2269
LOCATION:seminar room
DESCRIPTION:Speaker: Edva Roditty-Gershon\, Bristol University\n
\n
Abstract:\n
In the talk I will discuss classical problems concerning the distribution \n
of square-full numbers and their analogues over function fields. The results \n
described are in the context of the ring Fq[T ] of polynomials over a \n
finite field Fq of q elements\, in the limit q → ∞. \n
\n
I will also present some recent generalization of these kind of \n
classical problems.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2268:field_when:0:41
SUMMARY:The congruence subgroup problem for automorphism groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161221T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161221T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2268
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: David El-Chai Ben-Ezra (Hebrew University of Jerusalem)\n
\n
Abstract:\n
See attached file.\n
\n
http://math.biu.ac.il/files/math/seminars/abstract2.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2267:field_when:0:42
SUMMARY:Doubling global constructions for tensor product L-functions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161214T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161214T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2267
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Eyal Kaplan (Bar-Ilan University)\n
\n
Abstract:\n
I will present a joint work with Cai\, Friedberg and Ginzburg. \n
\n
In a series of constructions\, we apply the ``doubling method"\n
\n
from the theory of automorphic forms to covering groups. \n
\n
We obtain partial tensor product L-functions attached to generalized Shimura \n
lifts\, \n
\n
which may be defined in a natural way since at almost all places the \n
representations \n
\n
are unramified principal series.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2266:field_when:0:43
SUMMARY:On a Formerly New Order Type
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161201T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161201T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2266
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Thilo Weinert (BGU)\n
\n
Abstract: We are going to prove a classical result of Baumgartner - the \n
existence of a linear order type every uncountable subtype of which contains \n
a copy of omega_1 yet fails to be the union of countably many well-ordered \n
types.\n
The paper may be found in here [1].\n
\n
\n
[1] http://www.sciencedirect.com/science/article/pii/0003484376900012
END:VEVENT
BEGIN:VEVENT
UID:calendar:2265:field_when:0:44
SUMMARY:More on Differential Inequalities and Normality
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161205T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161205T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2265
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Tomer Manket\, Bar-Ilan University\n
\n
Abstract:\n
Differential inequalities and their connection to normality (and quasi \n
normality) have been studied since Marty’s Theorem in 1935. We discuss when \n
these inequalities imply some degree of normality\, and present a new result\, \n
joint with S. Nevo and J. Grahl.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2262:field_when:0:45
SUMMARY:Differential inequalities and normality
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161128T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161128T155500
URL;VALUE=URI:http://math.biu.ac.il/node/2262
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Shahar Nevo\, Bar-Ilan University\n
\n
Abstract:\n
Following Marty's Theorem we present recent results about differential \n
inequalities that imply (or not) some degree of normality. We deal with \n
inequalities with reversed sign of inequality than that in Marty's Theorem\, \n
i.e. $|f^(k)(z)|> h(|f(z))$.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2261:field_when:0:46
SUMMARY:An application of group theory to topology
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161207T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161207T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2261
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. George Glauberman (University of Chicago)\n
\n
Abstract:\n
Let p be a prime. To every finite group is associated a topological\n
space known as the p-completion of its classifying space. The\n
Martino-Priddy conjecture states that for two groups G and H\, these\n
spaces are homotopically equivalent if and only if there is a special\n
type of isomorphism between the Sylow p-subgroups of G and H\n
(an isomorphism of fusion systems\, e.g.\, elements conjugate in G\n
are mapped to elements conjugate in H).\n
The combined work of several authors has proved this conjecture\n
and some extensions\, partly by assuming the classification of\n
finite simple groups. Recently\, J. Lynd and I removed this assumption.\n
I plan to discuss the main ideas of these results.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2259:field_when:0:47
SUMMARY:Differential inequalities and normality
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161128T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161128T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2259
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Shahar Nevo\, Bar-Ilan University\n
\n
Abstract:\n
Following Marty's Theorem we present recent results about differential \n
inequalities that imply (or not) some degree of normality. We deal with \n
inequalities with reversed sign of inequality than that in Marty's Theorem\, \n
i.e. $|f^(k)(z)|> h(|f(z))$.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2257:field_when:0:48
SUMMARY:Finite subsets of the first uncountable ordinal (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161124T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161124T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2257
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Eran Stein\n
\n
Abstract:\n
Last week\, we presented a construction scheme which is based on well-behaving \n
delta-systems of finite subsets of w1. In this lecture\, we shall present an \n
application to the theory of uncountable trees.\n
\n
The results are taken from the following paper [1].\n
\n
\n
[1] https://arxiv.org/abs/1602.01518
END:VEVENT
BEGIN:VEVENT
UID:calendar:2256:field_when:0:49
SUMMARY:Hindman’s theorem and uncountable Abelian groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161127T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161127T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2256
LOCATION:seminar room
DESCRIPTION:Speaker: Assaf Rinot\n
\n
Abstract: In the early 1970's\, Hindman proved a beautiful theorem in additive \n
Ramsey theory asserting that for any partition of the set of natural numbers \n
into finitely many cells\, there exists some infinite set such that all of its \n
finite sums belong to a single cell. In this talk\, we shall study \n
generalizations of this statement. Among other things\, we shall present a \n
negative partition relation for the real line which simultaneously \n
generalizes a recent theorem of Hindman\, Leader and Strauss\, and a classic \n
theorem of Galvin and Shelah. This is joint work [1] with D.J. Fernandez \n
Breton from the University of Michigan.\n
\n
[1] http://www.assafrinot.com/paper/27
END:VEVENT
BEGIN:VEVENT
UID:calendar:2255:field_when:0:50
SUMMARY:Hecke-Hopf algebras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161120T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161120T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2255
LOCATION:Seminar room
DESCRIPTION:Speaker: Prof. Arkady Berenstein\, University of Oregon\n
\n
Abstract:\n
Hecke algebras H_q(W) of Coxeter groups W first emerged in the study of \n
Chevalley groups in mid sixties and since then became central objects in \n
Representation Theory of Coxteter groups and semisimple Lie groups over \n
finite fields. In particular\, as a one-parameter deformation of the group \n
algebra kW of W\, the Hecke algebra H_q(W) helps to classify representations \n
of W and to equip each simple kW-module with the canonical Kazhdan-Lusztig \n
basis.\n
Unfortunately\, unlike the group algebra kW\, the Hecke algebra H_q(W) lacks a \n
Hopf algebra structure\, that is\, it is not clear how to tensor multiply \n
H_q(W)-modules. Moreover\, there is a general consensus that a naive Hopf \n
structure on H_q(W)\, if exists\, would essentially coincide with that on kW\, \n
so we would not gain any new information.\n
In my talk (based on joint work with D. Kazhdan) I suggest a roundabout: \n
instead of forcing a naive Hopf structure on H_q(W)\, we find a ``reasonably \n
small" Hopf algebra H(W) (we call it Hecke-Hopf algebra of W) that \n
"naturally" contains H_q(W) as a coideal subalgebra.\n
The immediate benefit of this enlargement of H_q(W) is that each \n
representation of H(W) and each representation of H_q(W) can be tensor \n
multiplied into a new representation of H_q(W)\, thus allowing to create \n
infinitely many new H_q(W)-modules out of a single one.\n
Hecke-Hopf algebras have some other applications\, most spectacular of which \n
is the construction of new infinite families of solutions to the quantum \n
Yang-Baxter equation.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2240:field_when:0:51
SUMMARY:On the Gelfand-Kazhdan criterion and the commutativity of Hecke algebras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161123T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161123T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2240
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Yotam Hendel (Weizmann Institute of Science)\n
\n
Abstract:\n
For a finite group G and a subgroup H\, we say that (G\,H) is a Gelfand pair if \n
the decomposition of C[G/H]\, the G-representation of complex-valued functions \n
on G/H\, into irreducible components has multiplicity one. In this case\, the \n
Gelfand property is equivalent to the commutativity of the Hecke algebra \n
C[H\G/H] of bi-H-invariant functions on G. \n
\n
Given a reductive group G and a closed subgroup H\, there are three standard \n
ways to generalize the notion of a Gelfand pair\, and a result of Gelfand and \n
Kazhdan gives a sufficient condition under which two of these properties \n
hold. Unfortunately\, in contrast to the finite case\, here the Gelfand \n
property is not known to be equivalent to the commutativity of a Hecke \n
algebra. In this talk we define a Hecke algebra for the pair (G\,H) in the \n
non-Archimedean case and show that if the Gelfand-Kazhdan conditions hold \n
then it is commutative. We then explore the connection between the \n
commutativity of this algebra and the Gelfand property of (G\,H).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2254:field_when:0:52
SUMMARY:Finite-dimensional representations of quantum affine algebras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161130T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161130T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2254
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Jianrong Li (Weizmann Institute of Science)\n
\n
Abstract:\n
In this talk\, I will discuss finite dimensional representations of quantum \n
affine algebras. The main topics are Chari and Presslay's classification of \n
finite-dimensional simple modules over quantum affine algebras\, Frenkel and \n
Reshetikhin's theory of q-characters of finite dimensional modules\, \n
Frenkel-Mukhin algorithm to compute q-characters\, T-systems\, \n
Hernandez-Leclerc's conjecture about the cluster algebra structure on the \n
ring of a subcategory of the category of all finite dimensional \n
representations of a quantum affine algebra. I will also talk about how to \n
obtain a class of simple modules called minimal affinizations of types A\, B \n
using mutations (joint work with Bing Duan\, Yanfeng Luo\, Qianqian Zhang).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2253:field_when:0:53
SUMMARY:Asymptotic relations for the Fourier transform of a function of bounded \n
variation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161121T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161121T151500
URL;VALUE=URI:http://math.biu.ac.il/node/2253
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. E. Liflyand\, Bar-Ilan University\n
\n
Abstract:\n
Earlier and recent one-dimensional estimates and asymptotic relations for the\n
cosine and sine Fourier transform of a function of bounded variation are \n
refined\n
in such a way that become applicable for obtaining multidimensional \n
asymptotic\n
relations for the Fourier transform of a function with bounded Hardy \n
variation.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2252:field_when:0:54
SUMMARY:Boundary triples and Weyl functions of symmetric operators
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161114T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161114T153500
URL;VALUE=URI:http://math.biu.ac.il/node/2252
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. V. Derkach\, Vasyl Stus Donetsk University\, Ukraine\n
\n
Abstract:\n
Selfadjoint extensions of a closed symmetric operator A in a Hilbert\n
space with equal de ficiency indices were described by in the 30s by\n
J. von Neumann. Another approach\, based on the notion of abstract boundary\n
triple originates to the works of J.W. Calkin and was developed by M.I. \n
Visik\,\n
G.Grubb\, F.S.Rofe-Beketov\, M.L.Gorbachuck\, A.N.Kochubei and others.\n
By Calkin's approach all selfadjoint extensions of the symmetric operator A \n
can\n
be parametrized via "multivalued" selfadjoint operators in an auxiliary \n
Hilbert spaces.\n
Spectral properties of these extensions can be characterized in terms of the \n
abstract\n
Weyl function\, associated to the boundary triple. In the present talk some \n
recent\n
developments in the theory of boundary triples will be presented. \n
Applications to\n
boundary value problems for Laplacian operator in bounded domains with smooth \n
and\n
rough boundaries will be discussed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2145:field_when:0:55
SUMMARY:The colouring number of infinite graphs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160620T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160620T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2145
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Omri Marcus\n
\n
Abstract:\n
We show that every graph with inﬁnite colouring number has a well-ordering \n
of its vertices that simultaneously witnesses its colouring number and its \n
cardinality.\n
\n
The lecture will be based on the following paper [1].\n
\n
\n
[1] http://arxiv.org/abs/1512.02911
END:VEVENT
BEGIN:VEVENT
UID:calendar:2242:field_when:0:56
SUMMARY:An anti-Hindman theorem for the real line
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161108T090000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161108T110000
URL;VALUE=URI:http://math.biu.ac.il/node/2242
LOCATION:Room 201
DESCRIPTION:Speaker: Dani Livne\n
\n
Abstract:\n
We present Komjath's theorem that there exists a coloring of the real line in \n
2 colors such that for any uncountable subset A of reals\, there exist 4 \n
distinct elements a\,b\,c\,d in A such that a+b gets color 0\, and c+d gets color \n
1.\n
\n
The results are taken from the following paper [1].\n
\n
\n
[1] http://www.cs.elte.hu/~kope/p66.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2251:field_when:0:57
SUMMARY:Finite subsets of the first uncountable ordinal
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161115T090000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161115T110000
URL;VALUE=URI:http://math.biu.ac.il/node/2251
LOCATION:seminar room
DESCRIPTION:Speaker: Eran Stein\n
\n
Abstract:\n
We present a construction scheme which is based on well-behaving \n
delta-systems of finite subsets of w1\, and use it to construct uncountable \n
trees.\n
\n
The results are taken from the following paper [1].\n
\n
\n
[1] https://arxiv.org/abs/1602.01518
END:VEVENT
BEGIN:VEVENT
UID:calendar:2250:field_when:0:58
SUMMARY:On the classification of quadratic forms over an integral domain of a global \n
function field
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161116T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161116T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2250
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Rony Bitan (Bar-Ilan University)\n
\n
Abstract:\n
Let C be a smooth projective curve defined over the finite field F_q (q is \n
odd)\n
\n
and let K=F_q(C) be its (global) function field. \n
\n
Any finite set S of closed points of C gives rise to a Dedekind domain \n
O_S:=F_q[C-S] in K. \n
\n
We show that given an O_S-regular quadratic space (V\,q) of rank n >= 3\, \n
\n
the group Br(O_S)[2] is bijective to the set of genera in the proper \n
classification of quadratic O_S-spaces \n
\n
isomorphic to V\,q for the \'etale topology\, thus there are 2^{|S|-1} such. \n
\n
\n
If (V\,q) is isotropic\, then Pic(O_S)/2 properly classifies the forms in the \n
genus of (V\,q). \n
\n
This is described concretely when V is split by an hyperbolic plane\, \n
\n
including an explicit algorithm in case C is an elliptic curve. \n
\n
For n >= 5 this is true for all genera hence the full classification is via \n
the abelian group H^2_et(O_S\,\mu_2).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2249:field_when:0:59
SUMMARY:Selection Priniciples in Mathematics (an overview)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161113T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161113T182000
URL;VALUE=URI:http://math.biu.ac.il/node/2249
LOCATION:seminar room
DESCRIPTION:Speaker: Piotr Szewczak\n
\n
Abstract:\n
The theory of selection principles deals with the possibility of obtaining \n
mathematically significant objects by selecting elements from sequences of \n
sets. The studied properties mainly include covering properties\, measure- and \n
category-theoretic properties\, and local properties in topological spaces\, \n
especially functions spaces. Often\, the characterization of a mathematical \n
property using selectionprinciple is a nontrivial task leading to new \n
insights on the characterized property.\n
\n
I will give an overview of this theory and\, if time permits\, present some \n
resent results obtained jointly with Boaz Tsaban and Lyubomyr Zdomskyy.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2244:field_when:0:60
SUMMARY:(Fuglede's tiling-spectrality conjecture. (ERC project
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161106T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161106T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2244
LOCATION:(Colloquium room (building 216
DESCRIPTION:Speaker: Nir Lev\, Dept. of Mathematics\, Bar-Ilan University\n
\n
Abstract:\n
We know by classical Fourier analysis that the unit cube in R^d has an \n
orthogonal basis consisting of exponential functions. Which other domains \n
admit such a basis? Fuglede conjectured (1974) that these so-called "spectral \n
domains" could be characterized geometrically by their possibility to tile \n
the space by translations. I will survey the subject and then discuss some \n
recent results\, joint with Rachel Greenfeld\, where we focus on the conjecture \n
for convex polytopes.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2230:field_when:0:61
SUMMARY:Totally decomposable involutions and quadratic pairs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161027T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20161027T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2230
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Andrew Dolphin (Universiteit Antwerpen)\n
\n
Abstract:\n
Determining whether a central simple algebra is isomorphic to the tensor \n
product of quaternion algebras is a classical question. One can also ask \n
similar decomposability questions when there is additional structure defined \n
on the central simple algebra\, for example an involution. We may ask whether \n
an involution on a central simple algebra is isomorphic to the tensor product \n
of involutions defined on quaternion algebras\, i.e. whether the involution is \n
totally decomposable. \n
\n
Algebras with involution can be viewed as twisted symmetric bilinear forms \n
up to similarity\, and hence also as twisted quadratic forms up to similarity \n
if the characteristic of the underlying field is different from 2. In a paper \n
of Bayer\, Parimala and Quéguiner it was suggested that totally \n
decomposable involutions could be a natural generalisation of Pfister forms\, \n
a type of quadratic form of central importance to the modern theory of \n
quadratic forms. In this talk we will discuss recent progress on the \n
connection between totally decomposable involutions and Pfister forms. \n
\n
We will also discuss fields of characteristic 2\, where\, since symmetric \n
bilinear forms and quadratic forms are no longer equivalent\, involutions are \n
not twisted quadratic forms. Instead\, if one wants a notion of a twisted \n
quadratic form with analogous properties to involutions\, one works \n
with objects introduced in the Book of Involutions\, known as a quadratic \n
pairs. One can define an analogous notion of total decomposability for \n
quadratic pairs\, and there is a connection to Pfister forms very similar to \n
that found between involutions and Pfister forms in characteristic different \n
from 2.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2143:field_when:0:62
SUMMARY:סולמות זמנים שמשיים ו'משוואת הזמן' \n
באסטרונומיה המודרנית ובזו של הקדמונים
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160621T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160621T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2143
LOCATION:חדר המחלקה של המחלקה למתמטיקה \n
שבאוניברסיטת בר- אילן (בנין מספר 216)\, קומה \n
עליונה.
DESCRIPTION:Speaker: מהנדס יעקב לוינגר\n
\n
Abstract:\n
\n
\n
*מושגי יסוד* אסטרונומיים הקשורים בהגדרת \n
*הזמן השמשי* לסוגיו\,\n
\n
*מערכות קואורדינטות* למיקום גרמי השמים על \n
ספֵרת השמים:\n
\n
* *קואורדינטות המִלקה* **קואורדינטות \n
משווניות*\n
\n
*קואורדינטות האופק*:\n
\n
*שתי השמשות הנעות* על ספֵרת השמים ומהירות \n
תנועותיהן\,\n
\n
הגדרת '*הזמן האמתי'* ו'*הזמן הממוצע' *\n
\n
הגדרת *'משוואת *(= השוואת) *הזמן'*\n
\n
הכינוי *'משוואת אורך היממה'* של הקדמונים\, \n
במקום המונח 'משוואת הזמן'\,\n
\n
*גרף 'משוואת הזמן'* המודרנית וזו של \n
הקדמונים\, וערכיהן הקיצוניים\,\n
\n
לאילו *מטרות חישוביות* משמשת אותנו 'משוואת \n
הזמן' \n
\n
שתי מהפכות גדולות במניית הזמן\, באמצעות \n
'משוואת הזמן':\n
\n
התפשטות השימוש ב*שעונים מכניים *החל מהמאה \n
ה-14\,\n
\n
המצאת *סולם 'הזמן הממוצע המודרני'\,* בסוף \n
המאה ה-17\n
\n
שני סוגי סולם 'זמן ממוצע' של הקדמונים:\n
\n
סולם זמן ממוצע מהסוג שבאלמגסט (Almagest) של \n
תלמי\, ובחיבורו של אל בתאני\,\n
\n
סולם זמן ממוצע של מהסוג שב'לוחות על יד' (Handy \n
Tables) של תלמי\,\n
\n
סולם *הזמן הממוצע של הלוח העברי* – הדעות \n
העיקריות בנידון\,\n
\n
*סולם הזמן של רמב''ם* לחישוב ערכי ה'עיקר' \n
שלו\, בהלכות קידוש החודש\,\n
\n
מקורות\n
\n
*מצגת ההרצאה [1]*\n
\n
*להרצאה המצולמת* [2]\n
\n
\n
[1] http://u.math.biu.ac.il/~esheds/levinger 21.6.16.pdf\n
[2] https://www.youtube.com/watch?v=Y39w9hDMjfE&\;list=PLXF_IJaFk-9DWxOnG84eMXOxwxhpQY6D-&\;index=11
END:VEVENT
BEGIN:VEVENT
UID:calendar:2149:field_when:0:63
SUMMARY:The colouring number of infinite graphs (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160630T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160630T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2149
LOCATION:seminar room
DESCRIPTION:Speaker: Omri Marcus\n
\n
Abstract:\n
We shall complete the verification of existence of obligatory graphs for \n
infinite colouring numbers.\n
In our previous talk [1]\, we covered the case of graphs of regular \n
cardinality. This time\, we shall address graphs of singular cardinality.\n
\n
\n
[1] http://math.biu.ac.il/node/2145
END:VEVENT
BEGIN:VEVENT
UID:calendar:2147:field_when:0:64
SUMMARY:A two-phase mother body and a Muskat problem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160620T150500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160620T160000
URL;VALUE=URI:http://math.biu.ac.il/node/2147
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Tatiana Savina Ohio University\, Athens\, OH\, USA\n
\n
Abstract:\n
A Muskat problem describes an evolution of the interface $\Gamma \n
(t)\subset{\mathbb R}^{2}$ between two immiscible fluids\, occupying \n
regions $\Omega _1$ and $\Omega _2$ in a Hele-Shaw cell. The \n
interface evolves due to the presence of sinks and sources located in \n
$\Omega _j$\, $j=1\,2$.\n
The case where one of the fluids is effectively inviscid\, that is\, it has a \n
constant pressure\, is called\n
one-phase problem. This case has been studied extensively. Much less \n
progress has been made for the two-phase problem\, the Muskat problem.\n
The main difficulty of the two-phase problem is the fact that the pressure on \n
the interface\, separating the fluids\, is unknown. In this talk we introduce \n
a notion of a two-phase mother body (the terminology comes from the potential \n
theory) as a union of two distributions $\mu _j$ with integrable densities \n
of sinks and sources\, allowing to control the evolution of the interface\, \n
such that $\rm{supp}\\, \mu _j \subset\Omega _j$. We use the Schwarz function \n
approach and the introduced two-phase mother body to find the evolution of \n
the curve $\Gamma (t)$ as well as two harmonic functions $p_j$\, the \n
pressures\, defined almost everywhere in $\Omega_j$ and satisfied \n
prescribed boundary conditions on $\Gamma (t)$.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2146:field_when:0:65
SUMMARY:Spectrality and tiling by cylindric domains
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160620T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160620T150000
URL;VALUE=URI:http://math.biu.ac.il/node/2146
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Rachel Greenfeld Bar-Ilan University\n
\n
Abstract:\n
A bounded set O in R^d is called spectral if the space L^2(O) admits an \n
orthogonal basis consisting of\n
exponential functions. In 1974 Fuglede conjectured that spectral sets can be \n
characterized geometrically\n
by their ability to tile the space by translations. Although since then \n
spectral sets have been intensively\n
studied\, the connection between spectrality and tiling is still unresolved in \n
many aspects.\n
I will focus on cylindric sets and discuss a new result\, joint with Nir Lev\, \n
on the spectrality of such sets.\n
Since also the tiling analogue of the result holds\, it provides a further \n
evidence of the strong connection\n
between these two properties.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2121:field_when:0:66
SUMMARY:זמן התפילה בהנץ החמה - הנץ המישורי או \n
הנראה?
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160524T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160524T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2121
LOCATION:חדר מחלקה
DESCRIPTION:Speaker: הרב יואל שילה\n
\n
Abstract:\n
תחילת זמן ק"ש משיכיר את חברו - שהוא זמן \n
הקימה\n
תחילת זמן תפילת שחרית לכתחילה לא התפרש \n
בגמרא\, ונחלקו בזה הראשונים והפוסקים\n
תפילה כוותיקין לרוב הראשונים היא מעלה \n
בעלמא\, שזהו עת רצון\, והיא מתקיימת \n
כשמתחילים את התפילה בהנץ החמה.\n
הנץ החזל"י בודאי איננו האסטרונומי\, כלומר \n
כשאמצע החמה עולה מעל האופק\, תוך חישוב \n
הרפרקציה\, אלא הוא כשתחילת גוף החמה מציץ \n
מעל האופק לעינינו.\n
לעומד בראש ההר - הזריחה מקדימה\, ונחלקו האם \n
יחשיב את הרגע שרואה אותה כזריחה\, או \n
שמתחשבים בעומדים במישור שמתחתיו.\n
לעומד בבקעה\, וכן לעומד במישור כשאופק מזרח \n
שלו מוסתר - ראיית החמה מתאחרת\, ונחלקו האם \n
ימתין עד שיראה את החמה בפועל\, או שיתפלל \n
כשהחמה היתה נראית אלמלא ההסתרה.\n
יש שהוכיחו מסוגיית הנברשת ומהתוספתא של \n
חמה מטפטפת - שיש להמתין.\n
ולענ"ד - אין שום ספק שהזמן הקובע הוא \n
המישורי.\n
\n
*להרצאה המצולמת [1]*\n
\n
*למצגת ההרצאה* [2]\n
\n
\n
[1] https://youtu.be/1py66uQ1LRY\n
[2] http://u.math.biu.ac.il/~esheds/shilo.ppt
END:VEVENT
BEGIN:VEVENT
UID:calendar:2123:field_when:0:67
SUMMARY:הדמיון בין חשיבות הנתונים האסטרונומיים \n
המתייחסים לנקודות העיקר של הלוח ההינדי \n
ושל הלוח העברי אצל אל-חוואריזמי
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160503T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160503T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2123
LOCATION:חדר מחלקה
DESCRIPTION:Speaker: פרופ' אריאל כהן\, האוניברסיטה העברית\n
\n
Abstract:\n
הלוח ההינדי מכיל מחזורים בני 432000 ואף 4320000 \n
שנים סידריות שבתחילת כל אחד מהם מתחדש \n
העולם על-פי תפיסתם. כך\, למשל\, השנה 3102 לפני \n
ספירת הנוצרים היא השנה של תחילת המחזור \n
הנוכחי – "הקאלי יוגה"\, ובשנה זו עפ"י האמונה \n
הרווחת שם קרישנה נעלם במרכבה לשמים לאחר \n
שירד המבול. אולם העובדה המדעית עליה \n
התבססו ההינדים כדי לחשב את תחילת המחזורים \n
הארוכים בהתאם ליידע המדעי שלהם הייתה \n
שבתחילת המחזור חזרו כל כוכבי הלכת ובכללם \n
השמש והירח לאותן הקואורדינטות השמימיות. \n
אנו נראה כי הטבלה המופיעה אצל אל-חוואריזמי \n
המתייחסת לנתונים האסטרונומיים של אותם \n
כוכבי לכת בשנת הבריאה של הלוח העברי \n
מסודרים אף הם בסדר מופתי. \n
כמו-כן נראה כי מיקום השמש והירח עפ"י הטבלה \n
האסטרונומית של אל-חוואריזמי חוזר על עצמו \n
במדוייק במחזורים קטנים יותר אך כאלה \n
המתאימים לאירועים המרכזיים של התחדשות \n
בתולדות עם ישראל עפ"י התנ"ך.\n
\n
*מצגת ההרצאה [1]*\n
\n
*להרצאה המצולמת [2]\n
[3]*\n
\n
\n
[1] http://u.math.biu.ac.il/~esheds/3.5.2016.pdf\n
[2] https://youtu.be/7JzknNud2Ec\n
[3] http://u.math.biu.ac.il/~esheds/3.5.2016.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2142:field_when:0:68
SUMMARY:Signed Hultman numbers and generalized commuting probability in finite groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160619T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160619T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2142
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Robert Shwartz (Ariel University)\n
\n
Abstract:\n
Let $G$ be a finite group\, and let $\pi$ be a permutation from $S_n$. We \n
study the distribution of probabilities of the equality\n
\n
\[ a_1 a_2 \cdots a_n = a_{\pi_1}^{\epsilon_1} a_{\pi_2}^{\epsilon_2} \cdots \n
a_{\pi_n}^{\epsilon_n}\, \]\n
\n
where $\pi$ varies over all the permutations in $S_n$\, and $\epsilon_i$ \n
varies either over the set $\{1\, -1\}$ or over the set $\{1\, b\}$\, where \n
$b$ is an involution in $G$ (two different cases of equations). The \n
equation can also be written as\n
\n
\[ a_1 a_2 \cdots a_n = a_{\pi_1} a_{\pi_2} \cdots a_{\pi_n}\, \]\n
\n
where $\pi$ is a signed permutation from $B_n$\, and $a_{-i}$ is interpreted \n
either as the inverse $a_i^{-1}$\, in case $\epsilon_i \in \{1\, -1\}$\, or as \n
the conjugate $b a_i b$\, in case $\epsilon_i \in \{1\, b\}$. The probability \n
in the second case depends on the conjugacy class of the involution $b$.\n
\n
First we consider the case in which all $\epsilon_i$ are $1$. It turns out \n
that the probability\, for a permutation $\pi$\, depends only on the number of \n
alternating cycles in the cycle graph of $\pi$\, introduced by Bafna and \n
Pevzner in 1998. We describe the spectrum of probabilities of permutation \n
equalities in a finite group as $\pi$ varies over all permutations \n
in $S_n$. We then generalize\, letting a signed permutation vary over all \n
the signed permutations in $B_n$\, under the two interpretations outlined \n
above. The spectrum turns out to be closely related to the partition of the \n
number $2^{n}\cdot n!$ into a sum of the corresponding signed Hultman \n
numbers (defined by Grusea and Labbare) when $\epsilon_i \in \{1\, -1\}$\, or \n
into edge-signed Hultman numbers (introduced in this talk) when $\epsilon_i \n
\in \{1\, b\}$.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2139:field_when:0:69
SUMMARY:About Sign-Constancy of Green's Function of Two-Point Problem for Impulsive \n
Second Order Delay Equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160619T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160619T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2139
LOCATION:Math building 216\, Seminar room 201
DESCRIPTION:Speaker: Guy Landsman\, BIU\n
\n
Abstract:\n
\n
\n
In our research we consider the linear second order differential \n
equation with delay and impulses. We build Green's functions for the \n
two-point boundary conditions problem. Using Green's functions we find \n
necessary and sufficient conditions of positivity of Green's functions for \n
this impulsive equation coupled with two-point boundary conditions in the \n
form of theorems about differential inequalities.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2138:field_when:0:70
SUMMARY:The generation problem in the Thompson group F
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160615T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160615T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2138
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Gili Golan (Vanderbilt University)\n
\n
Abstract:\n
We show that the generation problem in the Thompson group F is decidable\, \n
i.e.\, there is an algorithm which decides whether a finite set of elements of \n
F generates the whole F. The algorithm makes use of the Stallings 2-core of \n
subgroups of F\, which can be defined in an analogous way to the Stallings \n
core of subgroups of a free group. An application of the algorithm shows that \n
F is a cyclic extension of a group K which has a maximal elementary amenable \n
subgroup B. The group B is a copy of a subgroup of F constructed by Brin.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2125:field_when:0:71
SUMMARY:Clifford algebras of O_X-quadratic spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160601T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160601T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2125
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Patrice Ntumba (University of Pretoria)\n
\n
Abstract:\n
In the classical theory of quadratic forms and Clifford algebras\, it is a \n
well-known result that\, given a finitely generated projective module P\, if \n
H[P] denotes the associated hyperbolic space of P\, then the (graded) algebras \n
Cl(H[P]) and End(^(P)) are isomorphic. We investigate the conditions under \n
which a counterpart of this result holds in the sheaf-theoretic context. \n
Next\, we introduce standard involutions for O_X-algebras associated with \n
K-algebras\, where K is a unital commutative ring with no zero-divisors for \n
the purpose of defining graded quadratic extensions of the ringed space (X\, \n
O_X)\, where X = Spec K.\n
\n
This is joint work with C. Ndipingwi.\n
\n
Also see the attached file.\n
\n
http://math.biu.ac.il/files/math/seminars/2016biu_talk.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2133:field_when:0:72
SUMMARY:Ramsey theory of cardinals\, ordinals\, trees\, and partial orders
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160619T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160619T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2133
LOCATION:seminar room
DESCRIPTION:Speaker: Ari Meir Brodsky\n
\n
Abstract:\n
We explore results of Ramsey theory (also known as partition calculus) and \n
show how they apply to cardinals\, ordinals\, trees\, and arbitrary partial \n
orders\, leading up to the main result [1] which is a generalization to trees \n
of the Balanced Baumgartner-Hajnal-Todorcevic Theorem.\n
\n
\n
\n
A full exposition of the results is contained in my PhD thesis\, available at \n
http://hdl.handle.net/1807/68124 [2].\n
\n
http://math.biu.ac.il/files/math/seminars/brodsky-abstract-biu-colloquium-june2016.pdf\n
\n
[1] http://math.biu.ac.il/files/math/seminars/brodsky-abstract-biu-colloquium-june2016.pdf\n
[2] http://hdl.handle.net/1807/68124
END:VEVENT
BEGIN:VEVENT
UID:calendar:2129:field_when:0:73
SUMMARY:Rigid trees vs. homogeneous trees
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160530T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160530T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2129
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Guy Kapon\n
\n
Abstract:\n
A tree is said to be rigid if it has a trivial automorphism group. It is said \n
to be homogeneous if any two nodes of the same level can be sent one to the \n
other via an automorphism of the tree. In this talk\, we shall present \n
Larson's proof that the existence of a strongly homogeneous Souslin tree \n
entails the existence of a strongly rigid Souslin tree.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2128:field_when:0:74
SUMMARY:Orbits and invariants of the unitriangular group
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160529T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160529T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2128
LOCATION:seminar room
DESCRIPTION:Speaker: Dr. Victoria Sevostyanova (Haifa U.)\n
\n
Abstract:\n
Hilbert’s fourteenth problem asks whether the algebra of invariants for an \n
action of a linear algebraic group is finitely generated.\n
This is true for reductive groups and the problem is open for unipotent \n
groups. We discuss the case of the adjoint action of a maximal unipotent \n
subgroup U in GL_n(K) on the nilradical m of any parabolic subalgebra\, where \n
K is an algebraically closed field of zero characteristic. This action is \n
extended to a representation in the algebra K[m]. I will show that the \n
algebra of invariants K[m]^U is finitely generated. Besides\, a set of \n
algebraically independent invariants generating the field K(m)^U will be \n
presented.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2124:field_when:0:75
SUMMARY:On pointwise domination of Calderon-Zygmund operators by sparse operators
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160530T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160530T151000
URL;VALUE=URI:http://math.biu.ac.il/node/2124
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. A. Lerner\, Bar-Ilan University\n
\n
Abstract:\n
In this talk we survey several recent results establishing a pointwise \n
domination of Calder\'on-Zygmund \n
operators by sparse operators defined by\n
$${\mathcal A}_{\mathcal S}f(x)=\sum_{Q\in {\mathcal \n
S}}\Big(\frac{1}{|Q|}\int_Qf\Big)\chi_{Q}(x)\,$$\n
where ${\mathcal S}$ is a sparse family of cubes from ${\mathbb R}^n$.\n
In particular\, we present a simple proof of M. Lacey's theorem about \n
Calder\'on-Zygmund operators\n
with Dini-continuous kernels in its quantitative form obtained by T. \n
Hyt\"onen-L. Roncal-O. Tapiola.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2122:field_when:0:76
SUMMARY:A Stable Algorithm for Matrix Exponent Calculation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160526T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160526T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2122
LOCATION:Math building 216\, Seminar room 201
DESCRIPTION:Speaker: Teddy Lezebnik - BIU\n
\n
Abstract:\n
\n
\n
We propose a numerical algorithm for calculation of the matrix exponential\, \n
which is stable for every matrix and any number of required signficiant \n
digits. The algorithm is based on the Lanczos method of eigenvalue \n
calculation. Theoretical analysis and proof of stability of the algorithm is \n
given. \n
\n
Joint work with Shlomo Yanetz and Gregory Agranovich (Ariel)
END:VEVENT
BEGIN:VEVENT
UID:calendar:2118:field_when:0:77
SUMMARY:The Ostaszewski space (part 2)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160523T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160523T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2118
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Eran Stein\n
\n
Abstract:\n
We shall resume the presention of Ostaszewski's construction of a perfectly \n
normal\, hereditarily separable\, first countable\, locally countable\, locally \n
compact\, Hausdorff topological space in which every open set is either \n
countable or co-countable.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2120:field_when:0:78
SUMMARY:Set-indexed processes and integration
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160522T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160522T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2120
LOCATION:seminar room
DESCRIPTION:Speaker: Erick Herbin\, Ecole Centrale Paris\n
\n
Abstract:\n
We consider the issue of generalized stochastic processes\, indexed by an \n
abstract set of indices. What should the minimal required conditions on the \n
indexing collection be\, to study some of the usual properties of these \n
processes\, such as in- crement stationarity\, martingale and Markov properties \n
or integration question? The already known examples of processes indexed by \n
functions or metric spaces can be addressed by this way. \n
\n
We show how the set-indexed framework of Ivanoff-Merzbach allows to study \n
these generalized processes.\n
\n
Some set-indexed processes can be considered as random measures on some δ- \n
ring. Some generalized processes can be defined as an integral with respect \n
to some measure on the indexing collection. The example of set-indexed Lévy \n
processes is considered. The links with function-indexed processes could be \n
discussed.\n
\n
If time permits\, we could also discuss regularity issue : continuity or \n
Hölder regularity.\n
\n
This talk is based on works in collaboration with Ely Merzbach and Alexandre \n
Richard.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2119:field_when:0:79
SUMMARY:Linearly Kleiman groups and double cosets of stabilizers of totally isotropic \n
subspaces of a unitary space.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160522T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160522T140000
URL;VALUE=URI:http://math.biu.ac.il/node/2119
LOCATION:seminar room
DESCRIPTION:Speaker: Nikolai Gordeev\, Russia State Pedagogical University\, St. Petersburg\n
\n
Abstract:\n
Abstract is attached [1].\n
\n
http://math.biu.ac.il/files/math/seminars/gordeev_abstract.pdf\n
\n
[1] http://math.biu.ac.il/files/math/seminars/gordeev_abstract.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2117:field_when:0:80
SUMMARY:One-sided epsilon-approximants
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160529T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160529T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2117
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Gabriel Nivasch (Ariel University)\n
\n
Abstract:\n
We introduce the notion of "one-sided epsilon-approximants"\, which is in \n
strength between epsilon-nets and usual (two-sided) epsilon-approximants. \n
Given an n-point set P in R^d\, a one-sided epsilon-approximant for P (with \n
respect to convex sets) is a multiset A such that\, for every convex set C\, we \n
have |P cap C|/|P| - |A cap C|/|A| <= epsilon.\n
We show that\, in contrast with the usual epsilon-approximants\, every P has a \n
one-sided epsilon-approximant with respect to convex sets of size g(eps\, d) \n
for some g\, but independent of n.\n
Unfortunately\, due to the use of a geometric Ramsey theorem\, our bound is \n
very weak: g(eps\, d) <= 2^2^...^2^(1/epsilon)^c\, with d-1 2's.\n
For more info\, see arXiv:1603.05717\n
Joint work with Boris Bukh.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2116:field_when:0:81
SUMMARY:Improved bounds on the Hadwiger-Debrunner numbers
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160522T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160522T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2116
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Chaya Keller (Ben-Gurion University)\n
\n
Abstract:\n
\n
\n
The classical Helly's theorem states that if in a family of compact convex \n
sets in R^d every d+1 members have a non-empty intersection then the whole \n
family has a non-empty intersection. In an attempt to generalize Helly's \n
theorem\, in 1957 Hadwiger and Debrunner posed a conjecture that was proved \n
more than 30 years later in a celebrated result of Alon and Kleitman: For any \n
p\,q (p >= q > d) there exists a constant C=C(p\,q\,d) such that the following \n
holds: If in a family of compact convex sets\, out of every p members some q \n
intersect\, then the whole family can be pierced with C points. \n
Hadwiger and Debrunner themselves showed that if q is very close to p\, then \n
C=p-q+1 suffices. The proof of Alon and Kleitman yields a huge bound \n
C=O(p^{d^2+d})\, and providing sharp upper bounds on the minimal possible C \n
remains a wide open problem.\n
\n
In this talk we show an improvement of the best known bound on C for all \n
pairs (p\,q). In particular\, for a wide range of values of q\, we reduce C all \n
the way to the almost optimal bound p-q+1<=C<=p-q+2. This is the first near \n
tight estimate of C since the 1957 Hadwiger-Debrunner theorem.\n
\n
Joint work with Shakhar Smorodinsky and Gabor Tardos.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2115:field_when:0:82
SUMMARY:Nonpositive immersions and counting cycles
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160525T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160525T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2115
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Daniel Wise (McGill University and Technion)\n
\n
Abstract:\n
The "nonpositive immersion" property is a condition on a 2-complex X\n
\n
that generalizes being a surface. When X has this property\, its\n
\n
fundamental group appears to have has some very nice properties which\n
\n
I will discuss. I will spend the remainder of the talk outlining a\n
\n
proof that the nonpositive immersion property holds for a 2-complex\n
\n
obtained by attaching a single 2-cell to a graph. This was proven\n
\n
recently with Joseph Helfer and also independently by Lars Louder and Henry \n
Wilton.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2113:field_when:0:83
SUMMARY:Finite volume scheme for a parabolic equation with a non-monotone diffusion \n
function
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160523T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160523T160000
URL;VALUE=URI:http://math.biu.ac.il/node/2113
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Pauline Lafitte-Godillon\, D\'epartement de Math\'ematiques & \n
Laboratoire MICS\, France\n
\n
Abstract:\n
Evans and Portilheiro introduced in 2004 the functional framework that allows \n
to tackle \n
the problem of a forward-backward diffusion equation with a cubic-like \n
diffusion function\, \n
that is classically ill-posed. The key is to consider its ``entropy'' \n
formulation\n
determined by considering the equation as the singular limit of a third-order\n
pseudo-parabolic equation. Obtaining numerical simulations is not easy\, since\n
the ill-posedness related to the negativity of the diffusion coefficient \n
induces\n
severe oscillations. However\, we showed that\, in 1D\, the regularization \n
offered by\n
the basic Euler in time-centered finite differences in space renders a fairly\n
good numerical solution\, except for the fact that the entropy condition is\n
violated. We thus proposed an adapted entropic scheme in 1D. The finite \n
volume framework \n
has since allowed us to prove new properties of the problem.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2112:field_when:0:84
SUMMARY:Hardy spaces and variants of the div-curl lemma
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160509T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160509T154000
URL;VALUE=URI:http://math.biu.ac.il/node/2112
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Galia Dafni\, Concordia University\, Montreal\, Canada\n
\n
Abstract:\n
The theory of real Hardy spaces has been applied to the study of partial\n
differential equations in many different contexts. In the 1990's\, one of \n
main results\n
in this direction was the div-curl lemma of Coifman\, Lions\, Meyer and Semmes. \n
We\n
discuss some variants of this lemma in the context of the local Hardy spaces \n
of Goldberg\,\n
and of weighted Hardy spaces. This is joint work with Der-Chen Chang and \n
Hong Yue.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2111:field_when:0:85
SUMMARY:The Ostaszewski space
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160516T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160516T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2111
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Eran Stein\n
\n
Abstract:\n
We shall present Ostaszewski's construction of a perfectly normal\, \n
hereditarily separable\, first countable\, locally countable\, locally compact\, \n
Hausdorff topological space in which every open set is either countable or \n
co-countable.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2103:field_when:0:86
SUMMARY:Rational polygons: Odd compression ratio and odd plane coverings
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160515T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160515T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2103
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Yuri Rabinovich (University of Haifa)\n
\n
Abstract:\n
We show that for any rational polygon P in the plane\, and any odd-sized \n
collection of translates of P\, the area of the set of points covered by an \n
odd number of these translates is bounded away from 0 by a universal \n
constant depending on P alone. \n
\n
The key ingredient of the proof is a construction of an odd cover of \n
the plane by translates of P. That is\, we establish a family of translates \n
of P covering (almost) every point in the plane a uniformly bounded \n
odd number of times. \n
\n
Joint work with Rom Pinchasi.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2100:field_when:0:87
SUMMARY:The Souslin problem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160515T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160515T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2100
LOCATION:seminar room
DESCRIPTION:Speaker: Assaf Rinot\n
\n
Abstract:\n
Recall that the real line is that unique separable\, dense linear ordering \n
with no endpoints in which every bounded set has a least upper bound.\n
Around the year of 1920\, Souslin asked whether the term *separable* in the \n
above characterization may be weakened to *ccc*. (A linear order is said to \n
be separable if it has a countable dense subset. It is ccc if every \n
pairwise-disjoint family of open intervals is countable.)\n
Amazingly enough\, the resolution of this single problem led to many key \n
discoveries in set theory. Also\, consistent counterexamples to this problem \n
play a prominent role in infinite combinatorics.\n
\n
In this talk\, we shall tell the story of the Souslin problem\, and report on \n
an advance recently obtained after 40 years of waiting.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2109:field_when:0:88
SUMMARY:The Erdos-Dushnik-Miller theorem revisited\, part II
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160509T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160509T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2109
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Roy Shalev\n
\n
Abstract:\n
This is part II of last week's talk [1].\n
\n
\n
[1] http://math.biu.ac.il/node/2099
END:VEVENT
BEGIN:VEVENT
UID:calendar:2108:field_when:0:89
SUMMARY:Idempotents inducing a Z_2 grading on nonassociative algebras and their \n
corresponding involutions.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160508T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160508T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2108
LOCATION:seminar room
DESCRIPTION:Speaker: Yoav Segev (BGU)\n
\n
Abstract:\n
Jordan algebras J of charateristic not 2 sometimes contain\n
a set of idempotents (e^2=e) that generate J such that their adjoint\n
map ad_e: u \mapsto ue (u\in J) has the minimal polynomial\n
x(x-1)(x-1/2)\, and with additional restrictions on products\n
of elements in the eigenspaces of ad_e (for each e).\n
Generalizing these properties (not only of such Jordan\n
algebras) Hall\, Rehren\, Shpectorov (HRS) introduced ``Axial algebras\n
of Jordan type''. In my talk I will present structural results\n
on Axial algebras of Jordan type 1/2 (a case which was not\n
dealt with in HRS)\, I will discuss their idempotents e\, the corresponding\n
``Miyamoto involutions'' \tau(e) and the group that these involutions \n
generate.\n
This is joint work with J. Hall\, S. Shpectorov.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2106:field_when:0:90
SUMMARY:On quaternion algebras split by a given extension and hyperelliptic curves
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160518T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160518T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2106
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Darrell Haile (Indiana University)\n
\n
Abstract:\n
See attached file.\n
\n
http://math.biu.ac.il/files/math/seminars/abstractbarilan.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2099:field_when:0:91
SUMMARY:The Erdos-Dushnik-Miller theorem revisited
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160502T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160502T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2099
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Roy Shalev\n
\n
Abstract:\n
We shall present a recent theorem of Raghavan and Todorcevic [1] that uses a \n
Souslin tree to refute a particular generalization of the \n
Erdos-Dushnik-Miller theorem.\n
\n
\n
[1] http://arxiv.org/abs/1602.07901
END:VEVENT
BEGIN:VEVENT
UID:calendar:2104:field_when:0:92
SUMMARY:Class-preserving automorphisms of groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160504T110000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160504T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2104
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Pradeep Kumar Rai (Bar-Ilan University)\n
\n
Abstract:\n
Let G be a group. An automorphism of G is called class-preserving if it \n
maps each group element to a conjugate of it. The obvious examples of \n
class-preserving automorphisms are inner automorphisms. The first example of \n
a group having non-inner class-preserving automorphisms was given by Burnside \n
in 1913. In this talk we shall present a brief survey of the topic and \n
discuss the nilpotency of the outer class-preserving automorphism group\, i.e. \n
the factor group Aut_c(G) / Inn(G)\, where Aut_c(G) is the group of \n
class-preserving automorphisms of G.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2105:field_when:0:93
SUMMARY:On the flat cohomology of binary norm forms
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160504T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160504T110000
URL;VALUE=URI:http://math.biu.ac.il/node/2105
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Rony Bitan (Université Claude Bernard Lyon I)\n
\n
Abstract:\n
In this talk\, we will interpret some classical results of Gauss in the \n
language of flat cohomology and extend them. Given a quadratic number field \n
k = Q(\sqrt{d}) with narrow class number h_d^+\, let O_d be the orthogonal \n
Z-group of the associated norm form q_k. We will describe the structure of \n
the pointed set H^1_fl(Z\, O_d)\, which classifies quadratic forms isomorphic \n
to q_k in the flat topology\, and express its cardinality via h_d^+ and \n
h_{-d}^+. Furthermore\, if N_d is the connected component of O_d\, we show \n
that any N_d - torsor tensored with itself belongs to the principal genus.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2094:field_when:0:94
SUMMARY:Random knots
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160508T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160508T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2094
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Tahl Nowik (Bar-Ilan University)\n
\n
Abstract:\n
We introduce a new model for random knots and links\, based on the petal \n
projection developed by C. Adams et al. We study the distribution of various \n
invariants of knots and links in this model. We view a knot invariant as a \n
random variable on the set of all petal diagrams with n petals\, and ask for \n
its limiting distribution as n --> infinity. We obtain a formula for the \n
limiting distribution of the linking number of a random two-component link. \n
We obtain formulas for all moments of the two most basic Vassiliev invariants \n
of knots\, which are related to the Conway polynomial and the Jones \n
polynomial. These are the first precise formulas given for the distributions \n
or moments of invariants in any model for random knots and links.\n
\n
Joint work with Chaim Even-Zohar\, Joel Hass\, and Nati Linial.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2093:field_when:0:95
SUMMARY:(k\,l)-suitable digraphs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160501T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160501T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2093
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Rani Hod (Bar-Ilan University)\n
\n
Abstract:\n
We discuss a generalization of k-suitable permutations\, defined in 1950 by \n
Dushnik in the context of the order dimension of the boolean lattice.\n
\n
We relate suitable digraphs to communication settings and prove lower and \n
upper bounds on the cardinality of families of (k\,l)-suitable digraphs.\n
\n
Joint work with Elad Haramaty\, Aaron Potechin and Madhu Sudan.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2047:field_when:0:96
SUMMARY:הוכחות חדשות המלמדות שנקודת העיקר של \n
הרמב"ם מתחילה בשעה 6:00 בערב לפי שעון \n
ירושלים.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160105T151500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160105T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2047
LOCATION:Library
DESCRIPTION:Speaker: פרופ' אריאל כהן\n
\n
Abstract:\n
*להרצאה המצולמת [1]*\n
\n
*למצגת ההרצאה [2] 1*\n
\n
*מצגת ההרצאה 2* [3]\n
\n
\n
[1] https://www.youtube.com/watch?v=W-KxX0fkcf8&\;spfreload=10\n
[2] http://u.math.biu.ac.il/~esheds/ariel_cohen.pdf\n
[3] http://u.math.biu.ac.il/~esheds/barilan1a.pptx
END:VEVENT
BEGIN:VEVENT
UID:calendar:2098:field_when:0:97
SUMMARY:On the Riemann–Hilbert problem for the Beltrami equations in quasidisks
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160411T150500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160411T160500
URL;VALUE=URI:http://math.biu.ac.il/node/2098
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. V. Ryazanov\, Institute of Applied Mathematics and Mechanics\, \n
Ukraine\n
\n
Abstract:\n
For the nondegenerate Beltrami equations in the quasidisks and\, in \n
particular\, in smooth\n
Jordan domains\, we prove the existence of regular solutions of the \n
Riemann–Hilbert problem\n
with coefficients of bounded variation and boundary data that are measurable \n
with respect\n
to the absolute harmonic measure (logarithmic capacity).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2097:field_when:0:98
SUMMARY:On sharp inequalities for orthonormal polynomials along a contour
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160411T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160411T150500
URL;VALUE=URI:http://math.biu.ac.il/node/2097
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. F. Abdullayev\, Mersin University\, Turkey\n
\n
Abstract:\n
For a system of polynomials orthonormal with weight on a curve in the \n
complex plane\,\n
the problem of sharp estimates of these polynomials is of considerable \n
importance.\n
We discuss known conditions and inequalities and present certain refinements \n
of them.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2096:field_when:0:99
SUMMARY:Graphs with no unfriendly partitions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160411T101000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160411T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2096
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Ron Langberg\n
\n
Abstract:\n
We shall present a construction (due to Milner and Shelah) of a very large \n
graph which has no unfriendly 2-partition\, and in which every vertex has \n
infinite degree.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2068:field_when:0:100
SUMMARY:המבנה המתמטי של לוח ס"א ראשים.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160329T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160329T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2068
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: ד"ר ערן רביב\n
\n
Abstract:\n
אחד ההישגים המתמטיים המרשימים ביותר\, \n
ככלי עזר ללוח העברי\, הוא לוח ס"א ראשים\, לוח \n
אשר חובר ע"י יצחק בן אברהם בסוף המאה ה- 12. \n
בהרצאה המוצעת נציג:\n
1. 2 שיטות (דומות אך לא זהות) לבניית \n
הלוח.\n
2. נסביר כיצד לאחר "תיקוני גבולות"\, \n
הנובעים מפונקציית מולד תשרי של ראש מחזור\, \n
הלוח מגלם בתוכו את מחזוריות המולדות בלוח \n
העברי (689472 שנים).\n
3. נדגים כיצד ניתן לחשב מתוך לוח זה \n
"שכיחות" של תתי סדרות של רצפים של סימני \n
שנים.\n
4. נציג את נוסחת יפה\, נוכיח אותה ונראה \n
(לראשונה!) דרך לחשב מתוך לוח ס"א ראשים את \n
החסם העליון לנכונות הנוסחה\, ולבסוף נציג \n
גרסה מתוקנת לנוסחה זו\, הנובעת ממסקנת \n
החישוב. \n
\n
קבצים מצורפים:\n
\n
ההרצאה המצולמת [1]\n
\n
מצגת ההרצאה [2]\n
\n
לוח סא תמסיר 1 [3]\n
\n
לוח סא תמסיר 2 [4]\n
\n
תמסיר להרצאה [5]\n
\n
\n
\n
\n
[1] https://www.youtube.com/watch?v=_M7l1J-BE5A\n
[2] http://u.math.biu.ac.il/~esheds/ppt_eran_raviv.pptx\n
[3] http://u.math.biu.ac.il/~esheds/tamsir_board1.pdf\n
[4] http://u.math.biu.ac.il/~esheds/tamsir_board2.pdf\n
[5] http://u.math.biu.ac.il/~esheds/lecture_ tamsir.docx
END:VEVENT
BEGIN:VEVENT
UID:calendar:2082:field_when:0:101
SUMMARY:Uncertainty principle in the hypercube and short vectors in linear codes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160410T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160410T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2082
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Alex Samorodnitsky (Hebrew University\, Jerusalem)\n
\n
Abstract:\n
The uncertainty principle in the n-dimensional hypercube states that if a \n
non-zero function is supported in A and its Fourier transform is supported in \n
B\, then |A||B| is at least 2^n. \n
\n
We consider a relaxed version\, requiring only a non-negligible fraction of \n
the l_2 norm of the function to be attained in A and of its transform in B. \n
Provided either A or B is a Hamming ball\, we give a description of the \n
possible joint behavior of |A| and |B|. This description is tight on the \n
exponential scale (that is\, assuming both A and B are exponentially small). \n
The main technical tool we use is a stronger version of the hypercontractive \n
inequality for functions with exponentially small support. \n
\n
As a corollary we show that any binary linear code contains "many" (in the \n
appropriate sense) codewords whose length is close to that guaranteed by the \n
linear programming bound.\n
\n
Joint work with Yury Polyanskiy.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2092:field_when:0:102
SUMMARY:Mod-p representations of p-adic metaplectic groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160406T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160406T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2092
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Laura Peskin (Weizmann Institute of Science)\n
\n
Abstract:\n
Let F be a p-adic field. The irreducible admissible mod-p representations of \n
a connected reductive group over F have recently been classified up to \n
supercuspidals by Abe-Henniart-Herzig-Vigneras\, building on a method \n
introduced by Herzig in 2011. Their classification is part of an effort to \n
formulate mod-p local Langlands correspondences. The complex representations \n
of certain nonlinear covers of p-adic reductive groups play an interesting \n
role in the classical LLC\, and it is natural to ask whether this is also true \n
in the mod-p setting. As a first step\, I’ll explain how to modify \n
Herzig’s method in order to classify irreducible admissible genuine mod-p \n
representations of the metaplectic double cover of Sp_{2n}(F). The main \n
consequence of the classification is that parabolically induced genuine mod-p \n
representations are irreducible in the metaplectic case more often than in \n
the reductive case\; in particular\, all parabolically induced genuine \n
representations of the metaplectic cover of SL_{2}(F) are irreducible. This \n
is joint work with Karol Koziol.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2090:field_when:0:103
SUMMARY:Local and global colorability of graphs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160403T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160403T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2090
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Omri Ben Eliezer ׂ(Tel-Aviv University)\n
\n
Abstract:\n
It is shown that for any fixed c \geq 3 and r\, the maximum \n
possible chromatic number of a graph on n vertices in which every \n
subgraph of radius at most r is c-colorable is n^(1/r+1) up to \n
a multiplicative factor logarithmic in n: in fact\, it is O((n/log(n)) ^ \n
(1/r+1)) and Omega(n^(1/r+1) / log(n)). \n
\n
The proof is based on a careful analysis of the local and global \n
colorability of random graphs and implies\, in particular\, that a random \n
n-vertex graph with the right edge probability has typically a chromatic \n
number as above and yet most balls of radius r in it are 2-degenerate.\n
\n
Joint work with Noga Alon.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2091:field_when:0:104
SUMMARY:Mixing\, coloring and expansion of Ramanujan complexes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160320T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160320T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2091
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Konstantin Golubev (Hebrew University\, Jerusalem)\n
\n
Abstract:\n
Ramanujan graphs\, constructed by Lubotzky\, Phillips and Sarnak and known \n
also as the LPS graphs\, are certain quotients of the Bruhat-Tits building of \n
PGL_2(Q_p). These graphs form a family of expander graphs\, and serve as \n
an explicit construction of graphs of high girth and large chromatic \n
number. High dimensional counterparts of the LPS graphs are the \n
Ramanujan Complexes\, constructed by Lubotzky\, Samuels and Vishne\, as \n
quotients of the Bruhat-Tits building of PGL_d over a non-archimedean field \n
of finite characteristic. I'll talk about the mixing of these complexes\, \n
which implies that they have good expansion and large chromatic number. \n
\n
If time permits\, I'll talk about analogous results for general hypergraphs \n
satisfying certain regularity condition. \n
\n
Joint work with S.Evra\, A.Lubotzky.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2088:field_when:0:105
SUMMARY:From Hrushovski counterexamples to Grothendieck period conjecture
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160327T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160327T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2088
LOCATION:seminar room
DESCRIPTION:Speaker: Boris Zilber (Oxford)\n
\n
Abstract: In 1988 Hrushovski found counterexamples to the speaker's \n
conjectures that categorical theories are in a certain sense reducible to \n
algebraic geometry. Actually\, the counterexamples are the outcomes of a \n
very special abstract construction which is based on a combinatorial \n
inequality in terms of dimensions of algebraic origin. The counterexamples \n
were originally perceived as unwelcome mathematical pathologies. We will \n
explain how Hrushovski's construction can be linked to the theory of \n
classical transcendental functions and how it leads to certain conjectures \n
which eventually can be recognised as a form of Grothendieck - Andre period \n
conjecture.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2074:field_when:0:106
SUMMARY:A Dowker space from a ladder system
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160404T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160404T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2074
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Shahak Shama\n
\n
Abstract:\n
We shall show that any ladder system on w1 induces a certain uncountable \n
topological space\, and then present sufficient conditions on the ladder \n
system that makes the corresponding space into a Dowker space [1].\n
\n
\n
[1] https://en.wikipedia.org/wiki/Dowker_space
END:VEVENT
BEGIN:VEVENT
UID:calendar:2086:field_when:0:107
SUMMARY:Increase of collision probability by flow delay
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160327T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160327T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2086
LOCATION:Building 216 Room 201
DESCRIPTION:Speaker: Itzhak Fouxon - Hebrew University\n
\n
Abstract:\n
We consider motion of inertial particles in random (turbulent) flow. Inertia \n
of particles causes delay:\n
the particle's velocity is not the local flow but the flow at the \n
trajectory some time ago. We demonstrate that this causes particles' \n
clustering on fractal set. This has uses in rain prediction problem and \n
industry.\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2085:field_when:0:108
SUMMARY:On the Fourier transform of a function of several variables
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160328T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160328T154000
URL;VALUE=URI:http://math.biu.ac.il/node/2085
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. R. Trigub\n
\n
Abstract:\n
For functions $f(x_{1}\,x_{2})=f_{0}\ig(\max\{|x_{1}|\,|x_{2}|\}\ig)$ from\n
$L_{1}(\mathbb{R}^{2})$\, sufficient and necessary conditions for the \n
belonging of their Fourier transform\n
$\widehat{f}$ to $L_{1}(\mathbb{R}^{2})$ as well as of a function $t\cdot \n
\sup\limits_{y_{1}^{2}+y_{2}^{2}\geq\n
t^{2}}\ig|\widehat{f}(y_{1}\,y_{2})\ig|$ to $L_{1}(\mathbb{R}^{1}_{+})$. As \n
for the positivity of $\widehat{f}$ on\n
$\mathbb{R}^{2}$\, it is completely reduced to the same question on \n
$\mathbb{R}^{1}$ for a function\n
$f_{1}(x)=|x|f_{0}\ig(|x|\ig)+\int\limits_{|x|}^{\infty}f_{0}(t)dt$.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2081:field_when:0:109
SUMMARY:Every property of outerplanar graphs is testable in O(poly(\log n)) queries
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160327T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160327T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2081
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Ilan Newman (University of Haifa)\n
\n
Abstract:\n
For a graph on $n$ vertices\, and an integer $D$\, let the $D$-local view of \n
$G=(V\,E)$ be the collection (multiset) of the unlabelled $n$ balls of \n
distance $D$ around the vertices.\n
\n
The main question that motivates this study is: what can be said about $G$ \n
knowing only its $D$-local view for some constant $D$.\n
\n
For constant bounded degree planar (or more generally hyperfinite) graphs\, \n
Newman-Sohler [2011] following a long sequence of work\, show that for any \n
$\epsilon > 0$\, there is a $D$ such that the $D$-local view of the graph \n
determines the graph up to the deletion / insertion of at most $\epsilon n$ \n
edges. This in turn\, implies that every property of planar (hyperfinite) \n
graphs can be tested (in the sense of property testing\, by constantly many \n
queries.\n
\n
What happens in non-bounded degree planar graphs? The answer is currently \n
still open. However\, we show\, following Yoshida's results on forests\, that \n
the above phenomenon still holds for outerplanar graphs. The implication to \n
testing is deteriorated\, though. Testing now requires $O(poly(\log n))$ \n
queries.\n
\n
I will describe the ideas behind the two results\, the later which is a joint \n
work with Jasine Babu and Areej Khoury.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2084:field_when:0:110
SUMMARY:Deligne categories and the limit of categories Rep(GL(m|n))
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160330T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160330T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2084
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Inna Entova Aizenbud (Hebrew University of Jerusalem)\n
\n
Abstract:\n
Deligne categories Rep(GL_t) (for a complex parameter t) have been \n
constructed by Deligne and Milne in 1982 as a polynomial extrapolation of the \n
categories of algebraic representations of the general \n
linear groups GL_n(C). \n
In this talk\, we will show how to construct a "free abelian tensor category \n
generated by one object of dimension t"\, which will be\, in a sense\, the \n
smallest abelian tensor category which contains the respective Deligne's \n
category Rep(GL_t). \n
The construction is based on an interesting stabilization phenomenon \n
occurring in categories of representations of supergroups GL(m|n) when t is \n
an integer and m-n=t. \n
This is based on a joint work with V. Seganova and V. Hinich.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2061:field_when:0:111
SUMMARY:Infinite trees and partition relations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160307T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160307T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2061
LOCATION:building #502\, room #9
DESCRIPTION:Speaker: Dani Livne\n
\n
Abstract:\n
Infinite trees and partition calculus (aka\, Ramsey theory) are well-known to \n
be intertwined. For instance\, Ramsey theorem implies Konig's lemma that \n
asserts that every infinite tree which is finitely branching has an infinite \n
path.\n
In this talk\, we shall deal with uncountable trees such as Souslin trees and \n
Aronszajn trees\, and show how to derive negative partition relations from \n
them.\n
\n
\n
Lecture notes. [1]\n
\n
\n
[1] http://blog.assafrinot.com/?p=4070
END:VEVENT
BEGIN:VEVENT
UID:calendar:2075:field_when:0:112
SUMMARY:Selected topics for the weak topology of Banach spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160320T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160320T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2075
LOCATION:Seminar Room
DESCRIPTION:Speaker: Prof. Jerzy Kąkol\n
\n
Abstract:\n
Corson (1961) started a systematic study of certaintopological properties of \n
the weak topology w of Banach spaces E. This\n
line of research provided more general classes such as reflexive\n
Banach spaces\, Weakly Compactly Generated Banach spaces and the class\n
of weakly K-analytic and weakly K-countably determined Banach spaces.\n
On the other hand\, various topological properties generalizing\n
metrizability have been studied intensively by topologists and\n
analysts. Let us mention\, for example\, the first countability\,\n
Frechet-Urysohn property\, sequentiality\, k-space property\, and\n
countable tightness. Each property (apart the countable tightness)\n
forces a Banach space E to be finite-dimensional\, whenever E with the\n
weak topology w is assumed to be a space of the above type. This is a\n
simple consequence of a theorem of Schluchtermann and Wheeler that an\n
infinite-dimensional Banach space is never a k-space in the weak\n
topology. These results show also that the question when a Banach\n
space endowed with the weak topology is homeomorphic to a certain\n
fixed model space from the infinite-dimensional topology is very\n
restrictive and motivated specialists to detect the above properties\n
only for some natural classes of subsets of E\, e.g.\, balls or bounded\n
subsets of E. We collect some classical and recent results of this\n
type\, and characterize those Banach spaces E whose unit ball B_w is\n
k_R-space or even has the Ascoli property. Some basic concepts from\n
probability theory and measure theoretic properties of the space l_1\n
will be used.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2072:field_when:0:113
SUMMARY:How to construct a Souslin tree\, lecture #2
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160321T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160321T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2072
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Ari Brodsky (BIU)\n
\n
Abstract:\n
We shall describe a construction of a Souslin tree\, following our recent \n
paper [1].\n
\n
\n
[1] http://blog.assafrinot.com/?p=4059
END:VEVENT
BEGIN:VEVENT
UID:calendar:2071:field_when:0:114
SUMMARY:Comparing the degrees of unconstrained and constrained approximation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160321T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160321T155500
URL;VALUE=URI:http://math.biu.ac.il/node/2071
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. D. Leviatan\, Tel-Aviv University\n
\n
Abstract:\n
It is quite obvious that one should expect that the degree of constrained \n
approximation\n
be worse than the degree of unconstrained approximation. However\, it turns \n
out that in certain cases\n
we can deduce the behavior of the degrees of the former from information \n
about the latter.\n
\n
Let $E_n(f)$ denote the degree of approximation of $f\in C[-1\,1]$\,\n
by algebraic polynomials of degree $ that for some $\alpha>0$ and $\Cal \n
N\ge1$\,\n
$$n^\alpha E_n(f)\leq1\,\quad n\geq\Cal N.$$\n
Suppose that $f\in C[-1\,1]$\, changes its monotonicity or convexity $s\ge0$ \n
times in $[-1\,1]$ ($s=0$ means that $f$\n
is monotone or convex\, respectively). We are interested in what may be said \n
about its degree of\n
approximation by polynomials of degree $ $f$. Specifically\, if $f$ changes \n
its monotonicity or convexity at\n
$Y_s:=\{y_1\,\dots\,y_s\}$ ($Y_0=\emptyset$) and the degrees of comonotone and \n
coconvex approximation\n
are denoted by $E^{(q)}_n(f\,Y_s)$\, $q=1\,2$\, respectively. We investigate when \n
can one say that\n
$$n^\alpha E^{(q)}_n(f\,Y_s)\le c(\alpha\,s\,\Cal N)\,\quad n\ge\Cal N^*\,$$\n
for some $\Cal N^*$. Clearly\, $\Cal N^*$\, if it exists at all (we prove it\n
always does)\, depends on $\alpha$\, $s$ and $\Cal N$. However\, it turns\n
out that for certain values of $\alpha$\, $s$ and $\Cal N$\, $\Cal N^*$ depends \n
also\n
on $Y_s$\, and in some cases even on $f$ itself\, and this dependence is \n
essential.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2070:field_when:0:115
SUMMARY:Mappings with integrally controlled $p$-moduli
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160314T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160314T160000
URL;VALUE=URI:http://math.biu.ac.il/node/2070
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. A. Golberg\, Holon Institute of Technology\n
\n
Abstract: We consider classes of mappings (with controlled moduli) whose \n
$p$-module of the families of curves/surfaces is restricted by integrals \n
containing measurable functions and arbitrary admissible metrics. In the talk \n
we discuss various properties of mappings with controlled moduli including \n
their differential features (Lusin's $N-$ and $N^{-1}$-conditions\, Jacobian \n
bounds\, estimates for distortion dilatations\, H\"older/logarithmically \n
H\"older continuity) and the topological structure (openness\, discreteness\, \n
invertibility\, finiteness of the multiplicity function). This allows us to \n
investigate the interconnection between mappings of bounded and finite \n
distortion defined analytically and mapping with controlled moduli having no \n
analytic assumptions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2053:field_when:0:116
SUMMARY:הלוח העברי לפי התפיסה היהודית הקראית \n
המבוסס על הידע האסטרונומי העדכני.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160301T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160301T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2053
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: ר' שמואל מגדי הלוי\n
\n
Abstract:\n
קידוש החודש הינה מצווה שעליה תלויות הרבה \n
מצוות אחרות.\n
\n
מהם היסודות לקיום המצוות לפי ההלכה \n
היהודית הקראית?\n
מה מיחד את הלוח העברי לפי התפיסה היהודית \n
הקראית?\n
מהם המקורות המקראיים לידיעת המצב לקידוש \n
החודש?\n
הסבר אסטרונומי כללי להבנת מסלולו צורתו של \n
הירח ומחזוריותו.\n
מהו המצב האסטרונוי לקידוש החודש?\n
הקריטריונים האסטרונומיים לקידוש החודש.\n
הצגת ריכוזי ניתונים אסטרונומיים לקביעת \n
לוח.\n
הצגת דוגמאות.\n
\n
*להרצאה המצולמת [1]*\n
\n
\n
\n
\n
\n
\n
\n
\n
[1] https://www.youtube.com/watch?v=HMtx1_Rx5DI&\;spfreload=10
END:VEVENT
BEGIN:VEVENT
UID:calendar:2067:field_when:0:117
SUMMARY:Detecting sphere boundaries of hyperbolic groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160316T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160316T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2067
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Benjamin Beeker (Hebrew University of Jerusalem)\n
\n
Abstract: We show that the boundary of a one-ended hyperbolic group that has \n
enough codimension-1 surface subgroups and is simply connected at infinity is \n
homeomorphic to a 2-sphere. Together with a result of Markovic\, it follows \n
that these groups are Kleinian groups. In my talk\, I will describe this \n
result and give a sketch of the proof. This is joint work with N. \n
Lazarovich.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2063:field_when:0:118
SUMMARY:Same Graph\, Different Universe
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160313T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160313T153000
URL;VALUE=URI:http://math.biu.ac.il/node/2063
LOCATION:Math building\, 3rd floor seminar room (216/201)
DESCRIPTION:Speaker: Assaf Rinot (Bar-Ilan University)\n
\n
Abstract:\n
May the same graph admit two different chromatic numbers in two different \n
universes? how about infinitely many different values? and can this be \n
achieved without changing the cardinals structure?\n
\n
In this talk\, we shall give various examples of graphs+universes that address \n
the above questions.\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2056:field_when:0:119
SUMMARY:Improvisations on the Hall marriage theorem: Completing Latin squares and \n
Sudokus
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160306T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160306T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2056
LOCATION:Department room
DESCRIPTION:Speaker: Eli Shamir (Hebrew University\, Jerusalem)\n
\n
Abstract:\n
The key concept of our discussion is that of a perfect matching (PM) in a \n
bipartite graph. The expansion condition in Hall's marriage theorem can \n
be extended to an unbiased 2-sided one. This enables an alternative (and \n
simpler) proof of Evans' (proven) Conjecture:\n
A partial nxn Latin square with n-1 dictated entries admits a completion to \n
a full Latin square. \n
PMs are used to successively fill the square by rows\, columns or \n
diagonals. Latin square tables correspond to quasi-groups\; the ones \n
corresponding to groups are only a tiny fraction of them\, as n \n
grows. However\, for Sudoku tables of order mnxmn\, the completion (say by \n
diagonals) usually fails\, even if there are no dictated entries\, unless \n
they are conjugates of a twisted product of two groups\, of orders n and m.\n
\n
An open problem for sudoku lovers: Is there a sudoku square (of any order) \n
which is not a conjugate of a twisted product of groups?\n
\n
No prior knowledge needed.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:2065:field_when:0:120
SUMMARY:Pro-isomorphic zeta functions and p-adic integrals
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160313T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160313T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2065
LOCATION:seminar room
DESCRIPTION:Speaker: Dr. M. Schein\, (Bar Ilan)\n
\n
Abstract:\n
A finitely generated group $G$ has only a finite number\, say $a_n(G)$\, of \n
subgroups of any given index $n$. The study of subgroup growth\, i.e. of the \n
behavior of this sequence\, has been an active area of research for several \n
decades. A variant problem investigates the sequence $a_n^\wedge (G)$ \n
counting subgroups of index $n$ whose profinite completion is isomorphic to \n
that of the original group $G$\, and in particular the analytic properties of \n
the Dirichlet series derived from this sequence.\n
\n
\n
\n
The computation of these Dirichlet series turns out to be equivalent to \n
the computation of some p-adic integrals over algebraic groups\; integrals of \n
this type have been studied extensively since the 1960's. Each of these two \n
ways of approaching what turns out to be the same problem sheds light on the \n
other. The talk will discuss the connection between pro-isomorphic \n
subgroups and p-adic integrals. It will also discuss recent joint work with \n
Mark Berman on the behavior of pro-isomorphic zeta functions under base \n
extension. No knowledge of the subject will be assumed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2064:field_when:0:121
SUMMARY:How to construct a Souslin tree the right way
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160314T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160314T120000
URL;VALUE=URI:http://math.biu.ac.il/node/2064
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Ari Brodsky (BIU)\n
\n
Abstract:\n
We shall describe a construction of a Souslin tree\, following our recent \n
paper [1].\n
\n
\n
\n
[1] http://blog.assafrinot.com/?p=4059
END:VEVENT
BEGIN:VEVENT
UID:calendar:2057:field_when:0:122
SUMMARY:Improvisations on the Hall marriage theorem: Completing Latin squares and \n
Sudokus
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160306T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160306T130000
URL;VALUE=URI:http://math.biu.ac.il/node/2057
LOCATION:seminar room
DESCRIPTION:Speaker: Prof. Eli Shamir\, Hebrew University\, Jerusalem\n
\n
Abstract: The key concept of our discussion is that of a perfect matching \n
(PM) in a bipartite graph.\n
The expansion condition in Hall's marriage theorem can be extended to an \n
unbiased 2-sided one.\n
This enables an alternative (and simpler) proof of Evans' (proven) \n
Conjecture:\n
A partial nxn Latin square with n-1 dictated entries admits a completion to \n
a full Latin square. \n
PMs are used to successively fill the square by rows\, columns or \n
diagonals. Latin square tables correspond to quasi-groups\; the ones \n
corresponding to groups are only a tiny fraction of them\, as n \n
grows. However\, for Sudoku tables of order mnxmn\, the completion (say by \n
diagonals) usually fails\, even if there are no dictated entries\, unless \n
they are conjugates of a twisted product of two groups\, of orders n and m.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2054:field_when:0:123
SUMMARY:A noncommutative Matlis-Greenlees-May equivalence
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160309T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160309T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2054
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Rishi Vyas (Ben-Gurion University)\n
\n
Abstract: The notion of a weakly proregular sequence in a commutative ring \n
was first formally introduced by Alonso-Jeremias-Lipman (though the property \n
that it formalizes was already known to Grothendieck)\, and further studied by \n
Schenzel\, and Porta-Shaul-Yekutieli. \n
Roughly speaking\, an element s in a commutative ring A is said to be \n
weakly proregular if every module over A can be reconstructed from its \n
localisation at s considered along with its local cohomology at the ideal \n
generated by s. This notion extends naturally to finite sequences of \n
elements: a precise definition will be given during the talk. An ideal in a \n
commutative ring is called weakly proregular if it has a weakly proregular \n
generating set. Every ideal in a commutative noetherian ring is weakly \n
proregular.\n
It turns out that weak proregularity is the appropriate context for the \n
Matlis-Greenlees-May (MGM) equivalence: given a weakly proregular ideal I in \n
a commutative ring A\, there is an equivalence of triangulated categories \n
(given in one direction by derived local cohomology and in the other by \n
derived completion at I) between cohomologically I-torsion (i.e. complexes \n
with I-torsion cohomology) and cohomologically I-complete complexes in the \n
derived category of A.\n
\n
In this talk\, we will give a categorical characterization of weak \n
proregularity: this characterization then serves as the foundation for a \n
noncommutative generalisation of this notion. As a consequence\, we \n
will arrive at a noncommutative variant of the MGM equivalence. This work \n
is joint with Amnon Yekutieli.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2051:field_when:0:124
SUMMARY:On the reduction of Galois representations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160302T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160302T113000
URL;VALUE=URI:http://math.biu.ac.il/node/2051
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Shalini Bhattacharya (Bar-Ilan University)\n
\n
Abstract:\n
I will describe the problem of mod p reduction of p-adic Galois \n
representations. For crystalline representations\, the reduction can be \n
computed using the compatibility of p-adic and mod p Local Langlands \n
Correspondences\; this method was first introduced by Breuil in 2003. After \n
giving a brief sketch of the history of the problem\, I will discuss how the \n
reductions behave for representations with slopes in the half-open interval \n
[1\,2). This is based on joint works with Eknath Ghate\, and also with Sandra \n
Rozensztajn for slope 1.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2044:field_when:0:125
SUMMARY:יום טוב שני של גלויות בתקופת חז"ל
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151020T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151020T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2044
LOCATION:Library
DESCRIPTION:Speaker: הרב ד"ר שי ואלטר\n
\n
Abstract:\n
*להרצאה המצולמת [1]*\n
\n
\n
[1] https://www.youtube.com/watch?v=9Exk8xQbybY&\;spfreload=10
END:VEVENT
BEGIN:VEVENT
UID:calendar:1921:field_when:0:126
SUMMARY:'מחלוקת רס"ג ובן מאיר' ו- 'עיגול דרב נחשון \n
גאון' - ניתוח ממצאים מהגניזה הקהירית.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151110T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151110T183000
URL;VALUE=URI:http://math.biu.ac.il/node/1921
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: ד"ר ערן רביב\n
\n
Abstract:\n
בהרצאה המוצעת נציג כמה מסמכים מהגניזה \n
המכילים טבלאות של שנים.\n
\n
עד כה טבלאות אלו לא נותחו ונחקרו על ידי \n
חוקרי הלוח העברי\, משום שנראו כזניחות ואולי \n
משום שלא הבינו את פשרן והם היו כספר החתום.\n
בהרצאה נציג את הרקע הנדרש לנדון ונסביר את \n
אופן פענוח סימני השנה המופיעים בטבלאות \n
אלו.\n
המסקנה שלכאורה עולה מאחד המסמכים מרעישה \n
ומפתיעה כאחד– אנו מוצאים\, לכאורה\, עדות על \n
קיום מסורת של סימן השנה כשיטת בן מאיר\, וזאת \n
כ- 184 שנים לפני פרוץ המחלוקת המפורסמת בין \n
רס"ג לבין בן מאיר בר פלוגתו.\n
בהרצאה נפריך מסקנה זו ונסביר כיצד הגיעו \n
לסימני השנה המופיעים בטבלאות אלו.\n
\n
\n
*להרצאה המצולמת* [1] \n
\n
*ל* [2]*מצגת ההרצאה [3]*\n
\n
\n
[1] http://www.youtube.com/watch?v=VsPbpTI17-o&\;spfreload=10\n
[2] http://www.youtube.com/watch?v=VsPbpTI17-o&\;spfreload=10\n
[3] http://u.math.biu.ac.il/~esheds/eranraviv.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2046:field_when:0:127
SUMMARY:ניסיון בן מאיר לאמץ את מולדות אל-בתאני \n
החדשים (בזמנו) במקום אלה הישנים של תלמי.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151215T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151215T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2046
LOCATION:Library
DESCRIPTION:Speaker: אינג' ר' יעקב לוינגר\n
\n
Abstract:\n
*להרצאה המצולמת [1]*\n
\n
*למצגת ההרצאה* [2]\n
\n
\n
[1] https://www.youtube.com/watch?v=cn0lNCMPsKA\n
[2] http://u.math.biu.ac.il/~esheds/levinger_15_12_15.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2048:field_when:0:128
SUMMARY:כ- 1500 שנה של לוח קבוע בזכות טבלה אחת.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160119T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160119T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2048
LOCATION:Library
DESCRIPTION:Speaker: עו"ד ישראל סלומון\n
\n
Abstract:\n
*להרצאה המצולמת [1]*\n
\n
*למצגת ההרצאה [2]*\n
\n
\n
[1] https://www.youtube.com/watch?v=hyawNLQUSzM&\;spfreload=10\n
[2] http://u.math.biu.ac.il/~esheds/israel_solomon.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:2045:field_when:0:129
SUMMARY:מבט חדש על מוצא 'מולד העיקר' (בהר''ד/וי''ד) של \n
הלוח העברי\, ממולדות תלמי ב'אלמגסט'
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151124T171500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151124T183000
URL;VALUE=URI:http://math.biu.ac.il/node/2045
LOCATION:Library
DESCRIPTION:Speaker: אינג' ר' יעקב לוינגר\n
\n
Abstract:\n
*להרצאה המצולמת [1]*\n
\n
*למצגת ההרצאה* [2]\n
\n
\n
[1] https://www.youtube.com/watch?v=DDvF6IFo02M\n
[2] http://u.math.biu.ac.il/~esheds/levinger.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:1985:field_when:0:130
SUMMARY:The Galvin-Hajnal formula and its applications to Cardinal Arithmetic
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160229T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160229T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1985
LOCATION:Building 502\, Room 9
DESCRIPTION:Speaker: Luis Pereira (Lisbon)\n
\n
Abstract:\n
The purpose of this talk is to present the main developments in Cardinal \n
Arithmetic from 1960 to 1975. After a brief review of the basic independence \n
results\, we will review the basic definitions and results about ultrapowers \n
and measurable cardinals and proceed to Scott's and Vopenka's results in \n
Cardinal Arithmetic regarding measurable cardinals and singular cardinals of \n
measurable cofinality. These results are generalizable to all singular \n
cardinals of uncountable cofinality and this is what we will look at next. \n
For that will start with the basic definitions and examples regarding the \n
Galvin-Hajnal norm and finish with the application of the Galvin-Hajnal bound \n
for families of almost disjoint functions to Cardinal Arithmetic.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1984:field_when:0:131
SUMMARY:Universal Dynamics of Human Microbial Ecosystems
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160119T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160119T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1984
LOCATION:Math seminar room - building 216\, room 201
DESCRIPTION:Speaker: Dr. Amir Bashan - Harvard Medical School\n
\n
Abstract:\n
\n
\n
Our body is colonized by trillions of microbes\, known as the human \n
microbiome\, living with us in a complex ecological system. Those \n
micro-organisms play a crucial role in determining our health and well-being\, \n
and there are ongoing efforts to develop tools and strategies to control \n
these ecosystems. In this talk I address a simple but fundamental question: \n
are the microbial ecosystems in different people governed by the same \n
host-independent ecological principles\, represented by \n
a characteristic (i.e. universal) mathematical model? Answering this \n
question determines the feasibility of general therapies and control \n
strategies for the human microbiome. I will introduce our novel methodology \n
that distinguishes between two scenarios: host-independent and host-specific \n
underlying dynamics. This methodology has been applied to study different \n
body sites across healthy subjects. We also analyzed the gut microbial \n
dynamics of subjects with recurrent Clostridium difficile infection (rCDI) \n
and the same set of subjects after fecal microbiota transplantation (FMT). \n
The results can fundamentally improve our understanding of forces and \n
processes shaping human microbial ecosystems\, paving the way to design \n
general microbiome-based therapies.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1918:field_when:0:132
SUMMARY:Normally Regular Digraphs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160117T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160117T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1918
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Leif Jørgensen (Aalborg U\, Denmark)\n
\n
Abstract:\n
A normally regular digraph with parameters (v\,k\,λ\,μ) is a directed graph \n
with adjacency matrix A satisfying the equation AAT=kI+λ(A+AT) \n
+μ(J-I-A-AT). I.e.\, the number of common out-neighbours of vertices x and \n
y is k if x=y\, μ if x and y are non-adjacent\, λ if x and y are adjacent in \n
one direction and 2λ-μ if they are adjacent in both directions.\n
The adjacency matrix of a normally regular graph is normal\, and all \n
eigenvalues other than k are on one circle in the complex plane. This \n
property characterizes normally regular digraphs.\n
We consider constructions and structural characterizations and we also \n
consider connections to association schemes\, symmetric 2-designs\, generalized \n
difference sets\, and partition of a projective plane into subplanes.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1982:field_when:0:133
SUMMARY:Integral formulae for codimension-one foliated Finsler spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160118T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160118T160000
URL;VALUE=URI:http://math.biu.ac.il/node/1982
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Vladimir Rovenski\, University of Haifa\n
\n
Abstract:\n
Recent decades brought increasing interest in Finsler spaces $(M\,F)$\,\n
especially\, in extrinsic geometry of their hypersurfaces.\n
Randers metrics (i.e.\, $F=\alpha+\eta$\, $\alpha$ being the norm of a \n
Riemannian structure\n
and $\eta$ a 1-form of $\alpha$-norm smaller than $1$ on~$M$)\,\n
appeared in Zermelo's control problem\, are of special interest.\n
\n
After a short survey of above\, we will discuss\n
Integral formulae\, which provide obstructions for existence of foliations\n
(or compact leaves of them) with given geometric properties.\n
The first known Integral formula (by G.\\,Reeb) for codimension-1 foliated \n
closed manifolds tells us that\n
the total mean curvature $H$ of the leaves is zero (thus\, either $H\equiv0$ \n
or $H(x)H(y)<0$ for some $x\,y\in M$).\n
\n
Using a unit normal to the leaves of a codimension-one foliated $(M\,F)$\,\n
we define a new Riemannian metric $g$ on $M$\, which for Randers case depends \n
nicely on $(\alpha\,\eta)$.\n
For that $g$ we derive several geometric invariants of a foliation in terms \n
of $F$\;\n
then express them in terms of invariants of $\alpha$ and~$\eta$.\n
Using our results \cite{rw2} for Riemannian case\, we present new Integral \n
formulae\n
for codimension-one foliated $(M\, F)$ and $(M\, \alpha+\eta)$.\n
Some of them generalize Reeb's formula.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1917:field_when:0:134
SUMMARY:Non-crossing partitions and a diameter problem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160110T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160110T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1917
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Ron Adin (BIU)\n
\n
Abstract: The maximal chains in the non-crossing partition lattice have a \n
natural graph structure.\n
The (still open) problem of determining the diameter of this graph is a \n
trigger for an exciting tour through\n
reduced words of a Coxeter element in the symmetric group\, a 0-Hecke \n
algebra action\, a special EL-labeling\, q\,t-Catalan numbers\, and non-crossing \n
alternating trees. We shall describe connections\, results and open \n
problems in this context.\n
Joint work with Yuval Roichman.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1979:field_when:0:135
SUMMARY:Geometric degree estimate for a Jacobian mapping of a plane via algebraic \n
degrees.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160103T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160103T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1979
LOCATION:seminar room
DESCRIPTION:Speaker: Leonid Makar -Limanov\n
\n
Abstract: Yitang Zhang who became famous recently thanks to brake-through in \n
the twins conjecture wrote his PhD thesis on the plane Jacobian conjecture \n
where he gave an estimate of the geometric degree of the corresponding \n
mapping of a plane via algebraic degrees of the images of the coordinate \n
functions. In my talk I'll explain how to gets a better estimate via the \n
Newton polytope approach.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1978:field_when:0:136
SUMMARY:Diffraction theory for aperiodic point sets in Lie groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160104T143000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160104T160000
URL;VALUE=URI:http://math.biu.ac.il/node/1978
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Tobias Hartnick\, Technion\n
\n
Abstract:\n
The study of aperiodic point sets in Euclidean space is a classical topic in \n
harmonic analysis\, \n
combinatorics and geometry. Aperiodic point sets in R^3 are models for \n
quasi-crystals\, and in \n
this context it is of interest to study their diffraction measure\, i.e. the \n
way they scatter an \n
incoming laser or x-ray beam. By a classical theorem of Meyer\, every \n
sufficiently regular \n
aperiodic point set in a Euclidean space is a shadow of a periodic one in a \n
larger locally \n
compact abelian group. The diffraction of these "model sets" can be computed \n
in terms of a \n
certain group of irrational rotations of an associated torus.\n
\n
In this talk\, I will review the classical theory of diffraction of Euclidean \n
model sets and then \n
explain how the theory generalizes to model sets in arbitrary (non-abelian) \n
locally compact groups. \n
We will explain the construction of new examples of different flavours\, and \n
how the classical \n
theory has to be modified in order to accomodate these new examples. We will \n
focus on the case \n
of model sets in groups admitting a Gelfand pair\, since for these the \n
(spherical) diffraction \n
theory is particularly accessible.\n
\n
No previous knowledge of model sets or diffraction theory is assumed. \n
This is based on joint work with Michael Bjorklund and Felix Pogorzelski.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1977:field_when:0:137
SUMMARY:Mappings with integrally controlled $p$-moduli
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160104T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160104T160000
URL;VALUE=URI:http://math.biu.ac.il/node/1977
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. A. Golberg\, Holon Institute of Technology\n
\n
Abstract:\n
We consider classes of mappings (with controlled moduli) whose $p$-module of \n
the families of curves/surfaces is restricted by integrals containing \n
measurable functions and arbitrary admissible metrics. In the talk \n
we discuss various properties of mappings with controlled moduli including \n
their differential features (Lusin's $N-$ and $N^{-1}$-conditions\, \n
Jacobian bounds\, estimates for distortion dilatations\, \n
H\"older/logarithmically H\"older continuity) and the topological structure \n
(openness\, discreteness\, invertibility\, finiteness of the multiplicity \n
function). This allows us to investigate the interconnection between mappings \n
of bounded and finite distortion defined analytically and mapping with \n
controlled moduli having no analytic assumptions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1922:field_when:0:138
SUMMARY:Stability Versions of Erdos-Ko-Rado Type Theorems via Isoperimetry
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160103T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20160103T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1922
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Noam Lifshitz (BIU)\n
\n
Abstract:\n
Erdos-Ko-Rado (EKR) type theorems yield upper bounds on the size of set \n
families under various intersection requirements on the elements. Stability \n
versions of such theorems assert that if the size of a family is close to the \n
maximum possible then the family itself must be close (in appropriate sense) \n
to a maximum family.\n
\n
In this talk we present an approach to stability versions of EKR-type \n
theorems through isoperimetric inequalities for subsets of the hypercube. We \n
use this approach to obtain tight stability versions of the EKR theorem \n
itself and of the Ahlswede-Khachatrian theorem on t-intersecting families \n
(for k < n/(t+1))\, and to show that\, somewhat surprisingly\, both theorems \n
hold when the "intersection" requirement is replaced by a much weaker \n
requirement. Furthermore\, we obtain stability versions of several recent \n
EKR-type results\, including Frankl's proof of the Erdos matching conjecture \n
for n>(2s+1)k-s.\n
Joint work with David Ellis and Nathan Keller.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1954:field_when:0:139
SUMMARY:Quadratic rational functions with a periodic critical point
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151230T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151230T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1954
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Solomon Vishkautsan (Scuola Normale Superiore di Pisa)\n
\n
Abstract:\n
A rational function defined over the rationals has only finitely many \n
rational preperiodic points by Northcott's classical theorem. These points \n
describe a finite directed graph (with arrows connecting between each \n
preperiodic point and its image under the function). We give a \n
classification\, up to a conjecture\, of all possible graphs of quadratic \n
rational functions with a rational periodic critical point. This \n
generalizes the classification of such graphs for quadratic polynomials over \n
the rationals by Poonen (1998). This is a joint work with Jung Kyu Canci \n
(Universität Basel).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1970:field_when:0:140
SUMMARY:Using Lanczos for nuclear corrections in muonic atoms and the proton radius \n
puzzle
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151229T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151229T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1970
LOCATION:Math seminar room - building 216\, room 201
DESCRIPTION:Speaker: Nir Nevo Dinur - Racah Institute of Physics\, Hebrew U\n
\n
Abstract:\n
The most precise determination of the proton charge radius\, from a novel \n
muonic hydrogen spectroscopy experiment\, disagrees with previous spectroscopy \n
and scattering experiments done with electrons. \n
\n
This 7-sigma discrepancy is known as "proton radius puzzle"\, and may be the \n
result of hitherto unknown physics. \n
\n
In order to investigate it\, experiments with other muonic atoms have been \n
conducted. \n
\n
These experiments rely on accurate theoretical predictions. \n
\n
In particular\, their precision is limited by the nuclear corrections. \n
\n
We have calculated these corrections for muonic atoms with A=3\,4 nucleons\, \n
for the first time using ab-initio methods and state-of-the-art nuclear \n
potentials\, significantly improving previous estimates\, and contributed also \n
to the A=2 case. \n
\n
This was achieved using a newly developed method\, based on the Lanczos \n
algorithm\, for the calculation of energy-dependent sum-rules. \n
\n
Our new method and our results will be presented and discussed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1969:field_when:0:141
SUMMARY:Applications of discrete Schroedinger equations to the standard map
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151227T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151227T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1969
LOCATION:seminar room
DESCRIPTION:Speaker: Mira Shamis\n
\n
Abstract:\n
We shall discuss the Chirikov standard map\, an area-preserving map of the \n
torus to itself in which quasi-periodic and chaotic dynamics are believed to \n
coexist. We shall describe how the problem can be related to the spectral \n
properties of a one-dimensional discrete Schroedinger operator\, and present a \n
recent result.\n
\n
Based on joint work with T. Spencer.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1968:field_when:0:142
SUMMARY:Refined count of plane tropical curves of positive genus
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151220T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151220T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1968
LOCATION:seminar room
DESCRIPTION:Speaker: Eugenii Shustin\n
\n
Abstract:\n
We define refined tropical enumerative invariants counting plane tropical \n
curves of a given degree and a given positive genus and having marked points \n
on edges and at vertices. This extends Block-Goettsche and \n
Goettsche-Schroeter refined tropical invariants. As a consequence we obtain \n
tropical (complex) descendant invariants and (real) broccoli invariants of \n
positive genus.\n
\n
(Joint work with F. Schroeter.)\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1964:field_when:0:143
SUMMARY:Extremal and approximation problems for positive definite functions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151221T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151221T203500
URL;VALUE=URI:http://math.biu.ac.il/node/1964
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Dr. Panagiotis Mavroudis\, University of Crete\, Greece\n
\n
Abstract:\n
Let $\Omega$ be an open 0-symmetric subset of $\mathbb R^d$ which contains 0 \n
and\n
f a continuous positive definite function vanishing off O\, that is\,\n
supp f is contained in the closure of $\Omega$. The problem is to approximate\n
f by a continuous positive definite function F supported in $\Omega$. We \n
prove\n
this when 1. d=1. 2 $\Omega$ is strictly star-shaped 3. f is a radial \n
function.\n
We also consider the following problem: Given a measure $\mu$\n
supported in $\Omega$\, does there exist an extremal function for the \n
problem\n
$\sup \int f d\mu$\, where the sup is taken over the cone of continuous\n
positive definite functions f supported in $\Omega$ with f(0)=1?
END:VEVENT
BEGIN:VEVENT
UID:calendar:1961:field_when:0:144
SUMMARY:Node-weighted minimal Steiner trees logarithmic approximation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151215T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151215T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1961
LOCATION:Math seminar room - building 216\, room 201
DESCRIPTION:Speaker: Tomer Davidor and Ido Spector - BIU\n
\n
Abstract:\n
In this lecture we present an improvement to the running time of the Philip \n
Klein and R.Ravi approximation algorithm. The Philip-Klein algorithm produces \n
a Steiner Tree that is close to the minimal one\, by preforming iterations \n
repeatedly. The iteration implementation is based on the distances between \n
the nodes of the graph. The main hypothesis that led to our improvement is \n
that there is no need to find all the distances in the graph but only a part \n
of them. In addition\, an example of the algorithm's implementation will be \n
shown. \n
\n
Joint work with Eli Packer\, IBM\, and Shlomo Yanetz
END:VEVENT
BEGIN:VEVENT
UID:calendar:1958:field_when:0:145
SUMMARY:On rings stable under derivations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151216T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151216T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1958
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Leonid Makar-Limanov (Wayne State University)\n
\n
Abstract:\n
Let z be an algebraic function of n variables and A(z) the algebra \n
generated by all variables and all partial derivatives of z (of all \n
orders). If z is a polynomial then A(z) is just a polynomial algebra\, but \n
when z is not a polynomial then it is not clear what is the structure of \n
this algebra. I'll report on known cases and formulate a conjecture.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1957:field_when:0:146
SUMMARY:Statistical modelling of neuronal assemblies underneath a recording electrode
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151208T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151208T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1957
LOCATION:Math seminar room\, building 216 room 208
DESCRIPTION:Speaker: Lilach Avitan - University of Queensland\n
\n
Abstract:\n
The brain contains billions of neurons each connected to several thousand \n
other neurons. The voltage recorded over the scalp/skull is generated by \n
activity of large population of neurons. Different recorded amplitudes at \n
different states of vigilance are attributed to differences in synchrony \n
level among neurons and different statistical structures of the population\; \n
however the relation between the signals and the statistical characteristics \n
of the underlying neural activity is still an open question. We developed a \n
model based on multidimensional stationary stochastic processes to resolve \n
the statistical organization properties of neural assemblies. We showed that \n
despite the many possible options for statistical organizations only very few \n
are mathematically plausible.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1926:field_when:0:147
SUMMARY:Generalized RSK
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151220T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151220T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1926
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Arkady Berenstein (Univ of Oregon)\n
\n
Abstract:\n
The goal of my talk (based on joint work with Dima Grigoriev\, Anatol \n
Kirillov\, and Gleb Koshevoy) is to generalize the celebrated \n
Robinson-Schensted-Knuth (RSK) bijection between the set of matrices with \n
nonnegative integer entries\, and the set of the planar partitions.\n
\n
\n
\n
Namely\, for any pair of injective valuations on an integral domain we \n
construct a canonical bijection K\, which we call the generalized RSK\, between \n
the images of the valuations\, i.e.\, between certain ordered abelian monoids.\n
\n
\n
\n
Given a semisimple or Kac-Moody group\, for each reduced word ii=(i_1\,...\,i_m) \n
for a Weyl group element we produce a pair of injective valuations on \n
C[x_1\,...\,x_m] and argue that the corresponding bijection K=K_ii\, which maps \n
the lattice points of the positive octant onto the lattice points of a convex \n
polyhedral cone in R^m\, is the most natural generalization of the classical \n
RSK and\, moreover\, K_ii can be viewed as a bijection between Lusztig and \n
Kashiwara parametrizations of the dual canonical basis in the corresponding \n
quantum Schubert cell.\n
\n
\n
\n
Generalized RSKs are abundant in ``nature"\, for instance\, any pair of \n
polynomial maps phi\,psi:C^m-->C^m with dense images determines a pair of \n
injective valuations on C[x_1\,...\,x_n] and thus defines a generalized RSK \n
bijection K_{phi\,psi} between two sub-monoids of Z_+^m.\n
\n
\n
\n
When phi and psi are birational isomorphisms\, we expect that K_{phi\,psi} has \n
a geometric ``mirror image"\, i.e.\, that there is a rational function f on C^m \n
whose poles complement the image of phi and psi so that the tropicalization \n
of the composition psi^{-1}phi along f equals to K_{phi\,psi}. We refer to \n
such a geometric data as a (generalized) geometric RSK\, and view f as a \n
``super-potential." This fully applies to each ii-RSK situation\, and we find \n
a super-potential f=f_ii which helps to compute K_ii.\n
\n
\n
\n
While each K_ii has a ``crystal" flavor\, its geometric (and mirror) \n
counterpart f_ii emerges from the cluster twist of the relevant double Bruhat \n
cell studied by Andrei Zelevinsky\, David Kazhdan\, and myself.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1955:field_when:0:148
SUMMARY:Superdimension of Lie superalgebra representations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151209T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151209T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1955
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Shifra Reif (ORT Braude College)\n
\n
Abstract:\n
We shall discuss the notion of superdimension and methods to compute it for \n
simple modules of basic Lie superalgebras. We give a superdimension formula \n
for modules over the general linear Lie superalgebra and propose ideas on how \n
one should approach the general case. Joint with Chmutov and Karpman.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1953:field_when:0:149
SUMMARY:Arithmetic statistics in function fields
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151223T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151223T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1953
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Edva Roditty-Gershon (University of Bristol)\n
\n
Abstract: One of the most famous conjectures in number theory is \n
the Hardy-Littlewood conjecture\, which gives an asymptotic for the number of \n
integers n up to X such that for a given tuple of integers a_1\,..\, a_k all \n
the numbers n+a_1\,..\, n+a_k are prime. This quantifies and generalises the \n
twin-prime conjecture.\n
\n
\n
Function field analogue of this problem has recently been resolved in the \n
limit of large finite field size q by Lior Bary-Soroker. However\, in this \n
limit the correlations disappear: the arithmetic functions become \n
uncorrelated. It is therefore important to understand the terms of lower \n
order in q\, which must account for the correlations. We compute averages of \n
these terms which detect correlations. Our results show that there is \n
considerable cancellation in the averaging and have implications for the rate \n
at which correlations disappear when q tends to infinity. This is a joint \n
work with Jon Keating
END:VEVENT
BEGIN:VEVENT
UID:calendar:1952:field_when:0:150
SUMMARY:The Emergence of Pattern in Random Processes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151206T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151206T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1952
LOCATION:seminar room
DESCRIPTION:Speaker: William I. Newman (UCLA)\n
\n
Abstract:\n
We consider both time series as well as spatial distributions (in 1-4 \n
dimensions). In the first\, we observe that time series for individual and \n
independently deviating random variables can manifest pattern through the \n
emergence of peak-to-peak sequences that are visible to the eye yet fail all \n
Fourier analysis schemes and reveal a seeming periodicity of 3-events per \n
cycle. We note that this can explain observations of apparent cycles in \n
mammalian animal populations. We consider models\, as well\, based on the \n
Langevin equation of kinetic theory and the Smolouchowski relation that \n
present circumstances where the apparent period can vary from 3-4 and\, for a \n
special subclass of problems\, to periods between 2 and 3. We explore how \n
cataloged observational data from global earthquake catalogues\, \n
magnetospheric AL index observations\, Old Faithful Geyser eruption data\, and \n
the performance of the Standard & Poor's 500 index (percent daily variation) \n
manifest different degrees of statistical agreement with the theory we \n
derived. We present a simple model for many mammalian population cycles \n
whose underlying phenomenological basis has strong biological \n
implications. We then employ directed graphs to explore \n
nearest-neighbor relationships and isolate the character of spatial \n
clustering in 1-4 dimension. We observe that the one-dimensional problem is \n
formally equivalent to that presented by peak-to-peak sequences in time \n
series and also demonstrates a mean number of points per cluster of 3 in \n
one dimension. We then take the first moment of each of the clusters formed\, \n
and observed that they too form clusters. We observe the emergence of a \n
hierarchy of clusters and the emergence of universal cluster numbers\, \n
analogous to branching ratios and\, possibly\, Feigenbaum numbers. These\, in \n
turn\, are related to fractals as well as succularity and lacunarity\, although \n
the exact nature of this connection has not been identified. Finally\, we \n
show how hierarchical clustering emerging from random distributions may help \n
provide an explanation for observations of hierarchical clustering in \n
cosmology via the virial theorem and simulation results relating to the \n
gravitational stabilization in a self-similar way of very large \n
self-gravitating ensembles.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1951:field_when:0:151
SUMMARY:Tiling by translates of a function
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151207T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151207T230500
URL;VALUE=URI:http://math.biu.ac.il/node/1951
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Dr. Nir Lev\, Bar-Ilan University\n
\n
Abstract:\n
A function f on the real line is said to tile by translates\n
along a discrete set $\Lambda$ if the sum of all the functions\n
f(x-\lambda)\, $\lambda \in \Lambda$\, is equal to one identically.\n
Which functions can tile by translates\, and what can be said\n
about the translation set $\Lambda$? I will survey the subject and\n
discuss some recent results joint with Mihail Kolountzakis.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1949:field_when:0:152
SUMMARY:Absolute Galois groups - old and new results
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151129T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151129T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1949
LOCATION:seminar room
DESCRIPTION:Speaker: Ido Efrat (BGU)\n
\n
Abstract:\n
These symmetry patterns are described by the absolute Galois group of the \n
field\, whose\n
structure is in general still a mystery.\n
\n
We will describe what is known about this symmetry group: classical facts\, \n
consequences \n
of the epochal work by Veovodsky and Rost\, and very recent structural results \n
and conjectures\n
related to higher cohomology operations and intersection theorems.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1948:field_when:0:153
SUMMARY:A tale of two Hardy spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151123T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151123T182000
URL;VALUE=URI:http://math.biu.ac.il/node/1948
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. E. Liflyand Bar-Ilan University\n
\n
Abstract:\n
New relations between the Fourier transform of a function of bounded\n
variation and the Hilbert transform of its derivative are revealed.\n
The main result is an asymptotic formula for the {\f cosine} Fourier\n
transform. Such relations have previously been known only for the sine\n
Fourier transform. Interrelations of various function spaces are studied\n
in this context\, first of all of two types of Hardy spaces. The obtained\n
results are used for proving completely new results on the integrability\n
of trigonometric series.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1947:field_when:0:154
SUMMARY:Coupled nonlinear Schrödinger equations\, Lotka-Volterra models\, and control \n
of soliton collisions in broadband optical waveguide systems
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151124T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151124T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1947
LOCATION:Math seminar room - building 216\, room 201
DESCRIPTION:Speaker: Avner Peleg - Afeka College\n
\n
Abstract:\n
\n
\n
Transmission rates in broadband optical waveguide systems are enhanced by \n
launching\n
many pulse sequences through the same waveguide. Since pulses from different \n
sequences\n
propagate with different group velocities\, intersequence pulse collisions are \n
frequent\, and can lead\n
to severe transmission degradation. On the other hand\, the energy exchange in \n
pulse collisions can\n
be beneficially used for controlling the transmission.\n
\n
In this work we show that collision-induced amplitude dynamics of soliton \n
sequences of N\n
perturbed coupled nonlinear Schrödinger (NLS) equations can be described by \n
N-dimensional\n
Lotka-Volterra (LV) models\, where the model's form depends on the \n
perturbation. To derive the LV\n
models\, we first carry out single-collision analysis\, which is based on the \n
method of eigenmode\n
expansion with the eigenmodes of the linear operator describing small \n
perturbations about the\n
fundamental NLS soliton. We use stability and bifurcation analysis for the \n
equilibrium points of the\n
LV models to develop methods for achieving robust transmission stabilization \n
and switching that\n
work well for a variety of waveguides. Further enhancement of transmission \n
stability is obtained in\n
waveguides with a narrowband Ginzburg-Landau gain-loss profile. We also \n
discuss the possibility\n
to use the relation between NLS and LV models to realize transition to \n
spatio-temporal chaos with\n
NLS solitons.\n
\n
\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1913:field_when:0:155
SUMMARY:Some surprising identities in character tables of S_n
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151122T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151122T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1913
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Amitai Regev (Weizmann)\n
\n
Abstract:\n
On page 155 of [Graham\, Knuth and Patashnik] it says:\n
\n
\n
\n
The numbers in Pascal's triangle satisfy\, practically speaking\, infinitely \n
many identities\,\n
\n
so it is not surprising that we can find some surprising relationships by \n
looking closely.\n
\n
\n
\n
By proving some surprising identities in character tables of S_n we shall \n
indicate that a\n
\n
similar statement seem to hold for the S_n character tables .\n
\n
Joint work with D. Zeilberger\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1914:field_when:0:156
SUMMARY:Almost simplicial polytopes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151129T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151129T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1914
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Eran Nevo (Hebrew U)\n
\n
Abstract: We study $n$-vertex $d$-dimensional polytopes with at most one \n
nonsimplex facet with\, say\, $d+s$ vertices\, called almost simplicial \n
polytopes. \n
We provide tight lower and upper bound theorems for these polytopes as \n
functions of $d\,n$ and $s$\, thus generalizing the classical Lower Bound \n
Theorem by Barnette and Upper Bound Theorem by McMullen\, which treat the case \n
$s=0$. We characterize the minimizers and provide examples of maximizers\, for \n
any $d$.\n
\n
Time permitting\, I'll also discuss results on reconstruction problems for \n
these and for related polytopes.\n
\n
This is joint work with Guillermo Pineda-Villavicencio [1]\, Julien Ugon \n
[2]\, David Yost [3].\n
\n
\n
\n
[1] http://front.math.ucdavis.edu/author/G.Pineda-Villavicencio\n
[2] http://front.math.ucdavis.edu/author/J.Ugon\n
[3] http://front.math.ucdavis.edu/author/D.Yost
END:VEVENT
BEGIN:VEVENT
UID:calendar:1934:field_when:0:157
SUMMARY:The Danzer problem and a solution to a related problem of Gowers
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151122T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151122T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1934
LOCATION:seminar room
DESCRIPTION:Speaker: Yaar Solomon (Stony Brook University)\n
\n
Abstract:\n
Is there a point set Y in R^d\, and C>0\, such that every convex set of volume \n
1 contains at least one point of Y and at most C? This discrete geometry \n
problem was posed by Gowers in 2000\, and it is a special case of an open \n
problem posed by Danzer in 1965. I will present two proofs that answers \n
Gowers' question with a NO. The first approach is dynamical\; we introduce a \n
dynamical system and classify its minimal subsystems. This classification in \n
particular yields the negative answer to Gowers' question. The second proof \n
is direct and it has nice applications in combinatorics. The talk will be \n
accessible to a general audience. [This is a joint work with Omri Solan and \n
Barak Weiss]. \n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1932:field_when:0:158
SUMMARY:Asymptotic Properties and Stability of Delay Differential Equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151117T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151117T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1932
LOCATION:Math seminar room - building 216\, room 201
DESCRIPTION:Speaker: Alexander Domoshnitsky - Ariel\n
\n
Abstract:\n
Delays\, arising in nonoscillatory and stable ordinary differential equations\, \n
can induce oscillation and instability of their solutions. That is why the \n
traditional direction in the study of nonoscillation and stability of delay \n
equations is to establish a smallness of delay\, allowing delay differential \n
equations to preserve these convenient properties of ordinary differential \n
equations with the same coefficients. In this talk\, we find cases in which \n
delays\, arising in oscillatory and asymptotically unstable ordinary \n
differential equations\, induce nonoscillation and stability of delay \n
equations. We demonstrate that\, although the ordinary differential equation \n
x"(t)+c(t)x(t)=0 can be oscillating and asymptoticaly unstable\, the delay \n
equation x"(t)+a(t)x(t-h(t))-b(t)x(t-g(t))=0\, where c(t)=a(t)-b(t)\, can be \n
nonoscillating and exponentially stable. Results on nonoscillation and \n
exponential stability of delay differential equations are obtained. On the \n
basis of these results on nonoscillation and stability\, the new possibilities \n
of non-invasive (non-evasive) control\, which allow us to stabilize a motion \n
of single mass point\, are proposed. Stabilization of this sort\, according to \n
common belief requires damping term in the second order differential \n
equation. Results obtained in this paper refute this delusion.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1931:field_when:0:159
SUMMARY:Asymptotic Properties and Stability of Delay Differential Equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151117T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151117T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1931
LOCATION:Math seminar room - building 216\, room 201
DESCRIPTION:Speaker: Alexander Domoshnitsky - Ariel\n
\n
Abstract:\n
Delays\, arising in nonoscillatory and stable ordinary differential equations\, \n
can induce oscillation and instability of their solutions. That is why the \n
traditional direction in the study of nonoscillation and stability of delay \n
equations is to establish a smallness of delay\, allowing delay differential \n
equations to preserve these convenient properties of ordinary differential \n
equations with the same coefficients. In this talk\, we find cases in which \n
delays\, arising in oscillatory and asymptotically unstable ordinary \n
differential equations\, induce nonoscillation and stability of delay \n
equations. We demonstrate that\, although the ordinary differential equation \n
x"(t)+c(t)x(t)=0 can be oscillating and asymptoticaly unstable\, the delay \n
equation x"(t)+a(t)x(t-h(t))-b(t)x(t-g(t))=0\, where c(t)=a(t)-b(t)\, can be \n
nonoscillating and exponentially stable. Results on nonoscillation and \n
exponential stability of delay differential equations are obtained. On the \n
basis of these results on nonoscillation and stability\, the new possibilities \n
of non-invasive (non-evasive) control\, which allow us to stabilize a motion \n
of single mass point\, are proposed. Stabilization of this sort\, according to \n
common belief requires damping term in the second order differential \n
equation. Results obtained in this paper refute this delusion.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1930:field_when:0:160
SUMMARY:Koszul algebras\, quadratic duals\, and Galois cohomology
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151202T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151202T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1930
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Claudio Quadrelli (Ben-Gurion University)\n
\n
Abstract:\n
See attached file.\n
\n
http://math.biu.ac.il/files/math/seminars/barilan.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:1929:field_when:0:161
SUMMARY:The metaplectic Shalika model and symmetric square L-function
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151125T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151125T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1929
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Eyal Kaplan (Ohio State University)\n
\n
Abstract: One of the tools frequently used in the study of group \n
representations and L-functions is called a model. Roughly speaking\, a model \n
is a unique realization of a representation in a convenient space of \n
functions on the group. We will discuss examples of models on linear and \n
covering groups. We will present a novel model: the metaplectic Shalika \n
model. This is the analog of the Shalika model of GL(2n) of Jacquet and \n
Shalika. One interesting representation having this model is the so-called \n
exceptional representation of Kazhdan and Patterson\, which is the analog for \n
linear groups of the Weil representation. This representation is truly \n
exceptional. We will describe it and its role in the study of \n
the symmetric square L-function\, and related problems.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1928:field_when:0:162
SUMMARY:Quantifying isolated singularity in DEs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151116T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151116T180000
URL;VALUE=URI:http://math.biu.ac.il/node/1928
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Y. Krasnov Bar-Ilan University\n
\n
Abstract:\n
Consider a polynomial map $f: C^n\to C^n$\, vanishing at some point $z_0$ in \n
$C^n$. In differential equations\, such points are called\n
equilibria of the vector field $z' = f(z)$\, or their singular points. The \n
question is "how singular". Can we quantify the singularity of $f$ at $z_0$?\n
Attempting only to demystify the problem\, in this presentation we make an \n
effort to quantify singularity in the sense of differential equations\n
and also discuss connections of this theory to analysis\, topology and \n
commutative algebra.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1927:field_when:0:163
SUMMARY:Symbol length in the Brauer group of a field
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151115T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151115T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1927
LOCATION:seminar room
DESCRIPTION:Speaker: Eli Matzri\n
\n
Abstract: The Merkurjev-Suslin Theorem tell us that the n-torsion part of the \n
Brauer group of a field containing a primitive n-th root of 1 is generated by \n
symbol algebras. A natural question is:What can be said on the minimal number \n
of symbols needed. In this talk I will survey some of the known results and \n
give the idea for the proof for a bound in a geometric situation (by which I \n
mean when the base field contains an algebraically closed field).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1923:field_when:0:164
SUMMARY:Some new partial answers to a 52 year old interpolation question
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151109T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151109T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1923
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. M. Cwikel\, Technion\n
\n
Abstract:\n
It is now more than 52 years since Studia Mathematica received Alberto\n
Calder\'on's very remarkable paper about his theory of complex\n
interpolation spaces. And one of the questions which Calder\'on\n
implicitly asked in that paper\, by solving it in a significant special\n
case\, is apparently still open today:\n
\n
DOES COMPLEX INTERPOLATION PRESERVE THE COMPACTNESS OF AN OPERATOR?\n
\n
After briefly surveying attempts to solve this question over several\n
decades\, I will also report on a few new partial answers obtained\n
recently\, some of them (arXiv:1411.0171) jointly with Richard\n
Rochberg. Among other things there is an interplay with Jaak Peetre's\n
"plus-minus" interpolation method\, (arXiv:1502.00986) a method which\n
probably deserves to be better known. Banach lattices and UMD spaces\n
also have some roles to play.\n
\n
Several distinguished mathematicians have expressed the belief that\n
that the general answer to this question will ultimately turn out to be\n
negative. Among other things\, I will try to hint at where a counterexample\n
might perhaps be hiding. You are all warmly invited to seek it out\,\n
or prove that it does not exist.\n
\n
A fairly recent survey which discusses this question is available at\n
arXiv:1410.4527.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1916:field_when:0:165
SUMMARY:Branching rules for wreath products
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151227T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151227T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1916
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Itamr Stein (BIU)\n
\n
Abstract:\n
The branching rules for representations of the symmetric group are one of the \n
gems of representation theory. In this talk we will give a natural \n
generalization of some branching rules to the case of a wreath product of a \n
finite group with the symmetric group. \n
\n
The rules we will generalize are the Littlewood-Richardson rule and the \n
"classical" rules for inducting from S_{n} to S_{n+1} and restricting from \n
S_{n+1} to S_{n}. If time allows we will give an application to the quiver \n
computation of a natural family of categor algebras.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1909:field_when:0:166
SUMMARY:On the correlation of monotone families
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151025T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151025T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1909
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Nathan Keller (BIU)\n
\n
Abstract:\n
The classical correlation inequality of Harris asserts that any two monotone \n
increasing families on the discrete cube are nonnegatively correlated. In \n
1996\, Talagrand established a lower bound on the correlation in terms of how \n
much the two families depend simultaneously on the same coordinates. \n
Talagrand's method and results inspired a number of important works in \n
combinatorics and probability theory.\n
\n
\n
\n
In this talk we present stronger correlation lower bounds that hold when the \n
increasing families satisfy natural regularity or symmetry conditions. In \n
addition\, we present several new classes of examples for which Talagrand's \n
bound is tight.\n
\n
\n
\n
A central tool we use is a simple lemma asserting that for monotone events \n
noise decreases correlation. This lemma gives also a very simple derivation \n
of the classical FKG inequality for product measures\, and leads to a \n
simplification of part of Talagrand's proof.\n
\n
\n
\n
Joint work with Gil Kalai and Elchanan Mossel
END:VEVENT
BEGIN:VEVENT
UID:calendar:1911:field_when:0:167
SUMMARY:Schur positivity via pattern avoidance
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151101T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151101T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1911
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Yuval Roichman (BIU)\n
\n
Abstract:\n
Characterizing sets of permutations whose associated quasi-symmetric function \n
is symmetric and Schur-positive is a long-standing problem in algebraic \n
combinatorics. We will explain the significance of the problem and describe \n
recent progress.\n
\n
\n
\n
A general method to construct Schur-positive sets and multisets\, based on \n
pattern avoidance and geometric grids will be presented. This approach \n
produces many new instances of Schur-positive sets\, and provides a broad \n
framework that explains the existence of known such sets that until now were \n
sporadic cases.\n
\n
\n
\n
Joint with Sergi Elizalde.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1915:field_when:0:168
SUMMARY:On Shellability\, Cohen-Macauleyness and the Homotopy Type of Boolean \n
Representable Simplicial Complexes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151115T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151115T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1915
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Stuart Margolis (BIU)\n
\n
Abstract: Boolean representable simplicial complexes are a generalization of \n
matroids based on independence over the Boolean semiring. The work was \n
pioneered by work of Izhakian and Rowen at Bar-Ilan on notions of rank and \n
independence over semirings. It was later defined and initially developed \n
by Izhakian and Rhodes and later Silva. In this talk it is proved that \n
fundamental groups of boolean representable simplicial complexes are free and \n
the rank is determined by the number and nature of the connected components \n
of their graph of flats for dimension ≥ 2. In the case of dimension 2\, it \n
is shown that boolean representable simplicial complexes have the homotopy \n
type of a wedge of spheres of dimensions 1 and 2. Also in the case of \n
dimension 2\, necessary and sufficient conditions for shellability and being \n
sequentially Cohen-Macaulay are determined. These notions are equivalent in \n
dimension 2\, but despite having the appropriate homotopy type\, not all 2 \n
dimensional boolean representable simplicial complexes are shellable. \n
Complexity bounds are provided for all the algorithms involved. All terms \n
will be defined. This is joint work of the speaker\, John Rhodes and Pedro \n
Silva.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1912:field_when:0:169
SUMMARY:Short paths in expander graphs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151108T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151108T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1912
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Klim Efremenko (Tel-Aviv U)\n
\n
Abstract:\n
In this talk we study short edge-disjoint paths in expander graphs(here it \n
mean: graph with constant mixing time). We use the Lovasz Local Lemma to \n
prove the following result: Given a d-regular expander graph G and a set \n
L={(s_i\,t_i)} such that each vertex of G appears at most O(d) times in the \n
list\, there exist a set of edge disjoint paths of constant length connecting \n
each s_i to t_i. This result has applications to multiparty computation \n
performed over networks in the presence of random noise.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1920:field_when:0:170
SUMMARY:The bridge that Arthyr Cayley built
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151108T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151108T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1920
LOCATION:seminar room
DESCRIPTION:Speaker: Boris Kunyavskii (Bar-Ilan University)\n
\n
Abstract:\n
In 1846\, Arthur Cayley defined a correspondence between orthogonal\n
matrices of determinant one and skew-symmetric matrices. This\n
observation was a starting point of a long (and yet unfinished)\n
story. In the talk we will overview its highlights\, with a focus on\n
the achievements obtained during the past decade and some open\n
problems.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1919:field_when:0:171
SUMMARY:Hardy spaces on the Klein-Dirac quadric and multidimensional annulus: \n
applications to Interpolation\, Moment problems\, and Cubature
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151026T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151101T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1919
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Ognyan Kounchev IZKS\, University of Bonn\, Germany Institute of \n
mathematics and informatics\, Bulgarian Academy of Sciences\n
\n
Abstract:\n
We present a new construction of Hardy spaces on the Klein-Dirac\n
quadric\; we show that the quadric is obtained as a complexification of the\n
unit ball in R^n. We introduce also Hardy spaces on complexified\n
multidimensional annulus.\n
We show some natural properties of these Hardy spaces\, in particular\,\n
Cauchy type formula\, and Brothers Riesz type theorem.\n
We prove applications to the multidimensional Moment problem\,\n
multidimensional Interpolation theory\, and Cubature formulas.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1907:field_when:0:172
SUMMARY:Unique factorization of tensor products for finite dimensional simple Lie \n
algebras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151111T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151111T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1907
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. R. Venkatesh (Weizmann Institute of Science)\n
\n
Abstract:\n
Suppose V is a finite dimensional representation of a complex finite \n
dimensional simple Lie algebra that can be written as a tensor product of \n
irreducible representations. A theorem of C.S. Rajan states that the \n
non-trivial irreducible factors that occur in the tensor product \n
factorization of V are uniquely determined\, up to reordering\, by the \n
isomorphism class of V. I will present an elementary proof of Rajan's \n
theorem. This is a joint work with S.Viswanath.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1904:field_when:0:173
SUMMARY:The weight\, density and Lindelof number in spaces and topological groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151025T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151025T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1904
LOCATION:The weight\, density and Lindelof number in spaces and topological groups
DESCRIPTION:Speaker: Mikhail G. Tkachenko\n
\n
Abstract:\n
Attached [1]\n
\n
http://math.biu.ac.il/files/math/seminars/abstracttkachenko-2.pdf\n
\n
[1] http://math.biu.ac.il/files/math/seminars/abstracttkachenko-2.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:1895:field_when:0:174
SUMMARY:Sums of two squares in function fields
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151021T110000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151021T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1895
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Ofir Gorodetsky (Tel Aviv University)\n
\n
Abstract:\n
>Fermat was the first to characterize which integer numbers are sums of two \n
>perfect squares. A natural question of analytical number theory is: How many \n
>integers up to x are of that form? Landau settled this question using \n
>Dirichlet series and complex analysis. We'll discuss Landau's proof and \n
>present recent results on the corresponding problem over the rational \n
>function field over a finite field\, which requires new ideas.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1896:field_when:0:175
SUMMARY:Counting points and counting representations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151104T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151104T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1896
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Nir Avni (Northwestern University)\n
\n
Abstract: I will talk about the following questions: 1) \n
Given a system of polynomial equations with integer coefficients\, how many \n
solutions does it have in the ring Z/N?\n
\n
2) Given a polynomial map f:R^a-->R^b and a smooth\, compactly \n
supported measure m on R^a\, does the push-forward of m by f have bounded \n
density? 3) Given a lattice in a higher rank Lie group (say\, SL(n\,Z) for \n
n>2). How many d-dimensional representations does it have? I will \n
explain how these questions are related to the singularities of certain \n
varieties. Along the way\, I'll talk about canonical singularities\, random \n
commutators\, and the moduli space of local systems. This is a joint \n
work with Rami Aizenbud
END:VEVENT
BEGIN:VEVENT
UID:calendar:1892:field_when:0:176
SUMMARY:Finitary 2-categories and their 2-representations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151028T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20151028T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1892
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Volodymyr Mazorchuk (Uppsala University)\n
\n
Abstract:\n
In this talk I will give a survey of that part of higher representation \n
theory which studies finitary 2-categories and their 2-representations. The \n
plan is to present basic definitions\, constructions\, and results\, and then \n
describe some external applications.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1578:field_when:0:177
SUMMARY:On the Trade-off Between Equivalence Constraints and Labels
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150621T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150621T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1578
LOCATION:Department Seminar Room\, Building 216 Room 201
DESCRIPTION:Speaker: Liat Ein-Dor - IBM Research\n
\n
Abstract:\n
Supervised learning is based predominantly on labeled examples which \n
are often expensive and scarce. An alternative form of supervision is \n
equivalence constraints\, i.e. two examples which are known to be from the \n
same/different classes\, yet their class labels are unknown. Equivalence \n
constraints are often easier and cheaper to obtain\, but the theoretical \n
underpinnings of their \n
learning utility relative to labels is still lacking. In this work we develop novel framework \n
for analyzing the learning utility of equivalence constraints. \n
Specifically\, we extend the statistical mechanics Perceptron capacity \n
calculations\, used thus far only for labeled data\, to supervised learning \n
from equivalence constraints. We then derive generalization bounds for \n
training with equivalence constraints\, using a link between Perceptron \n
capacity and Rademacher complexity. We prove that for large sample sizes\, a \n
sample with EC supervision becomes as powerful as a fully labeled sample of \n
the same size. We also prove that this result holds even when the examples in \n
the constraints are highly correlated.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1576:field_when:0:178
SUMMARY:Majorization inequalities for valuations of eigenvalues using tropical \n
algebra
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150624T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150624T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1576
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Marianne Akian (INRIA Saclay--Ile-de-France and CMAP\, Ecole \n
Polytechnique)\n
\n
Abstract:\n
We consider a matrix with entries over the field of Puiseux series\,\n
equipped with its non-archimedean valuation (the leading exponent).\n
We establish majorization inequalities relating the\n
sequence of the valuations of the eigenvalues of a matrix\n
with the tropical eigenvalues of its valuation matrix\n
(the latter is obtained by taking the valuation entrywise).\n
We also show that\, generically in the leading coefficients of the\n
Puiseux series\, the precise asymptotics of eigenvalues\, eigenvectors\n
and condition numbers can be determined.\n
For this\, we apply diagonal scalings constructed from\n
the dual variables of a parametric optimal assignment constructed from\n
the valuation matrix.\n
Next\, we establish an archimedean analogue of the above inequalities\,\n
which applies to matrix polynomials with coefficients in\n
the field of complex numbers\, equipped with the modulus as its valuation.\n
In particular\, we obtain log-majorization inequalities for the eigenvalues\n
which involve combinatorial constants depending on the pattern of the \n
matrices.\n
This talk covers joint works with Ravindra Bapat\, Stéphane Gaubert\,\n
Andrea Marchesini\, and Meisam Sharify.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1575:field_when:0:179
SUMMARY:Convexity and Teichm\"{u}ller spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150608T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150608T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1575
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. S. Krushkal\, Bar-Ilan University\n
\n
Abstract:\n
We provide restricted negative answers to the Royden-Sullivan problem\n
whether any Teichm\"{u}ller space of dimension greater than $1$\n
is biholomorphically equivalent to bounded domain in a complex Banach\n
space. The only known result here is Tukia's theorem of 1977 that there is\n
a real analytic homeomorphism of the universal Teichm\"{u}ller\n
space onto a convex domain in some Banach space.\n
We prove:\n
(a) Any Teichm\"{u}ller space $\mathbf T(0\,n)$ of the punctured spheres\n
(the surfaces of genus zero) with sufficiently large number of punctures\n
$(n \ge n_0 > 4)$ cannot be mapped biholomorphically onto a bounded\n
convex domain in $\mathbf C^{n-3}$.\n
(b) The universal Teichm\"{u}ller space is not biholomorphically equivalent\n
to a bounded convex domain in uniformly convex Banach space\, in\n
particular\, to convex domain in the Hilbert space.\n
The proofs involve the existence of conformally rigid domains established\n
by Thurston and some interpolation results for bounded univalent functions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1574:field_when:0:180
SUMMARY:Wavelets on fractals
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150601T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150601T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1574
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Palle Jorgensen\, University of Iowa\, USA\n
\n
Abstract:\n
The class of fractals referred to are those which may be specified by a \n
finite system of affine transformations\,\n
assuming contractive scaling\; and their corresponding selfsimilar measures\, \n
$\mu$. They include standard Cantor\n
spaces such as the middle third\, and the planar Sierpinski caskets in various \n
forms\, and their corresponding\n
selfsimilar measures\, but the class is more general than this\; including \n
fractals realized in $\mathbb R^d$\, for\n
$d > 2$.\n
In part 1\, we motivate the need for wavelets in the harmonic analysis of \n
these selfsimilar measures $\mu$. While\n
classes of the Hilbert spaces $L^2(\mu)$ have Fourier bases\, it is known (the \n
speaker and Pedersen) that many do\n
not\, for example the middle third Cantor can have no more than two orthogonal \n
Fourier frequencies.\n
In part 2 of the talk\, we outline a construction by the speaker and Dutkay to \n
the effect that all the affine systems\n
do have wavelet bases\; this entails what we call thin Cantor spaces.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1573:field_when:0:181
SUMMARY:Tropical totally positive matrices
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150617T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150617T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1573
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Adi Niv (INRIA Saclay Ile-de-France and Ecole Polytechnique)\n
\n
Abstract:\n
We start by presenting Gaubert's symmetrized tropical semiring\, which defines \n
a tropical additive-inverse and uses it to resolve tropical singularity. \n
Then\, we recall properties of totally positive matrices over rings\, define \n
tropical total positivity and total non-negativity of matrices using the \n
symmetrized structure\, and state combinatorial and algebraic properties of \n
these matrices. By studying the tropical semiring via valuation on the field \n
of Puiseux series\, we relate the tropical properties to the classical ones.\n
Joint work with Stephane Gaubert
END:VEVENT
BEGIN:VEVENT
UID:calendar:1572:field_when:0:182
SUMMARY:Optimal interpolating spaces generated by the Abel-Jacobi elliptic functions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150531T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150531T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1572
LOCATION:Department room
DESCRIPTION:Speaker: Prof. Boris Levit\, Queen's University\, Kingston\, Canada\n
\n
Abstract: The classical Abel-Jacobi elliptic functions have been extensively \n
used in the Approximation Theory and\, in particular\, in the Optimal \n
Recovery problems. Such functions posses a variety of very attractive \n
properties\, being much more exible and versatile in comparison to the \n
circular functions. I will consider several examples of linear interpolating \n
spaces generated by such functions. A notion of an optimal interpolating \n
space will be discussed\, drawing on some applications in statistical \n
problems of random data approximation. Conditions will be presented under \n
which the interpolating spaces generated by the Abel-Jacobi elliptic \n
functions contain constants and are optimal\, in the case of equidistant \n
interpolating design. I will also mention some open problems related to a \n
possible extension of these results to the more general class \n
of automorphic functions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1571:field_when:0:183
SUMMARY:Optimal interpolating spaces generated by the Abel-Jacobi elliptic functions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150531T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150531T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1571
LOCATION:Department room
DESCRIPTION:Speaker: Prof. Boris Levit\, Queen's University\, Kingston\, Canada\n
\n
Abstract: The classical Abel-Jacobi elliptic functions have been extensively \n
used in the Approximation Theory and\, in particular\, in the Optimal \n
Recovery problems. Such functions posses a variety of very attractive \n
properties\, being much more exible and versatile in comparison to the \n
circular functions. I will consider several examples of linear interpolating \n
spaces generated by such functions. A notion of an optimal interpolating \n
space will be discussed\, drawing on some applications in statistical \n
problems of random data approximation. Conditions will be presented under \n
which the interpolating spaces generated by the Abel-Jacobi elliptic \n
functions contain constants and are optimal\, in the case of equidistant \n
interpolating design. I will also mention some open problems related to a \n
possible extension of these results to the more general class \n
of automorphic functions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1569:field_when:0:184
SUMMARY:On the Zariski Cancellation Problem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150528T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150528T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1569
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. Mikhail Zaidenberg\, Fourier Institute\, Grenoble\, France\n
\n
Abstract: Given complex affine algebraic varieties $X$ and $Y$\, the general \n
Zariski Cancellation Problem asks whether the existence of an isomorphism \n
$X\times\mathbb{C}^n\cong Y\times\mathbb{C}^n$ implies that $X\cong Y$. Or\, \n
in other words\, whether varieties with isomorphic cylinders should be \n
isomorphic. This occurs to be true for affine curves (Abhyankar\, Eakin\, and \n
Heinzer $'72$) and false for affine surfaces (Danielewski $'89$). The \n
special Zariski Cancellation Problem asks the same question provided that \n
$Y=\mathbb{C}^k$. In this case\, the answer is "yes" in dimension $k=2$ \n
(Miyanishi-Sugie $'80$ and Fujita $'79$)\, and unknown in higher dimensions\, \n
where the situation occurs to be quite mysterious (indeed\, over a field of \n
positive characteristic\, there is a recent counter-example due to Neena Gupta \n
$'14$). The birational counterpart of the special Zariski Cancellation \n
Problem asks whether stable rationality implies rationality. The answer \n
occurs to be negative\; the first counter-example was constructed by \n
Beauville\, Colliot-Th\'el\`ene\, Sansuc\, and Swinnerton-Dyer $'85$. We will \n
survey on the subject\, both on some classical results and on a very recent \n
development\, reporting in particular on a joint work with Hubert Flenner \n
and Shulim Kaliman.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1568:field_when:0:185
SUMMARY:Bounded approximation and radial interpolation in the unit disc and related \n
questions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150518T150500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150518T160500
URL;VALUE=URI:http://math.biu.ac.il/node/1568
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. A. Danielyan\, University of South Florida\, Tampa\, USA\n
\n
Abstract: The talk is devoted to some bounded approximation and interpolation \n
problems and theorems in the unit disc related to the work of P. Fatou\, W. \n
Rudin\, L. Carleson\, L. Zalcman\, and other authors. Among other results\, a new \n
theorem due to S. Gardiner on radial interpolation will be presented. We also \n
show that the classical Rudin-Carleson interpolation theorem is a simple \n
corollary of Fatou's much older interpolation theorem (of 1906).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1567:field_when:0:186
SUMMARY:Criteria for the Poincare-Hardy inequalities
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150518T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150518T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1567
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. V. Maz'ya\, University of Liverpool and University of \n
Linkoeping\n
\n
Abstract: A number of topics in the qualitative spectral analysis of the \n
Schr\"odinger operator $-\Delta + V$ are surveyed. In particular\, results \n
concerning the positivity and semiboundedness of this operator. The attention \n
is focused on conditions both necessary and sufficient\, as well as on their \n
sharp corollaries.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1566:field_when:0:187
SUMMARY:Gegenbauer-Chebyshev Integrals and Radon Transforms
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150504T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150504T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1566
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. B. Rubin\, Louisiana State University\, Baton Rouge\, USA\n
\n
Abstract: The Radon transform $R$ assigns to a function $f$ on $R^n$ a \n
collection of integrals of that function over hyperplanes in $R^n$. \n
Suppose that $Rf$ vanishes on all hyperplanes that do not meet a fixed \n
convex set. {\it Does it follow that $f$ is zero in the exterior of that \n
set?} I am planning to discuss new results related to this question and the \n
corresponding injectivity problems. If time allows\, some projectively \n
equivalent modifications of $R$ will be considered.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1565:field_when:0:188
SUMMARY:Infinitesimal Hilbert 16th problem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150420T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150420T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1565
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. S. Yakovenko\, Weizmann Institute\n
\n
Abstract: I will describe the current state of affairs in both the original \n
Hilbert 16th problem (on limit cycles of polynomial planar vector fields) \n
and its relaxed version on zeros of Abelian integrals. It turns out that \n
the latter belong to a natural class of Q-functions described by integrable \n
systems of linear differential equations with quasiunipotent monodromy\, \n
defined over the field of rational numbers. Functions of this class admit \n
explicit (albeit very excessive) bounds for the number of their isolated \n
zeros in a way similar to algebraic functions. This result lies at the core \n
of the solution of the infinitesimal Hilbert problem\, achieved with Gal \n
Binyamini and Dmitry Novikov. The talk is aimed at a broad audience.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1564:field_when:0:189
SUMMARY:The Askey-Wilson Algebra
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150603T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150603T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1564
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Hau-Wen Huang (Hebrew University of Jerusalem)\n
\n
Abstract:\n
Motivated by the Racah coefficients\, the Askey-Wilson algebra was introduced \n
by the theoretical physicist Zhedanov. The algebra is named after Richard \n
Askey and James Wilson because this algebra also presents the hidden symmetry \n
between the three-term recurrence relation and $q$-difference equation of the \n
Askey-Wilson polynomials. In this talk\, I will present the progression on the \n
finite-dimensional irreducible modules for Askey-Wilson algebra.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1563:field_when:0:190
SUMMARY:Discovering biological functions of RNA structures in silico: new answers to \n
old questions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150526T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150526T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1563
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Alex Schneider\, CureLab\n
\n
Abstract:\n
RNA is a two-level language. The first level is the language \n
of RNA sequence. The second level is the RNA structures and their \n
biological roles. The seminar will discuss new computational approaches to \n
study the roles RNA structures may play controlling gene expression \n
level\, temperature adaptation\, bacterial and viral evolution.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1561:field_when:0:191
SUMMARY:From groups to clusters
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150527T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150527T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1561
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Sefi Ladkani (Ben-Gurion University)\n
\n
Abstract:\n
I will present a new combinatorial construction of finite-dimensional \n
algebras with some interesting representation-theoretic properties: they are \n
of tame representation type\, symmetric and have periodic modules. The quivers \n
we consider are dual to ribbon graphs and they naturally arise from \n
triangulations of oriented surfaces with marked points.\n
\n
The class of algebras that we get contains in particular the algebras of \n
quaternion type introduced and studied by Erdmann with relation to certain \n
blocks of group algebras. On the other hand\, it contains also the Jacobian \n
algebras of the quivers with potentials associated by Fomin-Shapiro-Thurston \n
and Labardini to triangulations of closed surfaces with punctures. Hence our \n
construction may serve as a bridge between modular representation theory of \n
finite groups and cluster algebras.\n
\n
All notions will be explained during the talk.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1560:field_when:0:192
SUMMARY:On the exponent of the Schur multiplier
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150520T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150520T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1560
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Nicola Sambonet (Technion)\n
\n
Abstract:\n
The Schur multiplier is a very interesting invariant\, being the archetype of \n
group cohomology.\n
An explicit description of the multiplier is often too difficult a task. \n
Therefore it is of interest to obtain information about its arithmetical \n
features\, such as the order\, the rank\, and the exponent.\n
I will present the problem of bounding the exponent of the multiplier of a \n
finite group\, introducing the new concept of unitary cover.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1559:field_when:0:193
SUMMARY:The Borodin-Olshanski Problem and Determinantal Point Processes.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150510T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150510T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1559
LOCATION:seminar room
DESCRIPTION:Speaker: Alexander I. Bufetov (CNRS\, Steklov\, IITP\, NRU-HSE)\n
\n
Abstract:\n
Let mu_{m\,n} be the canonical invariant measure on the Grassmann manifold\n
of m-dimensional subspaces in C^{m+n}\; the flat coordinates on the Grassmann\n
manifold allow us to consider mu_{m\,n} as a measure on the space Mat(m x n) \n
of\n
complex matrices. By definition\, the family of measures mu_{m\,n} has\n
the property of consistency under natural projections\n
Mat((m + 1) n) ---> Mat(m n) \; Mat(m x (n + 1)) ---> Mat(m x n)\n
and consequently defines a probability measure on the space Mat of infinite\n
complex matrices. The measure mu is by definition unitarily-invariant and \n
admits\n
a natural one-parameter family of unitarily-invariant deformations mu^(s)\, \n
called\n
the Pickrell measures. The Pickrell measures are finite for s > -1 and \n
infinite\n
for s < 0.\n
\n
The first main result of the talk is the solution to the problem\, posed by\n
Borodin and Olshanski in 2000\, of the explicit description of the ergodic \n
decomposition of infinite Pickrell measures. The decomposing measures are \n
naturally identified with sigma-finite processes on the half-line R+ and can \n
be viewed as sigma-finite analogues of determinantal point processes. For \n
different values of the parameter s\, these measures are mutually singular.\n
\n
In the second part of the talk we will discuss absolute continuity and \n
singularity of determinantal point processes. The main result here is that \n
determinantal point processes on Z induced by integrable kernels are indeed \n
quasi-invariant under the action of the in nite symmetric group. The \n
Radon-Nikodym derivative is found explicitly. A key example is the discrete \n
sine-process of Borodin\, Okounkov and Olshanski. This result has a continuous \n
counterpart: namely\, that\n
determinantal point processes with integrable kernels on R\, a class that \n
includes processes arising in random matrix theory such as the sine-process\, \n
the process with the Bessel kernel or the Airy kernel\, are quasi-invariant \n
under the action of the group of di eomorphisms with compact support.\n
\n
The first part of the talk is based on the preprint \n
http://arxiv.org/abs/1312.3161 [1]\;\n
the second part\, on the preprint http://arxiv.org/abs/1409.2068 [2].\n
\n
\n
[1] http://arxiv.org/abs/1312.3161\n
[2] http://arxiv.org/abs/1409.2068
END:VEVENT
BEGIN:VEVENT
UID:calendar:1558:field_when:0:194
SUMMARY:Geometry of symplectic transformations: 25 years after
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150503T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150503T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1558
LOCATION:seminar room
DESCRIPTION:Speaker: Leonid Polterovich (Tel-Aviv University)\n
\n
Abstract:\n
In 1990 Helmut Hofer introduced a bi-invariant metric on symplectomorphism\n
groups which nowadays plays an important role in symplectic topology and \n
Hamiltonian dynamics.\n
I will review some old\, new and yet unproved results in this direction.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1557:field_when:0:195
SUMMARY:Free profinite subgroups and Galois representations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150506T111500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150506T121500
URL;VALUE=URI:http://math.biu.ac.il/node/1557
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Mark Shusterman (Tel Aviv University)\n
\n
Abstract: The talk is going to be about the work carried out as part of my \n
MSc thesis. Motivated by recent arithmetic results\, we will consider new \n
and improved results on the freeness of subgroups of free profinite groups: \n
1.The Intermediate Subgroup Theorem - A subgroup (of infinite index) in a \n
nonabelian finitely generated free profinite group\, is contained in a free \n
profinite group of infinite rank. 2. The Verbal Subgroup Theorem - A \n
subgroup containing the normal closure of a (finite) word in the elements of \n
a basis for a free profinite group\, is free profinite. These results shed \n
light on several theorems in Field Arithmetic and may be combined with the \n
twisted wreath product approach of Haran\, an observation on the action of \n
compact groups\, and a rank counting argument to prove a generalization of a \n
result of Bary-Soroker\, Fehm\, and Wiese on the profinite freeness of \n
subgroups arising from Galois representations.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1556:field_when:0:196
SUMMARY:Elliptic curves with maximal Galois action on torsion points
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150513T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150513T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1556
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: David Corwin (Massachusetts Institute of Technology)\n
\n
Abstract: Let E be an elliptic curve over a number field K with algebraic \n
closure K'. For an integer n\, the set of n-torsion points in E(K') forms a \n
group isomorphic to Z/n X Z/n\, which carries an action of G_K=Gal(K'/K). A \n
result of Serre shows that if K=Q\, then the associated homomorphism from G_K \n
to GL_2(Z/n) cannot be surjective for all n. The result is false\, however\, \n
over other number fields. The 2010 PhD thesis of Greicius found the first \n
counterexample\, over a very special non-Galois cubic extension of Q. In \n
this talk I will describe the above background and then describe more recent \n
results of the speaker and others allowing one to find such elliptic curves \n
over a more general class of number fields. As time allows\, I may describe \n
other results from our paper about finding elliptic curves with maximal (but \n
not surjective) Galois action given certain constraints\, or a forthcoming \n
paper doing similar work for abelian surfaces.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1555:field_when:0:197
SUMMARY:Non-commutative graded algebras with restricted growth
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150506T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150506T111500
URL;VALUE=URI:http://math.biu.ac.il/node/1555
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Beeri Greenfeld (Bar-Ilan University)\n
\n
Abstract: Graded algebras play a major role in many topics\, including \n
algebraic geometry\, topology\, and homological algebra\, besides classical ring \n
theory. These are algebras which admit a decomposition into a sum of \n
homogeneous components which 'behave well' with respect to multiplication. In \n
this talk we present several structure-theoretic results concerning affine \n
(that is\, finitely generated) Z-graded algebras which grow 'not too fast'. In \n
particular\, we bound the classical Krull dimension both for algebras with \n
quadratic growth and for domains with cubic growth\, which live in the heart \n
of Artin's proposed classification of non-commutative projective surfaces. We \n
also prove a dichotomy result between primitive and PI-algebras\, relating a \n
graded version of a question of Small. From a radical-theoretic point of \n
view\, we prove that unless a graded affine algebra has infinitely many zero \n
homogeneous components\, its Jacobson radical vanishes. Under a suitable \n
growth restriction\, we prove a stability result for graded Brown-McCoy \n
radicals of Koethe conjecture type: they remain Brown-McCoy even after being \n
tensored with some arbitrary algebra. Finally\, we pose several open questions \n
which could be seen as graded versions of the Kurosh and Koethe conjectures. \n
The talk is based on joint work with A. Leroy\, A. Smoktunowicz and M. \n
Ziembowski.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1553:field_when:0:198
SUMMARY:Higher Structures
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150426T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150426T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1553
LOCATION:seminar room
DESCRIPTION:Speaker: Martin Markl (Academy of Sciences of the Czech Republic)\n
\n
Abstract:\n
Although higher structures have been around for quite some time\, they \n
recently have come back into focus through renewed interest in higher \n
categories. There are several reasons for this.\n
\n
In geometry one is trying to interpret extended cobordism theories\, where the \n
higher structures are meant to mimic higher codimensions. An analogue in \n
algebra is known to the 2-categorical level\, the prime example being the \n
2-category of rings\, bi-modules and bi-module morphisms. Beyond this there \n
are many open questions of fundamental nature. The central problem is what \n
type of coherence to require.\n
\n
In physics higher structures naturally appear in two related fashions. The \n
first is through the extended field theories and the second through field \n
theories with defects. This is mathematically mimicked by cobordisms and \n
defect lines and points abstractly interpreted as inclusions into higher \n
dimensional objects.\n
\n
The "truncated" versions of higher structures can be assembled into infinity \n
up to a homotopy everything version. This is the setting of the influential \n
program of Lurie which provides firm foundations to derived algebraic \n
geometry\, and\, hopefully\, to higher differential geometry which is not yet \n
that well established.\n
\n
Geometric and physical points of view combine in the constructions of string \n
topology and in the proofs of the cobordism hypothesis. One approach to this\, \n
which will also be an integral part of this program\, is the operadic/monadic \n
point of view as many liigher categorical structures can be interpreted as \n
actions of certain liigher dimensional operads/monads. The classical homotopy \n
theory teaches us that this is the correct way to encode higher homotopies \n
and homotopical algebra in general.\n
\n
The complexity of higher dimensional structures and necessity to work with \n
them efficiently has required reconsideration of the foundations of \n
mathematics. A new theory called univalent foundations or homotopy type \n
theory emerges in recent years which has a potential to become a common \n
language for mathematicians working with higher categorical structures. We \n
wish to include this theory as a supplement to our main topics\, but also as a \n
possible future direction of research.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1552:field_when:0:199
SUMMARY:Analysis of Regenerative Heat Exchanger for Microturbine
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150426T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150426T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1552
LOCATION:Seminar Room\, Room 201\, Building 216
DESCRIPTION:Speaker: Gad Pinhasi - Ariel\n
\n
Abstract:\n
A “regenerator” is a special purpose counter-flow heat exchanger used to \n
recover waste heat from exhaust gases. In such heat exchangers the energy \n
storage medium is alternately heated by hot combustion products and cooled by \n
the air supplied to the combustion chamber. This type of heat exchanger can \n
have a thermal efficiency of over 90%\, transferring almost all the relative \n
heat energy from one flow direction to the other. The study is aimed at the \n
development of an efficient regenerative system for gas turbine engines. The \n
proposed design is based on static chambers regenerator with porous ceramic \n
foam as heat transfer/storage media. A numerical model was developed for \n
theoretical analysis and identification of the parameters controlling the \n
performance of a regenerator. The pressure drop and the heat transfer \n
efficiency were calculated and compared for two porous media types: foam type \n
and squared honeycomb.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1551:field_when:0:200
SUMMARY:The Hasse principle for bilinear symmetric forms over the ring of integers of \n
a global function field
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150429T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150429T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1551
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Rony Bitan (Bar-Ilan University)\n
\n
Abstract: Let C be a smooth projective curve defined over a finite field F_q \n
(q is odd)\, and let K=F_q(C) be its (global) function field. This field is \n
considered as the geometric analogue of a number field. Removing one \n
closed point from C results in an affine curve C^af. The ring of regular \n
functions over C^af is an integral domain\, over which we consider a \n
non-degenerate bilinear and symmetric form f of any rank n. We express \n
the number c(f) of isomorphism classes in the genus of f in cohomological \n
terms and use it to present a sufficient and necessary condition depending \n
only on C^af\, under which f admits the Hasse local-global principle. We say \n
that f admits the Hasse local-global principle if c(f)=1\, namely\, \n
|Pic(C^\af)| is odd for any n other than 2 and equal to 1 for n=2. This \n
result emphasizes the difference between Galois cohomology and etale \n
cohomology. Examples are provided.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1549:field_when:0:201
SUMMARY:On the Cerny conjecture
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150419T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150419T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1549
LOCATION:Seminar room
DESCRIPTION:Speaker: Andrzej Kisielewicz (Wroclaw)\n
\n
Abstract:\n
The Cerny conjecture\, concerned with the minimal length of a reset word in a \n
finite automata\, is considered one of the most longstanding open problem in \n
the theory of finite automata. In this talk\, we discuss the \n
background of the conjecture\, attempts at a proof\, and partial results \n
obtained so far by various researchers. In the second part\, we present our \n
recent results\, which shade a light on the question of why the conjecture is \n
so hard to prove.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1548:field_when:0:202
SUMMARY:On summability methods for Fourier series and Fourier integrals
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150413T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150413T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1548
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. R. Trigub\, Donetsk National University\, Ukraine\n
\n
Abstract:\n
In the problem of summability at a point at which the derivative of \n
indefinite\n
integral exists for Fourier series and Fourier integrals of integrable \n
functions\n
a new sufficient condition is obtained. In the case of "arithmetic means" the\n
corresponding condition is also necessary.\n
Exact rates of approximation by the classical Gauss-Weierstrass\, \n
Bochner-Riesz\,\n
and Marcinkiewicz-Riesz means\, as well as by non-classical Bernstein-Stechkin \n
means\n
are found.\n
These problems are related to the representability of a function as an \n
absolutely\n
convergent Fourier integral. For this\, new conditions are obtained\, while for \n
radial functions\n
even a criterion.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1546:field_when:0:203
SUMMARY:Rationally isomorphic quadratic objects
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150415T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150415T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1546
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Uriya First (University of British Columbia)\n
\n
Abstract: Let R be a discrete valuation ring with fraction field F. Two \n
algebraic objects (say\, quadratic forms) defined over R are said to be \n
rationally isomorphic if they become isomorphic after extending scalars to F. \n
In the case of unimodular quadratic forms\, it is a classical result that \n
rational isomorphism is equivalent to isomorphism. This has been recently \n
extended to "almost umimodular" forms by Auel\, Parimala and Suresh. I will \n
present further generalizations to hermitian forms over (certain) involutary \n
R-algebras and quadratic spaces equipped with a group action ("G-forms"). The \n
results can be regarded as versions of the Grothendieck-Serre conjecture for \n
certain /non-reductive/ groups. (Joint work with Eva Bayer-Fluckiger.)
END:VEVENT
BEGIN:VEVENT
UID:calendar:1526:field_when:0:204
SUMMARY:Putting a diamond inside the square
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150125T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150125T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1526
LOCATION:seminar room
DESCRIPTION:Speaker: Assaf Rinot\n
\n
Abstract:\n
Gray's combinatorial principle SD_k is a strong combination of Jensen [1]'s \n
Square_k [2] and Diamond(k^+) [3] principles. This principle proved itself \n
very useful in constructing uncountable graphs of counter-intuitive nature \n
[4].\n
\n
By a 35 year old theorem of Shelah [5]\, Square_k+Diamond(k^+) does not imply \n
SD_k for regular uncountable cardinals k. In this talk\, I will prove that \n
they are equivalent whenever k is singular.\n
\n
\n
\n
Bibliography [6]\n
\n
\n
[1] https://en.wikipedia.org/wiki/Ronald_Jensen\n
[2] https://en.wikipedia.org/wiki/Square_principle\n
[3] https://en.wikipedia.org/wiki/Diamond_principle\n
[4] http://www.assafrinot.com/paper/16\n
[5] https://en.wikipedia.org/wiki/Saharon_Shelah\n
[6] http://www.assafrinot.com/paper/19
END:VEVENT
BEGIN:VEVENT
UID:calendar:1543:field_when:0:205
SUMMARY:Everything is Illuminated (Except for at Most Finitely Many Points)
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150322T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150322T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1543
LOCATION:Department room
DESCRIPTION:Speaker: Barak Weiss (TAU)\n
\n
Abstract:\n
Suppose a light source is placed in a polygonal hall of mirrors (so light can \n
bounce off the walls). Does every point in the room get illuminated? This \n
elementary geometrical question was open from the 1950s until Tokarsky (1995) \n
found an example of a polygonal room in which there are two points which do \n
not illuminate each other. Resolving a conjecture of \n
Hubert-Schmoll-Troubetzkoy\, in joint work with Lelievre and Monteil we prove \n
that if the angles between walls is rational\, every point illuminates all but \n
at most finitely many other points. The proof is based on recent work by \n
Eskin\, Mirzakhani and Mohammadi in the ergodic theory of the SL(2\,R) action \n
on the moduli space of translation surfaces. The talk will serve as a gentle \n
introduction to the amazing results of Eskin\, Mirzakhani and Mohammadi.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1542:field_when:0:206
SUMMARY:On the Teichmüller map and a class of nonassociative algebras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150325T111500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150325T121500
URL;VALUE=URI:http://math.biu.ac.il/node/1542
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Darrell Haile (Indiana University)\n
\n
Abstract:\n
This is joint work with Yuval Ginosar. Let K/F be a finite Galois extension \n
with Galois group G. The Teichmüller map is a function that associates to \n
every central simple K-algebra B normal over F an element of H^3(G\, K*). \n
The value of the function is trivial precisely when the class of B is \n
restricted from F. The classical definition of this map involves the use of \n
a crossed-product algebra over B. The associativity of this algebra is also \n
equivalent to the class of B being restricted from F. The aim of this \n
lecture is to elucidate the nature of the nonassociative algebras that arise \n
when B is normal but not restricted. It turns out that the resulting theory \n
is remarkably similar to the theory of associative algebras arising from the \n
noninvertible cohomology of a Galois extension L/F such that L contains K\, \n
and I want to explain that relationship.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1541:field_when:0:207
SUMMARY:Some remarks on tilting theory
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150325T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150325T111500
URL;VALUE=URI:http://math.biu.ac.il/node/1541
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Gabriella D'Este (University of Milan)\n
\n
Abstract:\n
In the first part of my talk I will describe with few words and many pictures \n
some more or less ‘combinatorial’ results on tilting modules\, bimodules \n
and complexes\, almost always obtained by means of elementary tools of two \n
types:\n
\n
\n
\n
- Linear Algebra arguments (that is\, comparison of the dimensions of the \n
underlying vector spaces of certain \n
\n
Hom and Ext groups)\;\n
\n
\n
\n
- Representation Theory arguments (that is\, analysis of the Auslander - \n
Reiten quivers of suitable finite dimensional algebras\, almost always \n
admitting only finitely many indecomposable modules up to isomorphism). \n
\n
\n
\n
In the second part of my talk I will describe other results (suggested by \n
quivers) concerning ‘reflexive’ modules (not necessarity belonging to \n
the tilting and cotilting worlds) and multiplicities of simple modules in the \n
socle of certain injective cogenerators. Almost all the results and \n
examples are illustrated in two preprints available at \n
\n
http://arxiv.org/abs/1401.2085 [1] and \n
\n
http://arxiv.org/abs/1411.4418 [2] . \n
\n
\n
[1] http://arxiv.org/abs/1401.2085\n
[2] http://arxiv.org/abs/1411.4418
END:VEVENT
BEGIN:VEVENT
UID:calendar:1539:field_when:0:208
SUMMARY:Coherent omission of intervals: Menger's and Hurewicz's problems
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150315T140500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150315T151500
URL;VALUE=URI:http://math.biu.ac.il/node/1539
LOCATION:Department room
DESCRIPTION:Speaker: Piotr Szewczak (BIU and Cardinal Stefan Wyszyński University\, \n
Warsaw)\n
\n
Abstract:\n
We introduce Menger and Hurewicz covering properties\, which are \n
generalizations of sigma-compactness. Menger and Hurewicz conjectured that\, \n
for subsets of the real line\, the above properties were equivalent to \n
sigma-compactness. Using topological and an elegant combinatorial method \n
(coherent omission of intervals)\, we show (in ZFC) that they are false. We \n
consider also stronger covering properties\, relations between them and we \n
give examples of such sets of reals. After that we obtain the solution to the \n
Hurewicz problem: Is there in ZFC an example of set of reals which is Menger \n
but not Hurewicz? Finally we show some results concerning behavior of Menger \n
and Hurewicz properties in finite products.\n
\n
\n
\n
The methods\, proofs\, and results\, are mainly due to Tsaban and his \n
collaborators. The last lecture will include new results\, due to Tsaban and \n
the speaker.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1538:field_when:0:209
SUMMARY:Some facts about the Gieseking group
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150318T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150318T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1538
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Moshe Newman\n
\n
Abstract:\n
The Gieseking group is a one-relator group defined by the\n
equation aab=bba. It is also the fundamental group of a certain\n
3-dimensional manifold. As a non-topologist trying to make use of the\n
latter fact\, I learned some things the hard way\, which I will share\n
with the audience.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1537:field_when:0:210
SUMMARY:Non-Archimedean analytic geometry
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150315T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150315T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1537
LOCATION:Department room
DESCRIPTION:Speaker: Valdimir Berkovich\n
\n
Abstract:\n
Non-Archimedean analytic geometry is an analog of complex analytic geometry \n
over non-Archimedean (e.g.\, p-adic) fields. In the talk\, I'll explain what \n
non-Archimedean analytic spaces are\, list basic facts about them\, and tell \n
about their applications
END:VEVENT
BEGIN:VEVENT
UID:calendar:1536:field_when:0:211
SUMMARY:A new analysis of two proximal forward-backward algorithms with and without \n
errors
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150315T105500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150315T115500
URL;VALUE=URI:http://math.biu.ac.il/node/1536
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Daniel Reem - ICMC\, University of Sao Paulo\n
\n
Abstract:\n
Many problems in science and engineering involve\, as part of their solution \n
process\, the consideration of a minimization of a composite function F=f+g \n
where f is smooth\, g possibly not\, and both are convex. The talk will \n
discuss\, in generalized settings\, two proximal forward-backward algorithms \n
aiming at solving this task. The first is FISTA\, a \n
popular accelerated method suggested by Beck-Teboulle. We consider it in \n
Hilbert spaces and allow error terms which satisfy a certain decay rate. \n
The notion of inexactness we discuss seems to be simpler than the ones \n
discussed in related works but\, interestingly\, very similar decay rates \n
of the error terms yield very similar non-asymptotic convergence rates (in \n
the function values). Our derivation also sheds some light on the somewhat \n
mysterious origin of some relevant parameters. In the second method\, which \n
is non-accelerated\, the setting is closed and convex subsets of reflexive \n
Banach spaces where the proximal operation is based on a (strongly convex) \n
Bregman divergence. Now\, in contrast to previous works\, the gradient of f \n
may not be globally Lipschitz continuous. Under certain assumptions a \n
non-asymptotic rate of convergence is established\, as well as weak \n
convergence of the whole sequence.\n
\n
This is a joint work with Alvaro De Pierro
END:VEVENT
BEGIN:VEVENT
UID:calendar:1535:field_when:0:212
SUMMARY:Stringy Chern classes of toric varieties and their applications
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150311T111500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150311T121500
URL;VALUE=URI:http://math.biu.ac.il/node/1535
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Victor Batyrev (Universität Tübingen)\n
\n
Abstract:\n
Stringy Chern classes of singular projective algebraic varieties can be\n
defined by some explicit formulas using a resolution of singularities. It is \n
important that the output of these formulas does not depend on the choice of \n
a resolution.\n
The proof of this independence is based on nonarchimedean motivic \n
integration.\n
The purpose of the talk is to explain a combinatorial computation of stringy \n
Chern\n
classes for singular toric varieties. As an application one obtains\n
combinatorial formulas for the intersection numbers of stringy Chern classes\n
with toric Cartier divisors and some interesting combinatorial identities for \n
convex lattice polytopes.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1534:field_when:0:213
SUMMARY:Real Galois cohomology of simply connected groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150311T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150311T111500
URL;VALUE=URI:http://math.biu.ac.il/node/1534
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Mikhail Borovoi (Tel Aviv University)\n
\n
Abstract:\n
By the celebrated Hasse principle of Kneser\, Harder and Chernousov\,\n
calculating the Galois cohomology H^1(K\,G) of a simply connected simple\n
K-group over a number field K reduces to calculating H^1(R\,G) over the\n
field of real numbers R. For some cases\, in particular\, for the split\n
simply connected R-group G of type E_7\, the first calculations of\n
H^1(R\,G) appeared only in 2013 and 2014 in preprints of Jeffry Adams\,\n
of Brian Conrad\, and of the speaker and Zachi Evenor. All these\n
calculations used the speaker's note of 1988.\n
In the talk I will explain the method of Kac diagrams of calculating\n
H^1(R\,G) for a simply connected simple R-group G by the examples of\n
groups of type E_7. The talk is based on a work in progress with\n
Dmitry A. Timashev. No preliminary knowledge of Galois cohomology or\n
of groups of type E_7 is assumed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1533:field_when:0:214
SUMMARY:The Positive Mass Theorem for Multiple Rotating Charged Black Holes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150308T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150308T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1533
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Gilbert Weinstein - Ariel\n
\n
Abstract:\n
In this talk I will present a lower bound for the ADM mass given in terms\n
of the angular momenta and charges of black holes present in axisymmetric\n
initial data sets for the Einstein-Maxwell equations. This generalizes the\n
mass-angular momentum-charge inequality obtained by Chrusciel and Costa to\n
the case of multiple black holes. We also weaken the hypotheses used in the\n
proof of this result for single black holes\, and establish the associated\n
rigidity statement. The proof uses an existence result for harmonic maps\n
with prescribed singularities.\n
This is joint work with Marcus Khuri\n
http://arxiv.org/abs/1502.06290 [1]\n
\n
\n
\n
[1] http://arxiv.org/abs/1502.06290
END:VEVENT
BEGIN:VEVENT
UID:calendar:1532:field_when:0:215
SUMMARY:HÖLDER CONDITIONS FOR ENDOMORPHISMS OF HYPERBOLIC GROUPS
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150308T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150308T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1532
LOCATION:Seminar Room\, Dept. of Mathematics\, Bar-Ilan University
DESCRIPTION:Speaker: Pedro V. Silva (University of Porto)\n
\n
Abstract:\n
Hyperbolic groups can be defined through the geometry of Cayley graphs\, \n
viewed as geodesic metric spaces. One important feature of hyperbolic groups \n
is the concept of boundary\, which can be defined through the topological \n
completion for an appropriate metric (such as the visual metrics)\, and has \n
the advantages of compactness. An endomorphism of a hyperbolic group admits a \n
continuous extension to the boundary if and only if it is uniformly \n
continuous with respect to a visual metric\, and a Hölder condition is a \n
particularly nice way of achieving uniform continuity. In joint work with \n
Vítor Araújo (Universidade Federal da Bahia)\, we have proved that an \n
endomorphism of a hyperbolic group satisfies a Hölder condition with respect \n
to a visual metric if and only if it is virtually injective and its image is \n
a quasi-convex subgroup. Moreover\, if the group is virtually free or \n
torsion-free co-hopfian\, then the endomorphism is uniformly continuous if and \n
only if it satisfies a Hölder condition if and only if it is virtually \n
injective. However\, this stronger claim does not necessarily hold for \n
arbitrary hyperbolic groups.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1525:field_when:0:216
SUMMARY:Periodic groups and their automorphisms
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150125T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150125T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1525
LOCATION:seminar room
DESCRIPTION:Speaker: Remi Coulon\n
\n
Abstract: The free Burnside group of exponent n\, B(r\,n)\, is the quotient of \n
the free group of rank r by the subgroup generated by all n-th powers. This \n
group was introduced in 1902 by W. Burnside who asked whether it is finite or \n
not. This problem motivated many developments in group theory. In 1968 P.S. \n
Novikov and S.I. Adian made a breakthrough by proving that if n is \n
sufficiently large then B(r\,n) is infinite. In this talk we will focus on the \n
symmetries of B(r\,n). More precisely we will consider on the outer \n
automomorphism group of B(r\,n). Among other things\, we will see that it \n
inherits some properties coming from the outer automorphism group of free \n
groups.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1524:field_when:0:217
SUMMARY:Decidability vs. undecidability for the word problem in amalgams of inverse \n
semigroups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150128T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150128T111500
URL;VALUE=URI:http://math.biu.ac.il/node/1524
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Prof. Alessandra Cherubini (Politecnico di Milano)\n
\n
Abstract:\n
In 2012 J. Meakin posed the following question: under what conditions is the \n
word problem for amalgamated free products of inverse semigroups decidable?\n
\n
Some positive results were interrupted by a result of Radaro and Silva \n
showing that the problem is undecidable even under some nice conditions. \n
Revisiting the proofs of decidability\, we discuss whether positive \n
results can be achieved for wider classes of inverse semigroups and show how \n
small the distance is between decidability and undecidability.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1522:field_when:0:218
SUMMARY:Martin's Axiom\, and a strengthening of the Dushnik-Miller partition relation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150118T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150118T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1522
LOCATION:seminar room
DESCRIPTION:Speaker: Dani Livne\n
\n
Abstract:\n
Bibliography [1]\n
\n
\n
[1] http://www.essex.ac.uk/maths/people/fremlin/psfr84.ps
END:VEVENT
BEGIN:VEVENT
UID:calendar:1523:field_when:0:219
SUMMARY:Fluctuations-induced coexistence in public goods dynamics
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150118T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150118T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1523
LOCATION:seminar room
DESCRIPTION:Speaker: Yoram Luzon\n
\n
Abstract:\n
Cooperative interactions\, their stability and evolution\, provide an \n
interesting context in which to study the interface between cellular and \n
population levels of organization. Such interactions also open the way for \n
the discovery of new population dynamics mechanisms.\n
\n
We have studied a version of the public goods model relevant to microorganism \n
populations actively extracting a growth resource from their environment. \n
Cells can display one of two phenotypes – a productive phenotype that \n
extracts the resources at a cost\, and a non-productive phenotype that only \n
consumes the same resource. We analyze the continuous differential equation \n
model as well as simulate stochastically the full dynamics. It is found that \n
the two sub-populations\, which cannot coexist in a well-mixed environment\, \n
develop spatio-temporal patterns that enable long-term coexistence in the \n
shared environment. These patterns are solely fluctuation-driven\, since the \n
continuous system does not display Turing instability. The average stability \n
of the coexistence patterns derives from a dynamic mechanism in which one \n
sub-population holds the environmental resource close to an extinction \n
transition of the other\, causing it to constantly hover around its critical \n
transition point\, forming a mechanism reminiscent of selforganized \n
criticality. Accordingly\, power-law distributions and long-range correlations \n
are found.\n
\n
When a time scale separation occurs between two dynamic parameters is \n
defined\, a structurally unstable point emerges and any small perturbation of \n
the dynamics with additive noise leads to an equilibrium distribution in \n
which both species coexist in context of additive but not multiplicative \n
noise.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1520:field_when:0:220
SUMMARY:Pro-isomorphic zeta functions of groups and solutions to congruence equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150128T111500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150128T121500
URL;VALUE=URI:http://math.biu.ac.il/node/1520
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Mark Berman (ORT Braude College of Engineering)\n
\n
Abstract:\n
Zeta functions of groups were introduced by Grunewald\, Segal and Smith in \n
1988. They have proved to be a powerful tool for studying the subgroup \n
structure and growth of certain groups\, especially finitely generated \n
nilpotent groups. Three types of zeta function have received special \n
attention: those enumerating all subgroups\, normal subgroups or \n
"pro-isomorphic" subgroups: subgroups isomorphic to the original group after \n
taking profinite completions. Of particular interest is a striking symmetry \n
observed in many explicit computations\, of a functional equation for local \n
factors of the zeta functions. Inspired by wide-reaching results\, due to \n
Voll\, for the first two types of zeta function\, I will talk about recent \n
progress on the functional equation for local pro-isomorphic zeta functions. \n
Thanks to work of Igusa and of du Sautoy and Lubotzky\, these local zeta \n
functions can be analysed by translating them into integrals over certain \n
points of an automorphism group of a Lie algebra associated to the nilpotent \n
group and then applying a p-adic Bruhat decomposition due to Iwahori and \n
Matsumoto. While this technique proves a functional equation for certain \n
classes of such integrals\, it is difficult to relate these results back to \n
the nilpotent groups they arise from. In particular\, it is not known whether \n
the local pro-isomorphic zeta functions of all finitely generated groups of \n
nilpotency class 2 enjoy local functional equations. I will discuss recent \n
explicit calculations of pro-isomorphic zeta functions for specific nilpotent \n
groups. Interesting new features include an example of a group whose local \n
zeta functions do not satisfy functional equations\, a family of groups whose \n
global zeta functions have non-integer abscissae of convergence of arbitrary \n
denominator\, and an example whose calculation requires solving congruence \n
equations modulo p^n for a prime p. The latter sheds new light on the types \n
of automorphism groups that can be expected to arise. This is joint work with \n
Benjamin Klopsch and Uri Onn.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1519:field_when:0:221
SUMMARY:Prime polynomial values of linear functions in short intervals
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150121T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150121T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1519
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Efrat Bank (Tel Aviv University)\n
\n
Abstract:\n
In this talk I will present a function field analogue of a conjecture in \n
number theory. This conjecture is a combination of several famous \n
conjectures\, including the Hardy-Littlewood prime tuple conjecture\, \n
conjectures on the number of primes in arithmetic progressions and in short \n
intervals\, and the Goldbach conjecture. I prove an asymptotic formula for the \n
number of simultaneous prime values of $n$ linear functions\, in the limit of \n
a large finite field.\n
A key role is played by the computation of some Galois groups.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1518:field_when:0:222
SUMMARY:Covering in the Plane
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150118T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150118T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1518
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Shai Gul - BIU\n
\n
Abstract:\n
We consider the problem of efficiently covering a domain by unit discs. This \n
problem has applications in optimal cellular antennae placement\, facility \n
location any many other similar problems. Our main interest is a result by W. \n
Blaschke\, which determines an upper bound to the number of unit discs which \n
are needed to cover a given convex domain . Blaschke showed that a domain can \n
be covered with 2A/3 sqrt(3) + 2L/ pi sqrt(3) + 1 (1) unit circles\, \n
where /A/ is the area of the given domain and /L/ the perimeter. This result \n
is due to the properties of the hexagonal lattice. This talk will be composed \n
of three main results. First\, we will show that in special cases Blaschke's \n
result can be improved and then show how to locate the hexagonal lattice in \n
these cases. Second\, we will give a sufficient condition under which (1) can \n
be improved. Third\, we will give an algorithmic approach which determines the \n
exact position of the hexagonal lattice\, such that the number of unit \n
hexagons (in the hexagonal lattice) which hit the domain is minimized.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1517:field_when:0:223
SUMMARY:Planar Sobolev extension domains and a Square Separation Theorem
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150119T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150119T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1517
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. P. Shvartsman\, Technion\n
\n
Abstract:\n
For each positive integer $m$ and each $p>2$ we characterize bounded simply \n
connected\n
Sobolev $W^m_p$-extension domains $\Omega$ in $R^2$. Our criterion is \n
expressed in terms of\n
certain intrinsic subhyperbolic metrics in $\Omega$. Its proof is based on a \n
series of results related\n
to the existence of special chains of squares joining given points $x$ and \n
$y$ in $\Omega$.\n
\n
An important geometrical ingredient for obtaining these results is a new \n
''Square Separation Theorem''.\n
It states that under certain natural assumptions on the relative positions of \n
a point $x$ and a square\n
$S\subset\Omega$ there exists a similar square $Q\subset\Omega$ which touches \n
$S$ and has\n
the property that $x$ and $S$ belong to distinct connected components of \n
$\Omega\setminus Q$.\n
\n
This is a joint work with Nahum Zobin.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1516:field_when:0:224
SUMMARY:Automorphic equivalence in varieties of representations of Lie algebras
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150114T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150114T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1516
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Arkady Tsurkov (Federal University of Rio Grande do Norte)\n
\n
Abstract:\n
See attached file.\n
\n
http://math.biu.ac.il/files/math/seminars/atsurkov_abst_biu.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:1513:field_when:0:225
SUMMARY:Sign rank\, VC dimension and spectral gaps
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150111T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150111T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1513
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Shay Moran (Technion)\n
\n
Abstract:\n
We study the maximum possible sign rank of $N \times N$ sign matrices with a \n
given VC dimension $d$. For $d=1$\, this maximum is $3$. For $d=2$\, this \n
maximum is $\tilde{\Theta}(N^{1/2})$. Similar (slightly less accurate) \n
statements hold for $d>2$ as well. We discuss the tightness of our methods\, \n
and describe connections to combinatorics\, communication complexity and \n
learning theory.\n
\n
We also provide explicit examples of matrices with low VC dimension and high \n
sign rank. Let $A$ be the $N \times N$ point-hyperplane incidence matrix of \n
a finite projective geometry with order $n \geq 3$ and dimension $d \geq 2$. \n
The VC dimension of $A$ is $d$\, and we prove that its sign rank is larger \n
than $N^{\frac{1}{2}-\frac{1}{2d}}$. The large sign rank of $A$ demonstrates \n
yet another difference between finite and real geometries.\n
\n
To analyze the sign rank of $A$\, we introduce a connection between sign rank \n
and spectral gaps\, which may be of independent interest. Consider the $N \n
\times N$ adjacency matrix of a $\Delta$-regular graph with a second \n
eigenvalue (in absolute value) $\lambda$ and $\Delta \leq N/2$. We show that \n
the sign rank of the signed version of this matrix is at least \n
$\Delta/\lambda$. A similar statement holds for all regular (not necessarily \n
symmetric) sign matrices. We also describe limitations of this approach\, in \n
the spirit of the Alon-Boppana theorem.\n
\n
Joint work with Noga Alon and Amir Yehudayoff.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1510:field_when:0:226
SUMMARY:Nonlinear Equilibrium vs. Linear Programming for resource allocation \n
problems.
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150111T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150111T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1510
LOCATION:seminar room
DESCRIPTION:Speaker: Roman Polyak\n
\n
Abstract:\n
For three quarters of a century Linear Programming (LP) was the main tool \n
for solving resource allocation problems (RAP)- one of the main problem in \n
economics.\n
\n
\n
\n
\n
\n
In 1975 L. V. Kantorovich and T. C. Koopmans shared the Nobel Prize in \n
Economics *Nonlinear Equilibrium vs. Linear Programming for resource \n
allocation problems.*“for their contributions to the theory of optimum \n
allocation of limited resources."\n
\n
When LP is used for RAP the prices for goods and the resource availability \n
are given a priori and independent on the production output and prices for \n
the resources. It often leads to solutions\, which are not practical\, because \n
they contradict to the basic market law of supply and demand.\n
\n
We consider an alternative to LP approach to RAP\, which is based on Nonlinear \n
Equilibrium (NE). The NE is a generalisation of Walras-Wald equilibrium\, \n
which is equivalent to J Nash equilibrium in n-person concave game.\n
\n
NE eliminates the basic drawbacks of LP. Finding NE is equivalent to solving \n
a variation inequality (VI) on the Cartesian product of the primal and dual \n
non negative octants\, projection on which is a very simple operation. For \n
solving the VI we consider two methods: projected pseudo-gradient (PPG) and \n
extra pseudo-gradient (EPG)\, for which projection is the main operation at \n
each step.\n
\n
We established convergence\, proved global Q-linear rate and estimated \n
complexity of both methods under various assumptions on the input data.\n
\n
Both PPG and EPG can be viewed as pricing mechanisms for establishing \n
economic equilibrium.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1509:field_when:0:227
SUMMARY:On Boutroux's Tritronqu\'ee Solutions of the First Painlev\'e Equation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150112T150500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150112T160500
URL;VALUE=URI:http://math.biu.ac.il/node/1509
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Michael Twito\, University of Sydney Australia\n
\n
Abstract:\n
The triply truncated solutions of the first Painlev\'e equation were \n
specified by Boutroux \n
in his famous paper of 1913 as those having no poles (of large modulus) \n
except in one sector \n
of angle $2\pi/5$. There are five such solutions and each of them can be \n
obtained from any \n
other one by applying a certain symmetry transformation. One of these \n
solutions is real on \n
the real axis. We will discuss a characteristic property of this solution \n
(discovered by Prof. \n
Joshi\, and Prof. Kitaev)\, different from the asymptotic description given by \n
Boutroux.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1508:field_when:0:228
SUMMARY:Bernoulli convolution measures and their Fourier transforms
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150112T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150112T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1508
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. B. Solomyak\n
\n
Abstract:\n
For $\lambda\in (0\,1)$\, the Bernoulli convolution measure $\nu_\lambda$ may \n
be defined as the distribution \n
of the random series $\sum_{n=0}^\infty \pm \lambda^n$\, where the signs are \n
chosen independently with equal \n
probabilities. For $\lambda =1/3$\, this is the familiar Cantor-Lebesgue \n
measure (up to a linear change of variable). \n
The Fourier transform of $\nu_\lambda$ has an infinite product formula:\n
$$\widehat{\nu}_\lambda(t) = \prod_{n=0}^\infty \cos(2\pi \lam^n t).$$\n
The properties of $\nu_\lambda$ and their Fourier transforms have been \n
studied since the 1930's by many mathematicians\, \n
among them Jessen\, Wintner\, Erd\H{o}s\, Salem\, Kahane\, Garcia. In particular\, \n
it was proved by Erd\H{o}s and Salem that \n
$\widehat{\nu}_\lambda(t)$ does not vanish at infinity (i.e. $\nu_\lambda$ is \n
not a Rajchman measure) if and only if \n
$1/\lambda$ is a Pisot number (an algebraic integer greater than one with all \n
conjugates inside the unit circle). \n
However\, very little is known about the rate of decay\, especially for \n
specific $\lambda$\, as opposed to "typical" ones. \n
In this talk I will survey known results and open problems in this direction. \n
Recently in a joint work with A. Bufetov \n
we proved that if $1/\lam$ is an algebraic integer with at least one \n
conjugate outside of the unit circle\, then the \n
Fourier transform of $\nu_\lam$ has at least a logarithmic decay rate at \n
infinity.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1507:field_when:0:229
SUMMARY:Around a question of Bonanzinga and Matveev
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150111T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150111T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1507
LOCATION:Seminar room
DESCRIPTION:Speaker: Shir Sivroni\n
\n
Abstract:\n
Which Isbell-Mrowka spaces spaces satisfy the star version of Menger’s \n
covering property?\n
\n
Following Bonanzinga and Matveev\, this question is considered here from a \n
combinatorical point of view. We give an answer to a problem thay have \n
stated\, and present some related open problems.\n
\n
All is taken from this [1] paper by Boaz Tsaban.\n
The slides are available here [2].\n
\n
\n
[1] http://arxiv-web3.library.cornell.edu/pdf/1405.7208v2.pdf\n
[2] https://drive.google.com/viewerng/viewer?a=v&\;pid=sites&\;srcid=ZGVmYXVsdGRvbWFpbnxzaGlyc2l2cm9uaTEyfGd4OjJmNDNhOWE0NGFhMzJiODg
END:VEVENT
BEGIN:VEVENT
UID:calendar:1505:field_when:0:230
SUMMARY:Lie superalgebras\, representations and characters
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150104T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150104T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1505
LOCATION:Seminar Room\, Dept. of Mathematics
DESCRIPTION:Speaker: Shifi Reif\n
\n
Abstract: Lie superalgebras and their representations were introduced to \n
mathematics to study supersymmetry in theoretical physics and have since \n
been applicable in algebra\, combinatroics\, number theory and various other \n
fields. We shall discuss the recently proved Kac-Wakimoto character \n
formula for representations of Lie superalgebras and \n
its specializations to formulas in combinatorics and number theory such \n
as the Jacobi formula for counting the number of presentations of an integer \n
as a sum of k squares.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1504:field_when:0:231
SUMMARY:Reconstruction of the geometric structure of a set of points in the plane \n
from its geometric tree graph
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150104T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150104T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1504
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Chaya Keller (Hebrew University)\n
\n
Abstract: Let $P$ be a finite set of points in general position in the plane. \n
The structure of the complete graph $K(P)$ as a geometric graph includes\, for \n
any pair $[a\,b]\,[c\,d]$ of vertex-disjoint edges\, the information whether they \n
cross or not. The simple (i.e.\, non-crossing) spanning trees (SSTs) of \n
$K(P)$ are the vertices of the so-called Geometric Tree Graph of $P$\, $G(P)$. \n
Two such vertices are adjacent in $G(P)$ if they differ in exactly two edges\, \n
i.e.\, if one can be obtained from the other by deleting an edge and adding \n
another edge. Introduced by Avis and Fukuda in 1993\, geometric tree graphs \n
were studied in a number of papers and play an important role in algorithms \n
for spanning trees enumeration. In this talk we show how to reconstruct \n
from $G(P)$ (regarded as an abstract graph) the structure of $K(P)$ as a \n
geometric graph. This result can be viewed as a geometric counterpart of a \n
work of Sedlacek (1974) on reconstruction of an abstract graph from the list \n
of its spanning trees\, and may shed light on the structure of the \n
automorphism group of $G(P)$ whose determination is a 15-years old open \n
problem. Joint work with Micha A. Perles. Note: The talk will be given \n
in Hebrew.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1503:field_when:0:232
SUMMARY:Zeros of solutions of linear differential equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150105T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20150105T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1503
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Prof. A. Eremenko\, Purdue University\n
\n
Abstract:\n
This is a joint work with Walter Bergweiler.\n
We construct differential equations of the form w"+Aw=0\, where $A$ \n
is an entire function of finite order\, with the property that two \n
linearly independent solutions have finite exponent of convergence \n
of zeros. This solves a problem proposed by Bank and Laine in 1982.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1501:field_when:0:233
SUMMARY:Arrangements of equal minors in the positive Grassmannian
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1501
LOCATION:Building 216\, Room 201
DESCRIPTION:Speaker: Miriam Farber (MIT)\n
\n
Abstract:\n
We discuss arrangements of equal minors in totally positive matrices. More \n
precisely\, we would like to investigate the structure of possible equalities \n
and inequalities between the minors. We show that arrangements of equals \n
minors of largest value are in bijection with sorted sets\, which earlier \n
appeared in the context of alcoved polytopes and Grobner bases. Maximal \n
arrangements of this form correspond to simplices of the \n
alcoved triangulation of the hypersimplex\; and the number of such \n
arrangements equals the Eulerian number. On the other hand\, we conjecture \n
and prove in many cases that arrangements of equal minors of smallest value \n
are exactly the weakly separated sets. Weakly separated sets\, \n
originally introduced by Leclerc and Zelevinsky\, are closely related to \n
the positive Grassmannian and the associated cluster algebra.\n
\n
This is a joint work with Alexander Postnikov.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1500:field_when:0:234
SUMMARY:Arithmetic circuits and algebraic geometry
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141231T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141231T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1500
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Klim Efremenko (University of California\, Berkeley)\n
\n
Abstract:\n
The goal of this talk is to show that natural questions in complexity theory \n
raise very natural questions in algebraic geometry. \n
\n
\n
\n
More precisely\, we will show how to adapt an approach introduced by \n
Landsberg and Ottaviani\, called Young Flattening\, to questions about \n
arithmetic circuits. We will show that this approach generalizes the method \n
of shifted partial derivatives introduced by Kayal to show lower bounds for \n
shallow circuits. \n
\n
We will also show how one can calculate shifted partial derivatives of the \n
permanent using methods from homological algebra\, namely by calculating a \n
minimal free resolution of an ideal generated by partial derivatives.\n
\n
\n
\n
I will not assume any previous knowledge about arithmetic circuits. \n
\n
Joint work with J.M. Landsberg\, H Schenck\, J Weyman.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1499:field_when:0:235
SUMMARY:Arithmetic circuits and algebraic geometry
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141231T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141231T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1499
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Klim Efremenko (University of California\, Berkeley)\n
\n
Abstract:\n
The goal of this talk is to show that natural questions in complexity theory \n
raise very natural questions in algebraic geometry. \n
\n
\n
\n
More precisely\, we will show how to adapt an approach introduced by \n
Landsberg and Ottaviani\, called Young Flattening\, to questions about \n
arithmetic circuits. We will show that this approach generalizes the method \n
of shifted partial derivatives introduced by Kayal to show lower bounds for \n
shallow circuits. \n
\n
We will also show how one can calculate shifted partial derivatives of the \n
permanent using methods from homological algebra\, namely by calculating a \n
minimal free resolution of an ideal generated by partial derivatives.\n
\n
\n
\n
I will not assume any previous knowledge about arithmetic circuits. \n
\n
Joint work with J.M. Landsberg\, H Schenck\, J Weyman.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1498:field_when:0:236
SUMMARY:Hopf Bifurcation in Symmetric Networks of van der Pol Oscillators with \n
Ferromagnetic Core: Twisted Equivariant Degree Approach
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1498
LOCATION:Seminar room\, Second floor
DESCRIPTION:Speaker: Zalman Balanov (UT at Dallas)\n
\n
Abstract: The van der Pol oscillator (VDPO) consists of an LCR-contour and a \n
negative feedback loop which can be implemented on the basis of a triode. \n
The corresponding second order (autonomous) van der Pol equation is the \n
simplest nonlinear mathematical model widely used in electrical engineering. \n
In practice\, one is usually dealing with networks of VDPOs coupled \n
symmetrically. Studying the impact of symmetries of a system to the actual \n
dynamics (in particular\, symmetric properties and minimal number of periodic \n
regimes) constitutes a problem of great importance and complexity which can \n
be traced back to the classical 16-th Hilbert problem. Periodic \n
solutions to symmetric autonomous systems very often are studied via the \n
so-called equivariant Hopf bifurcation in a parameterized system (i.e. a \n
phenomenon occurring when the parameter crosses some "critical" value causing \n
a change of stability of the "trivial solution"\, which results in \n
appearance of small amplitude non-constant periodic solutions near the \n
trivial one). The commonly used method (M. Golubitsky et al.) is based on \n
the equivariant singularity theory (EST) combined with a Lyapunov-Schmidt \n
reduction or Central Manifold Theorem. However\, this method cannot be \n
applied if the system in question is not smooth enough and/or the phase space \n
does not admit a local linear structure. On the other hand\, if an \n
inductance element in the van der Pol oscillator contains a ferromagnetic \n
core\, the ferromagnetic material can introduce a hysteresis relation between \n
the magnetic induction and magnetic field. In many cases (for example\, in the \n
presence of the ferroresonance phenomenon)\, the hysteresis effect cannot be \n
neglected. As a matter of fact\, systems with hysteresis almost always are \n
non-smooth and the corresponding phase spaces do not admit a local linear \n
structure. Therefore\, the EST based method cannot be applied to them. In my \n
talk\, I will show how an alternative method based on the usage of the new \n
invariant ‚Äì twisted equivariant degree (introduced by Z. Balanov and \n
W. Krawcewicz) -- can be effectively applied to symmetric networks of VDPO \n
with hysteresis. In particular\, a direct link between physics\, topology\, \n
algebra and analysis underlying the VDPOs will be established. This talk \n
is based on a joint work with W. Krawcewicz\, D. Rachinskii and A. \n
Zhezherun.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1497:field_when:0:237
SUMMARY:On some properties of linear spaces and linear operators in the case of \n
quaternionic scalars
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141229T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141229T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1497
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Dr. M. ELENA LUNA-ELIZARRARAS ́ Departamento de Matem ́aticas \n
E.S.F.M. del I.P.N. 07338 M ́exico D.F.\,\n
\n
Abstract:\n
In recent years the study of quaternionic linear spaces has been widely \n
developed\n
by mathematicians and has been widely used by physicists. At the same\n
time it turns out that some basic and fundamental properties of those spaces\n
are not treated properly and this requires to develop the corresponding \n
theory.\n
In this talk we will analyze certain peculiarities of the situation via the \n
notion\n
of quaternionic extension of real and complex linear spaces as well as using \n
the\n
notion of internal quaternionization. We will see\, for example\, how the norms \n
of\n
some operators behave when they are “quaternionically extended”.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1496:field_when:0:238
SUMMARY:Variants and generalizations of Diamond^*
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T112000
URL;VALUE=URI:http://math.biu.ac.il/node/1496
LOCATION:Room 201\, Building 216
DESCRIPTION:Speaker: Efrat Taub (BIU)\n
\n
Abstract:\n
Some combinatorial principles were invented by Jensen\, in his analysis of \n
Godel's constructible universe. One of them is Diamond^*.\n
\n
We will introduce variants and generalizations of Diamond^* and discuss when \n
these principles hold and when they do not hold.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1495:field_when:0:239
SUMMARY:Subfields of quaternion algebras in characteristic 2
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141224T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141224T110000
URL;VALUE=URI:http://math.biu.ac.il/node/1495
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Adam Chapman (Michigan State University)\n
\n
Abstract: We discuss the situation where two quaternion algebras over a field \n
of characteristic 2 share the same genus\, i.e. have the same set of \n
isomorphism classes of quadratic field extension of the center. We provide \n
examples of pairs of nonisomorphic quaternion algebras who satisfy this \n
property\, and show that over global fields and the fields of Laurents series \n
over perfect fields the quaternion algebras are uniquely determined by their \n
maximal subfields. This talk is based on a joint work with Andrew Dolphin and \n
Ahmed Laghribi.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1494:field_when:0:240
SUMMARY:On lattices over valuation rings of arbitrary rank
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141224T110000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141224T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1494
LOCATION:Third floor seminar room
DESCRIPTION:Speaker: Dr. Shaul Zemel (Technische Universität Darmstadt)\n
\n
Abstract: We show how the simple property of 2-Henselianity suffices \n
to reduce the classification of lattices over a general valuation ring \n
in which 2 is invertible (with no restriction on the value group) \n
to classifying quadratic spaces over the residue field. The case where 2 \n
is not invertible is much more difficult. In this case we present \n
the generalized Arf invariant of a unimodular rank 2 lattice\, and show how \n
in case the lattice contains a primitive vector with norm divisible by 2\, \n
a refinement of this invariant and a certain class suffice for \n
classifying these lattices.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1492:field_when:0:241
SUMMARY:Sets of bounded discrepancy for multi-dimensional irrational rotation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141222T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141222T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1492
LOCATION:2nd floor Colloquium Room\, Building 216
DESCRIPTION:Speaker: Dr. Nir Lev\, Bar-Ilan University\n
\n
Abstract:\n
Hecke\, Ostrowski and Kesten characterized the intervals on the circle\n
for which the ergodic sums of their indicator function\, under an\n
irrational rotation\, stay at a bounded distance from their integral\n
with respect to the Lebesgue measure on the circle.\n
In this talk I will discuss this phenomenon in multi-dimensional setting.\n
Based on joint work with Sigrid Grepstad.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1482:field_when:0:242
SUMMARY:The P-hierarchy of ultrafilters
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141214T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141214T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1482
DESCRIPTION:Speaker: Michal Machura (BIU)\n
\n
Abstract:\n
We shall present the P-hierarchy of ultrafilters\, that was posed by Andrzej \n
Starosolski.\n
The P-hierarchy of ultrafilters is one of many ways to classify ultrafilters \n
on natural numbers and it is composed of ℵ1 disjoint classes P(α) where α \n
is ordinal number <ω1. The class P(1) is just a class of principal \n
ultrafilters. The class P(2) is composed of P-points\, which were isolated \n
by Rudin in order to prove non-homogeneity of the remainder of Cech-Stone \n
compactification of natural numbers. Next\, in higher classes of P-hierarchy\, \n
one can find ultrafilters with more and more complicated structures.\n
\n
In this talk\, we will disscuss relations between classes P(α) of P-hierarchy \n
and other special types of ultrafilters\, including: Baumgartner’s \n
I-ultrafilters\, thin ultrafilters\, summable ultrafilters\, and van der Waerden \n
ultrafilters.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1488:field_when:0:243
SUMMARY:Manipulative waiters with probabilistic intuition
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141216T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141216T160000
URL;VALUE=URI:http://math.biu.ac.il/node/1488
DESCRIPTION:Speaker: Dan Hefetz (University of Birmingham)\n
\n
Abstract:\n
The probabilistic intuition is a surprisingly successful heuristic which \n
links the theory of positional games and the theory of random graphs. \n
Positional games are finite\, perfect information two player games with no \n
chance moves and no possibility of a draw. It is known from classical game \n
theory that both players have deterministic optimal strategies for each such \n
game. The probabilistic intuition suggests that a good way of predicting the \n
outcome of such a game under optimal play\, is to study what happens when both \n
players play randomly. In this talk I will present several new results of \n
this type.\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1487:field_when:0:244
SUMMARY:Folding Mathematics into Origami
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141228T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1487
DESCRIPTION:Speaker: Ethan Berkove - Lafayette\n
\n
Abstract:\n
Origami is the traditional Japanese art of paper folding. In the past 30 \n
years investigations into folding properties have not only resulted in many \n
stunning models\, but also a surprising number of applications. In this talk \n
we will provide an introduction to some of the mathematics of folding\, \n
including various theoretical notions of what sorts of folds are possible.\n
\n
\n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1486:field_when:0:245
SUMMARY:Finite determinacy of matrices
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141214T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141214T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1486
DESCRIPTION:Speaker: Dmitry Kerner (BGU)\n
\n
Abstract:\n
Let f be a power series (in several variables) or a C^\infty-smooth function. \n
In many cases just a finite part of Taylor expansion is enough to determine f \n
up to the change of coordinates. Alternatively\, the deformations of f by \n
terms of high enough orders are trivial. This phenomenon is called the finite \n
determinacy.\n
An immediate application is the algebraization: f has a polynomial \n
representative.\n
More generally\, for maps of smooth spaces the finite determinacy (under \n
various group-actions) has been intensively studied for about 50 years (by \n
Mather\, Tougeron\, Arnol'd\, Wall and many others).\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1483:field_when:0:246
SUMMARY:Three faces of equivariant degree
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141215T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141215T150000
URL;VALUE=URI:http://math.biu.ac.il/node/1483
DESCRIPTION:Speaker: Prof. Z. Balanov\, University of Texas at Dallas\n
\n
Abstract:\n
Topological methods based on the usage of degree theory have proved\n
themselves to be an important tool for qualitative studying of solutions to\n
nonlinear differential systems (including such problems as existence\,\n
uniqueness\, multiplicity\, bifurcation\, etc.).\n
\n
During the last twenty years the equivariant degree theory emerged in Non-\n
linear Analysis. In short\, the equivariant degree is a topological tool\n
allowing “counting” orbits of solutions to symmetric equations in the \n
same\n
way as the usual Brouwer degree does\, but according to their symmetry\n
properties. This method is an alternative and/or complement to the\n
equivariant singularity theory developed by M. Golubitsky et al.\, as well as\n
to a variety of methods rooted in Morse theory/Lusternik–Schnirelman \n
theory.\n
\n
In fact\, the equivariant degree has different faces reflecting a diversity of\n
symmetric equations related to applications. In the two talks\, I will discuss\n
three variants of the equivariant degree: (i) non-parameter equivariant\n
degree\, (ii) twisted equivariant degree with one parameter\, and (iii)\n
gradient equivariant degree. Each of the three variants of equivariant degree\n
will be illustrated by appropriate examples of applications: (i) boundary\n
value problems for vector symmetric pendulum equation\, (ii) Hopf bifurcation\n
in symmetric neural networks (simulation of legged locomotion)\, and (iii)\n
bifurcation of relative equilibria in Lennard-Jones three-body problem.\n
\n
The talk is addressed to a general audience\, without any special knowledge\n
of the subject.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1458:field_when:0:247
SUMMARY:High dimensional expanders
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141214T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141214T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1458
DESCRIPTION:Speaker: Tali Kaufman (Bar-Ilan University)\n
\n
Abstract:\n
Expander graphs have been intensively studied in the last four decades. In \n
recent years a high dimensional theory of expanders has emerged. In this \n
talk I will introduce the notion of high dimensional expanders and some of \n
the motivations for studying them. As opposed to (1-dimensional) expanders\, \n
where a random bounded degree graph is an expander\, a probabilistic \n
construction of a bounded degree high dimensional expander is not known. A \n
major open problem\, formulated by Gromov\, is whether *bounded degree* \n
high dimensional expanders could exist for dimension d >= 2. I will \n
discuss a recent construction of explicit bounded degree \n
2-dimensional expanders\, that answer Gromov's question in the affirmative.\n
\n
Joint work with David Kazhdan and Alexander Lubotzky.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1457:field_when:0:248
SUMMARY:Matroids\, log-concavity and measure concentration
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1457
DESCRIPTION:Speaker: Karim Adiprasito (IHES and Hebrew University)\n
\n
Abstract:\n
We provide a simple proof of the Rota--Heron--Welsh conjecture for \n
matroids realizable as c-arrangements in the sense of Goresky--MacPherson: \n
we prove that the coefficients of the characteristic polynomial of the \n
associated matroids form log-concave sequences\, proving the conjecture for a \n
family of matroids out of reach for all previous methods.\n
\n
To this end\, we study the L\'evy--Milman measure concentration phenomenon on \n
natural push-forwards of uniform measures on the Grassmannian to realization \n
spaces of arrangements under a certain extension procedure on matroids.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1455:field_when:0:249
SUMMARY:More on Resolvability of topological spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1455
DESCRIPTION:Speaker: Nir Hakeyni (BIU)\n
\n
Abstract:\n
A topological space is called k-resolvable if it is the union of k many \n
disjoint dense subsets. In this second lecture\, we shall survey some of the \n
results obtained throughout the years and record some open questions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1454:field_when:0:250
SUMMARY:Morphisms of Berkovich analytic curves and the different function
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141210T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141210T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1454
DESCRIPTION:Speaker: Adina Cohen (Hebrew University of Jerusalem)\n
\n
Abstract:\n
In this talk we will study the topological ramification locus of a \n
generically étale morphism f : Y --> X between quasi-smooth Berkovich \n
curves. We define a different function \delta f : Y --> [0\,1] which \n
measures the wildness of the morphism. It turns out to be a piecewise \n
monomial function on the curve\, satisfying a balancing condition at type 2 \n
points analogous to the classical Riemann-Hurwitz formula. We also explain \n
how \delta can be used to explicitly construct the simultaneous skeletons of \n
X and Y.\n
\n
\n
\n
Joint work with Prof. M. Temkin and Dr. D. Trushin.\n
\n
\n
\n
The talk will begin with a quick background on Berkovich curves. All terms \n
will be defined.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1453:field_when:0:251
SUMMARY:Chip ﬁring may be much faster than you think
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T121500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1453
DESCRIPTION:Speaker: Felix Goldberg\n
\n
Abstract:\n
*The chip ring game* Bjorner\, Lovasz and Shor (BLS) introduced the \n
following game in 1991: N chips are placed on the vertices on a n-vertex \n
graph and at every turn\, the solitaire player chooses a vertex i of degree di \n
which has at least di chips on it and "fires" i by shifting a chip from i to \n
each of i's neighbours.\n
*The game duration problem* BLS have proved the remarkable result that \n
whenever this game terminates\, it always does so in the same number of moves\, \n
irrespective of gameplay! (I will explain the background for this). They also \n
gave an elegant upper bound on the number of moves. However\, computer \n
simulation reveals that the game actually ends in far fewer moves than the \n
BLS bound in all examined cases.\n
*The new results* I will show a new approach to obtaining upper bounds on the \n
game duration\, based on a re nement of the classic BLS analysis together with \n
a simple but potent new observation.\n
The new bounds are always at least as good as the BLS bound and in some cases \n
the improvement is dramatic. For example\, for the strongly regular graphs BLS \n
reduces to O(nN) while the new bound reduces to O(n+N). For dense regular \n
graphs BLS reduces to O(N) while the new bound reduces to O(n) (for such it \n
holds that n = O(N)).\n
The proof technique involves a careful analysis of the pseudo-inverse of the \n
graph's discrete Laplacian.\n
*The wider context* Time permitting\, I will also discuss the appearance of \n
chip ring (and its very close relative\, the sandpile model) in diverse \n
mathematical and scientific contexts.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1449:field_when:0:252
SUMMARY:Riesz sequences and arithmetic progressions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141208T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141209T132000
URL;VALUE=URI:http://math.biu.ac.il/node/1449
DESCRIPTION:Speaker: Itay Londner\, Tel-Aviv University\n
\n
Abstract:\n
In the talk\, which is joint work with Alexander Olevskii\, I will present our \n
study of the\n
relationship between the existence of arithmetic progressions with specified \n
lengths and\n
step sizes and lower Riesz bounds of complex exponentials indexed by a set of \n
integers\n
$\Lambda$ on subsets of the circle.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1448:field_when:0:253
SUMMARY:High Spectral Efficiency OFDM Based on Complex Wavelet Packets
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141207T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1448
DESCRIPTION:Speaker: Yosef Ben Ezra - Holon\n
\n
Abstract:\n
(OFDM = Orthogonal frequency-division multiplexing [1]) \n
\n
\n
\n
We propose a novel type of CO-OFDM based on the recently \n
developed dual-tree complex WPT (DT-CWPT). In particular\, polarization mode \n
dispersion (PMD) can be compensated by digital signal processing using a \n
DT-CWPT which is characterized by a single-side band. Numerical simulations \n
show that the 1 Tb/s single-channel CO-OFDM transmission over the distance \n
of 1800 km with the spectral efficiency (SE) of 7.88 bit/s/Hz can be \n
realized.\n
Joint work with D. Brodeski\, B.I. Lembrikov\n
\n
\n
[1] http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing
END:VEVENT
BEGIN:VEVENT
UID:calendar:1446:field_when:0:254
SUMMARY:On the phase transition in random simplicial complexes
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1446
DESCRIPTION:Speaker: Yuval Peled (Hebrew University)\n
\n
Abstract:\n
It is well-known that the G(n\,p) model of random graphs undergoes a dramatic \n
change around p=1/n. It is here that the random graph is\, almost surely\, no \n
longer a forest\, and here it first acquires a giant connected component. \n
Several years ago\, Linial and Meshulam have introduced the X_d(n\,p) model\, a \n
probability space of n-vertex d-dimensional simplicial complexes\, where \n
X_1(n\,p) coincides with G(n\,p). Within this model we prove a natural \n
d-dimensional analog of these graph theoretic phenomena. Specifically\, we \n
determine the exact threshold for the nonvanishing of the real d-th homology \n
of complexes from X_d(n\,p)\, and show that it is strictly greater than the \n
threshold of d-collapsibility. In addition\, we compute the real Betti \n
numbers\, i.e. the dimension of the homology groups\, of X_d(n\,p) for p=c/n. \n
Finally\, we establish the emergence of giant shadow at this threshold. (For \n
d=1 a giant shadow and a giant component are equivalent). Unlike the case for \n
graphs\, for d > 1 the emergence of the giant shadow is a first order phase \n
transition.\n
\n
The talk will contain the necessary toplogical backgorund on simplicial \n
complexes\, and will focus on the main idea of the proof: the local weak limit \n
of random simplicial complexes and its role in the analysis of phase \n
transitions.\n
\n
Joint work with Nati Linial.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1445:field_when:0:255
SUMMARY:Free subgroups of linear groups: geometry\, algebra\, and dynamics
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141203T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141203T113000
URL;VALUE=URI:http://math.biu.ac.il/node/1445
DESCRIPTION:Speaker: Prof. G. A. Soifer (Bar-Ilan University)\n
\n
Abstract:\n
In a celebrated paper\, J. Tits proved the following fundamental dichotomy for \n
a finitely generated linear group:\n
\n
\n
\n
Let G be a finitely generated linear group over an arbitrary field. Then \n
either G is virtually solvable\, or G contains a free non-abelian subgroup.\n
\n
\n
\n
Let G be a non-virtually solvable subgroup of a linear group. We will \n
discuss the following problem(s): is it possible to find a free subgroup of G \n
that fulfills additional (topological\, algebraic\, and dynamical) conditions?
END:VEVENT
BEGIN:VEVENT
UID:calendar:1442:field_when:0:256
SUMMARY:Triple Massey products in Galois cohomology
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1442
DESCRIPTION:Speaker: Eli Matzri\n
\n
Abstract:\n
The Inverse Galois Problem\, asking which groups can be realizable as\n
Galois groups of fields\, is a major problem in Galois theory.\n
For example the fact that there is no general formula for the roots of\n
a polynomial of degree five follows from the fact that\n
the symmetric group S_5\, which is not solvable\, is realizable as a\n
Galois group of a field.\n
Minac and Tan conjectured that if G is the Galois group of a field\,\n
then G has vanishing triple Massey products (to be defined in the lecture).\n
In the talk I will give some general background on this new property\n
and its relation to the inverse Galois problem via a work of Dwyer\, and try \n
to give a\n
flavor of my proof of the Minac-Tan conjecture.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1444:field_when:0:257
SUMMARY:Resolvability of topological spaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1444
DESCRIPTION:Speaker: Nir Hakeyni (BIU)\n
\n
Abstract:\n
A topological space is called /resolvable/ if it is the union of two disjoint \n
dense subsets. Since the concept was first defined and explored by Edwin \n
Hewitt in 1943\, much effort has been invested in obtaining general results \n
concerning the resolvability or irresolvability of certain types of spaces\, \n
and in generating examples and counterexamples.\n
In the present lecture we will take a leisurely tour through the subject. We \n
will discuss generalizations of the original concept\, display some of the \n
results obtained throughout the years and mention questions which are still \n
open.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1443:field_when:0:258
SUMMARY:Certain problems in Fourier Analysis
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141201T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141201T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1443
DESCRIPTION:Speaker: Prof. R. Trigub\, Donetsk National University\, Ukraine\n
\n
Abstract:\n
The following problems (or a part of them) will be discussed.\n
1. Generalization of the Abel-Poisson summation method. \n
2. Generalization of the Riemann-Lebesgue lemma.\n
3. Strengthening of the Hardy-McGehee-Pigno-Smith inequality.\n
4. Generalization of the Euler-Maclaurin formula.\n
5. Absolute convergence of grouped Fourier series.\n
6. Comparison of linear differential operators with constant coefficients.\n
7. Positive definite functions and splines.\n
8. Strong converse theorems in approximation theory. Bernstein-Stechkin \n
polynomials.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1439:field_when:0:259
SUMMARY:Triangles in H-free graphs
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T153000
URL;VALUE=URI:http://math.biu.ac.il/node/1439
DESCRIPTION:Speaker: Clara Shikhelman (Tel-Aviv University)\n
\n
Abstract:\n
For two graphs T and H and an integer n\, let ex(n\, T\, H) denote the maximum \n
possible number of copies of T in an H-free graph on n vertices. The study of \n
this function when T = K_2 (a single edge) is one of the main subjects of \n
extremal graph theory. We investigate the general function\, focusing on the \n
case T = K_3\, which reveals several interesting phenomena.\n
\n
In this talk we will present proofs of the following main results: (i) For \n
any fixed s > 1 and t > (s-1) one has ex(n\,K_3\,K_{s\,t})=\Theta(n^{3-3/s})\, \n
and (ii) ex(n\,K_3\,C_5) < (1+o(1)) (\sqrt 3)/2 n^{3/2}.\n
The last statement improves (slightly) a result of Bollobas and Gyori.\n
\n
Joint work with Noga Alon.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1438:field_when:0:260
SUMMARY:Entire functions of exponential type represented by pseudo-random and random \n
Taylor series
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141124T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141124T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1438
DESCRIPTION:Speaker: Prof. M. Sodin\, Tel-Aviv University\n
\n
Abstract:\n
We study the influence the angular distribution of zeroes of the Taylor\n
series with pseudo-random and random coefficients\, and show that the\n
distribution of zeroes is governed by certain autocorrelations of the\n
coefficients. Using this guiding principle\, we consider several examples\n
of random and pseudo-random sequences $\xi$ and\, in particular\, answer\n
some questions posed by Chen and Littlewood in 1967.\n
\n
As a by-product we show that if $\xi$ is a stationary random\n
integer-valued sequence\, then either it is periodic\, or its spectral\n
measure has no gaps in its support. The same conclusion is true if $\xi$\n
is a complex-valued stationary ergodic sequence that takes values from a\n
uniformly discrete set (joint work with Alexander Borichev and Alon Nishry).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1437:field_when:0:261
SUMMARY:Entire functions of exponential type represented by pseudo-random and random \n
Taylor series
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141117T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141117T231000
URL;VALUE=URI:http://math.biu.ac.il/node/1437
DESCRIPTION:Speaker: Prof. M. Sodin\, Tel-Aviv University\n
\n
Abstract:\n
We study the influence the angular distribution of zeroes of the Taylor\n
series with pseudo-random and random coefficients\, and show that the\n
distribution of zeroes is governed by certain autocorrelations of the\n
coefficients. Using this guiding principle\, we consider several examples\n
of random and pseudo-random sequences $\xi$ and\, in particular\, answer\n
some questions posed by Chen and Littlewood in 1967.\n
\n
As a by-product we show that if $\xi$ is a stationary random\n
integer-valued sequence\, then either it is periodic\, or its spectral\n
measure has no gaps in its support. The same conclusion is true if $\xi$ \n
is a complex-valued stationary ergodic sequence that takes values from a \n
uniformly discrete set (joint work with Alexander Borichev and Alon Nishry).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1436:field_when:0:262
SUMMARY:Ruled common nodal surfaces
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141117T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141117T230000
URL;VALUE=URI:http://math.biu.ac.il/node/1436
DESCRIPTION:Speaker: Prof. M. Agranovsky\, Bar-Ilan University\n
\n
Abstract:\n
Nodal sets are zero loci of Laplace eigenfunctions (e.f.). Study of nodal \n
sets is important\n
for understanding wave processes. The geometry of a single nodal set may be \n
very complicated\n
and hardly can be well understood. More realistic might be describing \n
geometry of sets which\n
are nodal for a large family of e.f. (the condition of simultaneous \n
vanishing\, resonanse\, of\n
a large packet of e.f.\, on a large set\, is overdetermined and hence may be \n
expected to occur\n
only for exclusive sets).\n
\n
Indeed\, it was proved that common nodal curves for large\, in different \n
senses\, families\n
of e.f. in $\mathbb R^2$ are straight lines (non-periodic case: Quinto and \n
the speaker\, ’96\; periodic\n
case: Bourgain and Rudnick\, ’11). It was conjectured that in a Euclidean \n
space of\n
arbitrary dimension\, common nodal hypersurfaces for large families of e.f. \n
are cones\, more precisely\,\n
are translates of zero sets of harmonic homogeneous polynomials.\n
\n
The talk will be devoted to a recent result confirming the conjecture for \n
ruled hypersurfaces\n
in $\mathbb R^3$. Relation to the injectivity problem for the spherical Radon \n
transform will be explained.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1435:field_when:0:263
SUMMARY:Beurling's method in the theory of quasianalytic functions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141103T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141117T230000
URL;VALUE=URI:http://math.biu.ac.il/node/1435
DESCRIPTION:Speaker: Avner Kiro\, Tel-Aviv University\n
\n
Abstract:\n
The talk is will be devoted to two questions in the theory of \n
quasianalytic \n
Carleman classes. The first one is how to describe the image of a \n
quasianalytic \n
Carleman class under Borel's map $f\to\{f^{(n)}(0)/n!\}_{n\geq 0}$ ? \n
The second one is how to sum the formal Taylor series of functions in \n
quasianalytic Carleman classes? In the talk\, I will present a method of \n
Beurling that gives a solution to both of the problems for some quasianalytic \n
Carleman classes. If time permits\, I will also discuss the image problem in \n
some non-quasianalytic classes.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1434:field_when:0:264
SUMMARY:A Theory of Stationary Trees and the Balanced Baumgartner-Hajnal-Todorcevic \n
Theorem for Trees
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T120000
URL;VALUE=URI:http://math.biu.ac.il/node/1434
DESCRIPTION:Speaker: Ari Brodsky (BIU)\n
\n
Abstract:\n
We shall discuss generalizations of Ramsey's theorem to the context of trees \n
of high chromatic number. A detailed abstract is available here [1].\n
\n
\n
\n
Bibliograpy [2]\n
\n
\n
\n
\n
[1] http://settheory.mathtalks.org/?p=5404\n
[2] http://individual.utoronto.ca/aribrodsky/Brodsky_Ari_M_201406_PhD_thesis.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:1433:field_when:0:265
SUMMARY:Interdependencies in the financial global village
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141130T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1433
DESCRIPTION:Speaker: Dror Kenett - Boston U\n
\n
Abstract:\n
This talk will present a new framework for quantification of the coupling and \n
interdependences between different financial markets. The employment of ideas \n
and techniques from complexity science and the proposed theory of coupled and \n
interdependent networks to understand and quantify the role of connections \n
and dependencies within a system and between different ones opens the \n
possibility to manage the complexity\, optimize the systems and reduce their \n
vulnerability to failures. More specifically\, we investigate the stock-stock \n
correlations in individual markets as local market dynamics\, and the \n
correlation of correlations\, meta-correlations\, which represents global \n
market dynamics. Furthermore\, we make use of the recently introduced \n
dependency network methodology\, which enables a quantification of the \n
influence relationships between the different markets. The methodologies \n
presented provide the means to track the flow of information between \n
different markets\, and can be used to identify changes in correlations in \n
strongly coupled markets. Finally\, we will discuss different applications of \n
network science in finance and economics\, which demonstrate who one can use \n
empirical financial data to construct a network that represents the financial \n
system\, and then use it to study different aspects such as structure\, \n
dynamics and stability.\n
\n
The world has become a global village\, and this village is becoming smaller \n
and smaller\, with the continuous introduction of ways to interact and connect \n
to other people. Thus\, the methodology outlined in this talk will provide new \n
tools and means to quantify\, characterize and manage the complexity of the \n
world’s economy. The methodologies presented here can be used as the basis \n
for quantitative early warning tool\, a “financial seismograph”\, which \n
will provide policy makers the necessary precursors for significant local and \n
global economic events.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1432:field_when:0:266
SUMMARY:Group theoretic methods in non-free ergodic theory
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1432
DESCRIPTION:Speaker: Yair Glasner (BGU)\n
\n
Abstract:\n
Ergodic theory studies actions of a group G by measure preserving \n
transformations on a probability space. Usually the focus is on "essentially \n
free" actions\, namely actions for which almost all stabilizers are tirival. \n
Classically the methods are analitic and combinatorial. \n
\n
Recently it becomes more and more clear that in the study of non essentially \n
free actions - sophisticated group theoretic tools also come into the \n
picture. I will try to demonstrate this by an array of recent results due to \n
Bader-Lacreux-Duchnese\, Tucker-Drob\, as well as some joint papers with Abert \n
and Virag and myself.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1428:field_when:0:267
SUMMARY:How hard is it to recognize a sphere?
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141116T120000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141116T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1428
DESCRIPTION:Speaker: Joel Hass (UC Davis)\n
\n
Abstract: I will talk about recent work showing that the problem of \n
recognizing the 3-sphere lies in the class NP intersect coNP\, assuming the \n
Generalized Riemann Hypothesis. This is joint work with Greg Kuperberg.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1429:field_when:0:268
SUMMARY:Massey products in Galois theory
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141126T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141126T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1429
DESCRIPTION:Speaker: Prof. Ido Efrat (Ben Gurion University)\n
\n
Abstract:\n
We will report on several recent works on Massey products in Galois \n
cohomology\,\n
and explain how they reveal new information on the structure of absolute \n
Galois groups of fields.\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1417:field_when:0:269
SUMMARY:Well-colorings and the Hanf number for amalgamation
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141109T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141109T100000
URL;VALUE=URI:http://math.biu.ac.il/node/1417
DESCRIPTION:Speaker: Chris Lambie-Hanson (HUJI)\n
\n
Abstract:\n
The amalgamation property is a topic of fundamental interest in model theory \n
and is still imperfectly understood. In the 1980s\, Grossberg asked a \n
question\, which remains open to this day\, about the existence of a Hanf \n
number for amalgamation in abstract elementary classes. We introduce a new \n
class of structures\, called well-colorings\, and use them to give a partial \n
answer to Grossberg’s question\, significantly improving upon previous work \n
of Baldwin\, Kolesnikov\, and Shelah. We shall start the talk by briefly \n
discussing the relevant model-theoretic definitions (no prior model-theoretic \n
knowledge will be assumed) and will then give proofs of the main results\, \n
which are entirely set-theoretic and combinatorial in nature and of interest \n
in their own right. This is joint work with Alexei Kolesnikov.\n
\n
\n
\n
Bibliography [1]\n
\n
\n
[1] http://arxiv.org/abs/1409.2508
END:VEVENT
BEGIN:VEVENT
UID:calendar:1427:field_when:0:270
SUMMARY:Avoiding rational distances
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141116T101500
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141116T101500
URL;VALUE=URI:http://math.biu.ac.il/node/1427
DESCRIPTION:Speaker: Ashutosh Kumar (HUJI)\n
\n
Abstract:\n
Komjath has asked the following question: Let X be a subset of Euclidean \n
space. Must there exist a subset Y of X such that X and Y have same outer \n
measure and the distance between any two points in Y is irrational? \n
\n
We'll show that this is true in dimension one. Our proof relies on some \n
work of Gitik and Shelah on forcings with sigma ideals. Bibliography [1]\n
\n
[1] http://arxiv.org/abs/1207.5029
END:VEVENT
BEGIN:VEVENT
UID:calendar:1426:field_when:0:271
SUMMARY:Diophantine and cohomological dimensions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141119T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141119T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1426
DESCRIPTION:Speaker: Dr. Eli Matzri (Ben Gurion University)\n
\n
Abstract:\n
We give explicit linear bounds on the p-cohomological dimension\n
of a field in terms of its Diophantine dimension. In particular\,\n
we show that for a field of Diophantine dimension at most 4\, the\n
3-cohomological dimension is less than or equal to the Diophantine dimension.\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1425:field_when:0:272
SUMMARY:Counting commensurability classes of hyperbolic manifolds
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141112T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141112T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1425
DESCRIPTION:Speaker: Arie Levit (Weizmann Institute of Science)\n
\n
Abstract: Subgroup growth usually means the asymptotic behavior of the number \n
of subgroups of index n of a given f.g. group as a function of n. We \n
generalize this to discrete (torsion-free) subgroups of the Lie group \n
G=SO+(n\,1) for which the quotient admits finite volume\, as a function of the \n
co-volume. Conjugacy classes of such discrete subgroups correspond \n
geometrically to n-dimensional hyperbolic manifolds of finite volume.\n
\n
\n
By a classical result of Wang\, for n >=4 there are only finitely many such \n
conjugacy classes up to any given finite volume V. More recently\, Burger\, \n
Gelander\, Lubotzky and Mozes showed that this number grows like V^V. In \n
this talk we focus on counting commensurability classes. Two subgroups \n
are commensurable if they admit a common finite index subgroup (in our \n
context\, up to taking conjugates). We show that surprisingly\, for n >= 4 this \n
number grows like V^V as well. Since the number of \n
arithmetic commensurability classes grows ~polynomially (Belolipetsky)\, \n
our result implies that non-arithmetic subgroups account for \n
“most" commensurability classes. Our proof uses a mixture of \n
arithmetic\, hyperbolic geometry and some combinatorics. In particular\, recall \n
that a quadratic form of signature (n\,1) over a totally real number field\, \n
whose conjugates are positive definite\, defines an arithmetic discrete \n
subgroup of finite covolume in G. As in the classical construction of \n
Gromov--Piatetski-Shapiro\, several non-similar quadratic forms can be \n
combined to construct amalgamated non-arithmetic subgroups.\n
This is a joint work with Tsachik Gelander.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1422:field_when:0:273
SUMMARY:A Robust Shadow Matching Algorithm for GNSS Positioning
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141123T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1422
DESCRIPTION:Speaker: Boaz Ben Moshe - Ariel\n
\n
Abstract:\n
Commercial GNSS devices tend to perform poorly in urban \n
canyon environments. The dense and tall buildings block the signals from \n
many of the satellites. In this talk\, we present a particle filter \n
algorithm for Shadow Matching framework to face this problem. Given a 3D \n
city map and given the\n
satellites' signal properties\, the algorithm calculates in \n
real-time invalid regions inside the Region Of Interest (ROI). This approach \n
reduces the ROI to a fraction of its original size. We present a general \n
framework for Shadow Matching positioning algorithm based on a modified \n
particle filter. Using simulation experiments we have shown that the \n
suggested method can improve the accuracy of existing GNSS devices in urban \n
regions. Moreover\, the proposed algorithm can be efficiently extended to \n
3D positioning in high sampling rate\, inherently applicable for UAVs \n
and Drones.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1420:field_when:0:274
SUMMARY:The local theory of tournaments
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141116T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141116T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1420
DESCRIPTION:Speaker: Avraham Morgenstern (Hebrew University)\n
\n
Abstract:\n
\n
\n
The Erd\H{o}s-Hajnal conjecture states that for every graph H there exists an \n
injection of H into G for every large graph G whose largest homogeneous \n
subset (clique or anti-clique) is sub-polynomial in |G|. We formulate a local \n
version of this conjecture\, and prove it for all 3-vertex graphs H. We prove \n
the tournament analog for all 4-vertex tournaments H.\n
\n
\n
We initiate the study of the 4-local profiles of tournaments\, and derive some \n
bounds on these sets. In particular\, given the number of cycles of length 3\, \n
which tournaments minimize the number of cycles of length 4? Given the number \n
of transitive triangles\, which tournaments minimize the number of transitive \n
quadruples? We state a conjecture\, and derive an almost matching bound. We \n
show that these two questions are equivalent\, and describe some related \n
questions. For example: Can the cyclic triangles be uniformly distributed \n
along the edges of a large tournament? (answer: No\, except for trivial \n
cases). Joint Work with Nati Linial.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1413:field_when:0:275
SUMMARY:Fractional matchings and covers in families of (weighted) d-intervals
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141102T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141102T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1413
DESCRIPTION:Speaker: Shira Zerbib (Technion)\n
\n
Abstract:\n
A $d$-interval hypergraph consists of edges that are each the union of $d$ \n
closed intervals on the real line. Kaiser showed that the ratio between the \n
covering number and the matching number in such hypergraphs is bounded by \n
$d^2-d+1$. I will present some new results regarding the weighted and \n
fractional versions of this theorem\, and examples for their sharpness. To \n
this end I will describe a weighted version of Tur\'{a}n's theorem. I will \n
also discuss an extension of the KKM theorem (due to Shapley) and use it to \n
give a straightforward proof to Kaiser's theorem.\n
\n
\n
Joint work with R. Aharoni and T. Kaiser.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1419:field_when:0:276
SUMMARY:On the influences of low degree bounded functions
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141109T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141109T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1419
DESCRIPTION:Speaker: Noam Lifshitz (Bar-Ilan University)\n
\n
Abstract:\n
The influence of the $k$-th coordinate on a Boolean function $f$ measures how \n
likely is $f(x)$ to change when the $k$-th coordinate of $x$ is flipped \n
while the other coordinates remain unchanged. Influences were studied \n
extensively in the last 25 years\, and they have applications \n
to theoretical computer science\, mathematical physics\, and various other \n
fields.\n
\n
In this talk we consider bounded functions on the discrete cube\, i.e.\, \n
$f:{-1\,1}^n -> [-1\,1]$. In this case\, one of the natural definitions of \n
influence is the $L_1$ influence\, defined as $I_k(f)=E[ |f(x)-f(x+e_k)| ]$. \n
We study the following question\, raised by Aaronson and Ambainis in the \n
context of quantum computation. Assume that $f$ has degree $d$ as a \n
multilinear polynomial. Is it true that the sum of $L_1$ influences of $f$ \n
can be bounded as a function of $d$ (independent of $n$)?\n
\n
In a recent paper\, Backurs and Bavarian showed an upper bound of $O(d^3)$ for \n
general functions and $O(d^2)$ for homogeneous functions. We improve the \n
upper bounds to $d^2$ for general functions and $O(d \log d)$ for \n
homogeneous functions. Furthermore\, we present an upper bound of $d / \n
2\pi$ for monotone functions and show that it is tight. Our proofs use tools \n
from approximation theory\, such as Bernstein-Markov type inequalities.\n
\n
Joint work with Yuval Filmus (IAS)\, Hamed Hatami (McGill)\, and Nathan Keller.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1412:field_when:0:277
SUMMARY:Peeking into the black box: reverse engineering the dynamics of complex \n
systems
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141109T130000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141109T130000
URL;VALUE=URI:http://math.biu.ac.il/node/1412
DESCRIPTION:Speaker: Baruch Barzel\, BIU\n
\n
Abstract:\n
The recent years have seen spectacular advances in our understanding of the \n
structure of complex networks\, providing detailed maps of social \n
and technological systems\, cellular networks and food webs. The ultimate \n
goal of these efforts is to be able to translate these topological findings \n
into dynamical predictions on the system's observable behavior. However\, \n
our progress in this direction is hindered by a crucial lacuna: *the \n
absence of microscopic models that describe the dynamics of many of the \n
relevant complex systems*. The challenge is that these systems are\, in \n
effect\, a black box. We can observe \n
their macroscopic behavior\, e.g.\, track the spread of an epidemic\, \n
but we have no direct access to the microscopic exchanges taking place \n
between the nodes\, i.e. the dynamical model that most accurately describes \n
the processes of infection and recovery. Metaphorically\, the task of \n
unveiling these microscopic dynamics\, is equivalent with an attempt to \n
recover the structure of a car's engine directly from observations of its \n
macro-scale behavior\, having no direct access to what is under the hood. \n
Hence we developed a reverse engineering method to infer the microscopic \n
dynamics of a complex system directly from observations of its response to \n
external perturbations. The formalism allows us to construct the most \n
general class of continuum models that are consistent with the observed \n
behavior.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1407:field_when:0:278
SUMMARY:Preservation of the higher chain condition under products
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141102T100000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141102T100000
URL;VALUE=URI:http://math.biu.ac.il/node/1407
DESCRIPTION:Speaker: Assaf Rinot\n
\n
Abstract:\n
We shall survey the history of the study of the productivity of the \n
k-chain-condition in partial orders\, topological spaces\, and Boolean \n
algebras. We shall address a conjecture that tries to characterize such a \n
productivity in Ramsey-type language. For this\, a new oscillation function \n
for successor cardinals\, and a new characteristic function for walks on \n
ordinals will be proposed and investigated.\n
\n
\n
Bibliography [1]\n
\n
\n
[1] http://www.assafrinot.com/paper/18
END:VEVENT
BEGIN:VEVENT
UID:calendar:1411:field_when:0:279
SUMMARY:Representation zeta functions of norm one subgroups of a local division \n
algebra
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141105T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141105T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1411
DESCRIPTION:Speaker: Shai Shechter (Ben Gurion University)\n
\n
Abstract:\n
See attached file.\n
\n
http://math.biu.ac.il/files/math/seminars/abstract-2.pdf
END:VEVENT
BEGIN:VEVENT
UID:calendar:1410:field_when:0:280
SUMMARY:Banach Algebraic Geometry
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141029T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20141029T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1410
DESCRIPTION:Speaker: Dr. Oren Ben-Bassat (University of Oxford and University of Haifa)\n
\n
Abstract:\n
I will present a 'categorical' way of doing analytic geometry in which \n
analytic geometry is seen as a precise analogue of algebraic geometry. Our \n
approach works for both complex analytic geometry and p-adic analytic \n
geometry in a uniform way. I will focus on the idea of an 'open set' as used \n
in these various areas of math and how it is characterised categorically. In \n
order to do this\, we need to study algebras and their modules in the category \n
of Banach spaces. The categorical characterization that we need uses \n
homological algebra in these 'quasi-abelian' categories which is work of \n
Schneiders and Prosmans. In fact\, we work with the larger category of \n
Ind-Banach spaces for reasons I will explain. This gives us a way to \n
establish foundations of analytic geometry and to compare with the standard \n
notions such as the theory of affinoid algebras\, Grosse-Klonne's theory of \n
dagger algebras (over-convergent functions) and others. If time remains I \n
will explain how this extends to a formulation of derived analytic geometry \n
following the relative algebraic geometry approach of Toen\, Vaquie and \n
Vezzosi.\n
\n
\n
\n
This is joint work with Federico Bambozzi (Regensburg) and Kobi Kremnizer \n
(Oxford).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1355:field_when:0:281
SUMMARY:About Sign-Constancy of Green's Functions for Impulsive Second Order Delay \n
Equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140608T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140608T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1355
DESCRIPTION:Speaker: Guy Lendesman - BIU\n
\n
Abstract:\n
We consider a second order delay differential equation with impulses. In this \n
paper we find necessary and sufficient conditions of positivity of Green's \n
functions for this impulsive equation coupled with one or two-point boundary \n
conditions in the form of theorems about differential inequalities. By \n
choosing the test function in these theorems\, we obtain simple sufficient \n
conditions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1354:field_when:0:282
SUMMARY:Hypergroups and their convolution algebras of multilinear forms
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140602T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140602T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1354
DESCRIPTION:Speaker: Prof. Bert Schreiber\, Wayne State University\, Detroit\, USA\n
\n
Abstract:\n
We will begin by introducing the notion of hypergroup\, give some examples\, \n
and describe the convolution of measures on a hypergroup. After a review of \n
some basic operator space theory\, we shall describe how to extend the \n
notion \n
of convolution to the space of completely bounded multilinear forms on a \n
cartesian \n
product of spaces of continuous functions on hypergroups\, thus making that \n
space \n
into a Banach algebra. When the hypergroups are commutative\, we introduce and \n
study \n
a notion of Fourier transform in this setting.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1353:field_when:0:283
SUMMARY:Essential spectrum of Operators of Quantum Mechanics and Limit Operators
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140526T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140526T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1353
DESCRIPTION:Speaker: Prof. V. Rabinovich\, National Polytechnic Institute of Mexico\n
\n
Abstract:\n
The talk is devoted to applications of the limit operators to the study of\n
essential spectra and exponential decay of eigenfunctions of the discrete\n
spectra for Schr\"{o}dinger and Dirac operators for wide classes of\n
potentials. Outline of the talk:\n
\n
1) Fredholm property and location of the essential spectrum of systems of\n
partial differential operators with variable bounded coefficients\;\n
\n
2) Exponential estimates of solutions of systems of partial differential\n
operators with variable bounded coefficients\;\n
\n
3) Location of the essential spectrum of Schr\"{o}dinger and Dirac operators\n
and exponential estimates of eigenfunctions of the discrete spectrum.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1347:field_when:0:284
SUMMARY:Social Choice: A Dynamical Consensus Model
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140518T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140518T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1347
DESCRIPTION:Speaker: Boris Brodsky - State University of Moscow\n
\n
Abstract:\n
The main conclusion of more than 50 years of evolution of the theory of \n
social choice (Mueller\, 2000) is as follows: in the world constructed \n
according to Arrow’s model of social choice only diﬀerent forms of \n
collective oppression can exist. Weale (Theory of Choice\, 1992) gives the \n
following vision of an alternative model of social choice: "An alternative \n
model of collective choice would be most likely to present it not as a \n
process of preference aggregation\, in which there is a mapping from a set of \n
individual orderings to a social ordering\, but as a process of dialog in \n
which reasons are exchanged between participants in a process that is \n
perceived to be a joint search for a consensus".\n
\n
In this report I aim at construction of this alternative model of social \n
choice based on the value-powered exchange of economic or symbolic goods. I \n
demonstrate below that under some natural hypotheses about individual demand \n
and supply functions of goods\, the social consensus is possible\, i.e. there \n
exist stable stationary points in multivariate systems of social exchange of \n
economic or symbolic goods. These stable stationary points are interpreted as \n
the social consensus points in dialogic (or poly-logic) processes of social \n
choice.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1349:field_when:0:285
SUMMARY:Optimal estimates for derivatives of analytic functions and solutions to \n
Laplace\, Lam\'e and Stokes equations
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140519T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140519T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1349
DESCRIPTION:Speaker: Prof. Gershon Kresin\, Ariel University\n
\n
Abstract:\n
Two types of optimal estimates for derivatives of analytic functions\n
with bounded real part are considered. The first of them is a pointwise\n
inequality for derivatives of analytic functions in the complement\n
of a convex closed domain in ${\mathbb C}$. The second type of inequalities\n
is a limit relation for derivatives of analytic functions in an arbitrary \n
proper\n
subdomain of ${\mathbb C}$. Optimal estimates for derivatives of a vector\n
field with bounded harmonic components as well as optimal estimates for the\n
divergence of an elastic displacement field and pressure in a fluid in\n
subdomains of ${\mathbb R}^n$ are discussed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1344:field_when:0:286
SUMMARY:Stability theorems for exponential bases in $L^2$
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140512T140000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140512T140000
URL;VALUE=URI:http://math.biu.ac.il/node/1344
DESCRIPTION:Speaker: Prof. L. De Carli\, Florida International University\n
\n
Abstract:\n
Let $D$ be a domain of $\R^d$\; we say that $L^2(D)$ has an exponential basis \n
if there exists \n
\n
sequence of functions ${\mathcal B}=\{ e^{2\pi i \langle s_m x\rangle}\}_{ \n
m \in Z^d}$\, \n
with $s_m\in\R^d$\, with the following property: every function in $L^2(D)$ \n
can be written in \n
a unique way as $\sum_{m\in\Z^d} c_m e^{ 2\pi i \langle s_m\, \n
x\rangle} $\, with $c_m \in \C$. \n
For example\, $\{ e^{2\pi i mx}\} _{m \in Z}$ is an exponential basis of \n
$L^2(0\, 1 )$. \n
Exponential bases are very useful in the application\, especially when they \n
are orthogonal\; however\, \n
the existence or non-existence of exponential bases is proved only on \n
very special domains of $\R^d$. \n
In particular\, it is not known whether the unit ball in $\R^2$ has an \n
exponential basis or not.\n
\n
An important property of exponential bases is their stability. That is\, if \n
$\{ e^{2\pi i \langle s_m\, \n
x\rangle}\}_{ m \in Z^d}$ is an exponential basis of $L^2(D)$ and \n
$\Delta=\{\delta_m\}_{ m \in Z^d} $ is \n
a sequence of sufficiently small real number\, then also $\{ e^{2\pi i \n
\langle s_m+\delta_m\, \n
x\rangle}\}_{ m \in Z^d}$ is an exponential basis of $L^2(D)$. In this \n
talk I will discuss the existence \n
and stability of exponential bases on special 2-dimensional domains called \n
trapezoids.\n
I will also generalize a celebrate theorem by M. Kadec and obtain \n
stability bounds for exponential bases on domains of $\R^d$.\n
The result that I will present in my talk are part of joint projects with my \n
students A. Kumar and S. Pathak.\n
\n
END_OF_ABSTRACT
END:VEVENT
BEGIN:VEVENT
UID:calendar:1342:field_when:0:287
SUMMARY:Representation zeta functions of finitely generated nilpotent groups and \n
generating functions for hyperoctahedral groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140514T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140514T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1342
DESCRIPTION:Speaker: Prof. Christopher Voll (Bielefeld University)\n
\n
Abstract:\n
The representation zeta function of a finitely generated nilpotent group is \n
the Dirichlet generating series enumerating the group's irreducible \n
finite-dimensional complex characters up to twists by one-dimensional \n
characters. A simple example is the Heisenberg group over the integers: here \n
the relevant arithmetic function is just Euler's totient function. In \n
general\, these zeta functions have natural Euler product decompositions\, \n
indexed by the places of a number field. The Euler factors are rational \n
functions with interesting arithmetic properties\, such as palindromic \n
symmetries.\n
In my talk -- which reports on joint work with Alexander Stasinski -- I will \n
(A) explain some general facts about representation zeta functions of \n
finitely generated nilpotent groups and (B) discuss in detail some specific \n
classes of examples\, including groups generalizing the free class-2-nilpotent \n
groups. One reason for interest in these classes of groups is the fact that \n
their representation growth exhibits intriguing connections with some \n
statistics on the hyperoctahedral groups (Weyl groups of type B).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1341:field_when:0:288
SUMMARY:Filtrations of absolute Galois groups
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140430T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140430T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1341
DESCRIPTION:Speaker: Prof. Ido Efrat (Ben-Gurion University)\n
\n
Abstract:\n
A profinite group is equipped with various standard filtrations by closed \n
normal subgroup\,\n
such as the lower central series\, the lower p-central series\, and the \n
p-Zassenhaus filtration.\n
In the case of an absolute Galois group of a field\, these filtrations are \n
related to the arithmetic \n
structure of the field\, as well as with its Galois cohomology. We will \n
describe some recent \n
results on these connections\, in particular with the Massy product in Galois \n
cohomology. \n
\n
END:VEVENT
BEGIN:VEVENT
UID:calendar:1340:field_when:0:289
SUMMARY:Characteristic Polynomials of Supertropical Matrices
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140507T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140507T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1340
DESCRIPTION:Speaker: Adi Niv (Bar-Ilan University)\n
\n
Abstract: The Max-Plus (tropical) algebra\, is the set of real numbers R\, \n
together with -\infty\, equipped with the operations maximum and the usual \n
plus. We start by presenting some basic notation in this setting\, and \n
show how the lack of additive inverse causes failure of some classic \n
algebraic properties. Then\, we present the extended (supertropical) algebra\, \n
introduced and studied by Izhakian and Rowen\, which adds a layer of singular \n
elements to R. We show how this extension recovers these failed properties. \n
In the last part we introduce definitions and theorems in supertropical \n
linear algebra\, and state the connection between the eigenvalues of a matrix \n
to those of its powers\, tropical-inverse and conjugates. If time allows\, we \n
will give some details of the proof. *The results on characteristic \n
polynomials are a part of the speaker's PhD thesis.
END:VEVENT
BEGIN:VEVENT
UID:calendar:1339:field_when:0:290
SUMMARY:From Nilpotent groups to Nilpotent Hopf algebras and beyond
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140521T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140521T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1339
DESCRIPTION:Speaker: Prof. Miriam Cohen (Ben-Gurion University)\n
\n
Abstract:\n
Generalizing the notion of nilpotency of groups to nilpotency of semisimple \n
Hopf\n
\n
algebras H we give several criteria for H to be nilpotent in terms\n
\n
of various sequences of "commutators" and canonical matrices associated to H. \n
We also initiate the study of probabilistical methods for Hopf algebras and \n
prove that quasi-triangular H are\n
\n
“probabilistically nilpotent” ( If G is a finite group then its group \n
algebra kG is an example of such H).
END:VEVENT
BEGIN:VEVENT
UID:calendar:1335:field_when:0:291
SUMMARY:Feedback between node and network dynamics can produce real world network \n
properties\, and network structure is developed through localized bursts in \n
time and space
DTSTAMP;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20170427T174749
DTSTART;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140504T103000
DTEND;TZID=Asia/Tel_Aviv;VALUE=DATE-TIME:20140504T103000
URL;VALUE=URI:http://math.biu.ac.il/node/1335
DESCRIPTION:Speaker: Hila Brot\, BIU\n
\n
Abstract:\n
Real world networks are characterized by common features\, including among \n
others a scale free degree distribution\, a high clustering coefficient and a \n
short typical distance between nodes. These properties are usually explained \n
by the dynamics of edge and node addition and deletion.\n
\n
We here propose to combine the dynamics of the nodes content and of the edges \n
addition and deletion\, using a threshold automata framework. Within this \n
framework\, we show that the typical properties of real world networks can be \n
reproduced with a Hebbian approach\, in which nodes with similar internal \n
dynamics have a high probability of being connected. The proper network \n
properties emerge only if an imbalance exists between excitatory and \n
inhibitory connections\, as is indeed observed in real networks.\n
\n
We further check the plausibility of the suggested mechanism by observing an \n
evolving social network and measuring the probability of edge addition as a \n
function of similarity between contents of the corresponding nodes. We indeed \n
find that similarity between nodes increases the emergence probability of a \n
new link between them.
END:VEVENT
END:VCALENDAR