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X-WR-CALNAME;VALUE=TEXT:סמינרים | המחלקה למתמטיקה
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BEGIN:VEVENT
UID:calendar:3190:field_when:0:0
SUMMARY:Stationary reflection and Prikry forcing, part 2
DTSTART:2021-03-10T12:00:00
DTEND:2021-03-10T14:00:00
DSCRIPTION:Speaker: Yair Hayut (HUJI)\n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3185:field_when:0:1
SUMMARY:Generating algebras over commutative rings
DTSTART:2021-03-10T08:30:00
DTEND:2021-03-10T09:30:00
DSCRIPTION:Speaker: Dr. Uriya First (Haifa University)\n
Abstract:
Let R be a noetherian (commutative) ring of Krull dimension d. A classical theorem of Forster states that a rank-n locally free R-module can be generated by n+d elements. Swan and Chase observed that this upper bound cannot be improved in general. I will discuss a joint work with Zinovy Reichstein and Ben Williams where similar upper and lower bounds are obtained for R-algebras, provided that R is of finite type over an infinite field k. For example, every Azumaya R-algebra of degree…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3188:field_when:0:2
SUMMARY:The shift action on independent random variables
DTSTART:2021-03-07T10:00:00
DTEND:2021-03-07T11:00:00
DSCRIPTION:Speaker: Zemer Kosloff, Hebrew University of Jerusalem\n
Abstract:
The Bernoulli shift model which is the action on a sequence of i.i.d. random variables by time shifts in one of the central examples of classical ergodic theory. To this date much is known on the ergodic theoretic properties of this model. A notable example is Sinai factor theorem which says that if a given system has positive entropy (is chaotic) then it has Bernoulli shift models as factors (subsystems) which leads to one of the most common definitions of chaos. In addition,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3186:field_when:0:3
SUMMARY:Stationary reflection and Prikry forcing, part 1
DTSTART:2021-03-03T12:00:00
DTEND:2021-03-03T14:00:00
DSCRIPTION:Speaker: Yair Hayut (HUJI)\n
Abstract:
In 1982, Magidor proved the consistency of stationary reflection at \aleph_{\omega+1}, relative to an \omega-sequence of supercompact cardinals.
Square based heuristics indicated that a much weaker large cardinal hypothesis is the correct strength.
In a sequence of results of various authors, Magidor's result was gradually improved to stationary reflection at all sets except one "bad" stationary set at \aleph_{\omega+1}, starting with a large cardinal property weaker than \…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3180:field_when:0:4
SUMMARY:All colorings are strong, but some colorings are stronger than the others
DTSTART:2021-02-24T12:00:00
DTEND:2021-02-24T14:00:00
DSCRIPTION:Speaker: Assaf Rinot (BIU)\n
Abstract:
Strong colorings are everywhere - they can be obtained from analysis of basis problems, transfinite diagonalizations, oscillations, or walks on ordinals. They give rise to interesting topological spaces and partial orders.
In this talk, I'll be looking at all aspects mentioned above, reporting on findings from my joint projects with Kojman, Lambie-Hanson, Inamdar, Steprans and Zhang.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3184:field_when:0:5
SUMMARY:Hasse-Schmidt derivations on Grassmann semi-algebras
DTSTART:2021-02-24T08:30:00
DTEND:2021-02-24T09:30:00
DSCRIPTION:Speaker: Prof. Letterio Gatto (Politecnico di Torino)\n
Abstract:
The talk will be split into two parts. The first will be about the notion of Hasse-Schmidt derivation on a classical exterior algebra, which I introduced years ago to deal with Schubert calculus for complex Grassmannians. In this first part, I will focus on the purely combinatorial features of the construction suited to be transferred in the second part of the talk, concerned with some joint work in progress with Louis Rowen and Adam Chapman. The new framework will be the more general…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3182:field_when:0:6
SUMMARY:The spectra of cardinalities of branches of Kurepa trees, part 2
DTSTART:2021-02-17T12:00:00
DTEND:2021-02-17T14:00:00
DSCRIPTION:Speaker: Mark Poor (HUJI)\n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3181:field_when:0:7
SUMMARY:The spectra of cardinalities of branches of Kurepa trees, part 1
DTSTART:2021-02-10T12:00:00
DTEND:2021-02-10T14:00:00
DSCRIPTION:Speaker: Mark Poor (HUJI)\n
Abstract:
We study the possible values of the Kurepa spectra, i.e. how the set of cardinalities of branches of Kurepa trees may look like. It turns out that assuming GCH below the second uncountable cardinal (and possibly the existence of an inaccessible) we can force every set of cardinals (satisfying some obvious necessary conditions) to be the Kurepa spectrum.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3177:field_when:0:8
SUMMARY:Fresh subsets of measurable ultrapowers
DTSTART:2021-01-27T12:00:00
DTEND:2021-01-27T14:00:00
DSCRIPTION:Speaker: Philip Luecke (Barcelona)\n
Abstract:
In my talk, I want to present recent results studying the closure
and non-closure properties of measurable ultrapowers with respect to Hamkin's
notion of freshness. These results show that the extent of these properties
highly depends on the combinatorics of the underlying model of set theory.
While a result of Sakai shows that it is possible to obtain ultrapowers with
maximal closure properties by forcing over a model containing a strongly com-
pact cardinal, it turns out that…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3176:field_when:0:9
SUMMARY:Lafforgue pseudocharacters and the construction of Galois representations
DTSTART:2021-01-20T08:30:00
DTEND:2021-01-20T09:30:00
DSCRIPTION:Speaker: Dr. Ariel Weiss (Hebrew University of Jerusalem)\n
Abstract:
A key goal of the Langlands program is to attach Galois representations to automorphic representations. In general, there are two methods to construct these representations. The first, and the most effective, is to extract the Galois representation from the étale cohomology of a suitable Shimura variety. However, most Galois representations cannot be constructed in this way. The second, more general, method is to construct the Galois representation, via its corresponding…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3175:field_when:0:10
SUMMARY:Graphs of bounded shrub-depth, through a logic lens
DTSTART:2021-01-17T12:00:00
DTEND:2021-01-17T13:30:00
DSCRIPTION:Speaker: Yijia Chen (Fudan University)\n
Abstract:
Shrub-depth is a graph invariant often considered as an extension of tree-depth to dense graphs. In this talk I will explain our recent proofs of two results about graphs of bounded shrub-depth.
1. Every graph property definable in monadic-second order logic, e.g., 3-colorability, can be evaluated by Boolean circuits of constant depth and polynomial size, whose depth only depends on the shrub-depth of input graphs.
2. Graphs of bounded shrub-depth can be characterized by a finite set…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3173:field_when:0:11
SUMMARY:Universal functions, strong colourings and ideas from PID
DTSTART:2021-01-13T12:00:00
DTEND:2021-01-13T14:00:00
DSCRIPTION:Speaker: Juris Stperans (York)\n
Abstract:
A construction of Shelah will be reformulated using the PID to provide alternative models of the failure of CH and the existence of a universal colouring of cardinality . The impact of the range of the colourings will be examined. An application to the theory of strong colourings over partitions will also be given.
Links to the recording.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3172:field_when:0:12
SUMMARY:On the distribution of randomly signed sums and Tomaszewski’s conjecture
DTSTART:2021-01-10T12:00:00
DTEND:2021-01-10T13:30:00
DSCRIPTION:Speaker: Ohad Klein (Bar-Ilan University)\n
Abstract:
A Rademacher sum X is a random variable characterized by real numbers a_1, ..., a_n, and is equal to
X = a_1 x_1 + ... + a_n x_n,
where x_1, ..., x_n are independent signs (uniformly selected from {-1, 1}).
We discuss various aspects in which Rademacher sums behave "somewhat" like normally distributed variables.
A relevant puzzle by Bogusław Tomaszewski, 1986:
Is it true that all Rademacher sums X satisfy Pr[ |X| <= sqrt Var(X) ] >= 1/2 ?
(for normally distributed variables…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3169:field_when:0:13
SUMMARY:Equations of Modular Curves
DTSTART:2021-01-06T14:00:00
DTEND:2021-01-06T15:00:00
DSCRIPTION:Speaker: Eran Assaf, Dartmouth College\n
Abstract:
Modular curves are fundamental objects in modern number theory, which allow us to relate geometric objects and arithmetic ones. Recent advances towards long standing conjectures depend crucially on explicit computation of these objects. The talk will describe novel algorithms that achieve this goal.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3170:field_when:0:14
SUMMARY:Covering convex regions with unit discs
DTSTART:2021-01-03T12:00:00
DTEND:2021-01-03T13:30:00
DSCRIPTION:Speaker: Simi Haber (Bar-Ilan University)\n
Abstract:
Given a convex region C in the plane, how many unit discs are needed to cover it? This classic discrete geometry problem has real life applications in, e.g., placing cellular antennas.
A precise answer for the above question seems out of reach, even when C is a disc of a given radius. However, Blaschke, Toth and Hadwiger provided a nonconstructive upper bound for the number of required discs, as a function of the area and perimeter of C.
In this talk we will discuss an improved…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3174:field_when:0:15
SUMMARY:Actions of tame abelian product groups
DTSTART:2020-12-30T12:00:00
DTEND:2020-12-30T14:00:00
DSCRIPTION:Speaker: Assaf Shani (Harvard)\n
Abstract:
A Polish group G is tame if for any continuous action of G, the corresponding orbit equivalence relation is Borel. Suppose that G=\prod_n \Gamma_n is a product of countable abelian groups. It follows from results of Solecki and Ding-Gao that if G is tame, then all of its actions are in fact potentially \Pi^0_6. Ding and Gao conjectured that this bound could be improved to \Pi^0_3. We refute this, by finding an action of a tame abelian product group, which is not potentially \Pi^0_5.…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3168:field_when:0:16
SUMMARY:Minimal forms for conics
DTSTART:2020-12-30T08:30:00
DTEND:2020-12-30T09:30:00
DSCRIPTION:Speaker: Dr. Adam Chapman (Academic College of Tel Aviv-Yafo)\n
Abstract:
A conic is the Severi-Brauer variety of a quaternion algebra Q, and the question of which anisotropic quadratic forms become isotropic over the function field F_Q of a conic has puzzled algebraists for the last three decades. An anisotropic quadratic form is F_Q-minimal if it becomes isotropic over F_Q but any proper subform remains anisotropic. Minimal forms are known to have odd dimension, and examples of minimal forms of any odd dimension were constructed by Hoffmann and Van Geel…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3167:field_when:0:17
SUMMARY:Hyperpaths
DTSTART:2020-12-27T12:00:00
DTEND:2020-12-27T13:30:00
DSCRIPTION:Speaker: Amir Dahari (Hebrew University of Jerusalem)\n
Abstract:
Hypertrees are high-dimensional counterparts of graph theoretic trees. They have attracted a great deal of attention by various investigators.
Here we introduce and study {\em Hyperpaths} - a particular class of hypertrees which are high dimensional analogs of paths in graph theory. A $d$-dimensional hyperpath is a $d$-dimensional hypertree in which every $(d-1)$-dimensional face is contained…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3166:field_when:0:18
SUMMARY:S spaces and L spaces, part 2
DTSTART:2020-12-23T12:00:00
DTEND:2020-12-23T14:00:00
DSCRIPTION:Speaker: Roy Shalev (BIU)\n
Abstract:
We introduce a new combinatorial principle which we call ♣_AD. This principle asserts the existence of a certain multi-ladder system with guessing and almost-disjointness features, and is shown to be sufficient for carrying out de Caux type constructions of topological spaces.
Our main result states that strong instances of ♣_AD follow from the existence of a Souslin tree. As an application, we obtain a simple, de Caux type proof of Rudin’s result that if there is a Souslin tree,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3165:field_when:0:19
SUMMARY:Representability and boxicity of simplicial complexes
DTSTART:2020-12-20T12:00:00
DTEND:2020-12-20T13:30:33
DSCRIPTION:Speaker: Alan Lew (Technion)\n
Abstract:
An interval graph is the intersection graph of a family of intervals in the real line. Motivated by problems in ecology, Roberts defined the boxicity of a graph G to be the minimal k such that G can be written as the intersection of k interval graphs.
A natural higher dimensional generalization of interval graphs is the class of d-representable complexes. These are simplicial complexes that carry the information on the intersection patterns of a family of convex sets in R^d. We…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3164:field_when:0:20
SUMMARY:Classification results in equivariant symplectic geometry
DTSTART:2020-12-20T10:00:00
DTEND:2020-12-20T11:00:00
DSCRIPTION:Speaker: Yael Karshon, University of Toronto\n
Abstract:
I will report on some old and new classification results in
equivariant symplectic geometry, including my classification, joint with
Sue Tolman, of Hamiltonian torus actions with two dimensional quotients.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3162:field_when:0:21
SUMMARY:Phase retrieval stability via notions of graph connectivity
DTSTART:2020-12-16T13:00:00
DTEND:2020-12-16T14:00:00
DSCRIPTION:Speaker: Nadav Dym (Duke University)\n
Abstract:
Phase retrieval is the inverse problem of reconstructing a signal from linear measurements, when the phase of the measurements is lost and only the magnitude is known. This problem occurs in many applications including crystallography, optics, and acoustics.
In the talk I will discuss results on invertibility and stability of phase retrieval. I will focus on a recent paradigm which characterizes phase retrieval stability via appropriate notions of graph connectivity, and in…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3163:field_when:0:22
SUMMARY:S spaces and L spaces, part 1
DTSTART:2020-12-16T12:00:00
DTEND:2020-12-16T14:00:00
DSCRIPTION:Speaker: Roy Shalev (BIU)\n
Abstract:
An S-space is a regular topological space that is hereditarily separable but not Lindel\"of. An L-space is a regular topological space that is hereditarily Lindel\"of but not separable. We will survey the history behind the question of their existence and present some constructions
END:VEVENT
BEGIN:VEVENT
UID:calendar:3158:field_when:0:23
SUMMARY:Rationality of representation zeta functions of compact p-adic analytic groups
DTSTART:2020-12-16T09:00:00
DTEND:2020-12-16T10:00:00
DSCRIPTION:Speaker: Prof. Alexander Stasinski (University of Durham)\n
Abstract:
A representation zeta function of a group G is a (meromorphic continuation of) a Dirichlet series in a complex variable s whose n-th coefficient is the number of irreducible representations of dimension n of G (supposing that these numbers are finite). In 2006 Jaikin-Zapirain proved one of the most fundamental results in the area, namely that if G is a FAb compact p-adic analytic group (e.g., SL_n(Z_p)) and p > 2, then the representation zeta function of G is "virtually rational"…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3156:field_when:0:24
SUMMARY:The Worpitzky identity for the groups of signed and even-signed permutations
DTSTART:2020-12-06T12:00:00
DTEND:2020-12-06T13:30:00
DSCRIPTION:Speaker: Eli Bagno (Jerusalem College of Technology)\n
Abstract:
The well-known Worpitzky identity provides a connection between two bases of : The standard basis and the binomial basis , where the Eulerian numbers for the Coxeter group of type (the symmetric group) serve as the entries of the transformation matrix.
Brenti has generalized this identity to the Coxeter groups of types and (signed and even-signed permutations groups, respectively) using generatingfunctionology.
Motivated by Foata-Schützenberger and Rawlings' proof for the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3157:field_when:0:25
SUMMARY:Model Theoretic Classification and its Applications to Algebra
DTSTART:2020-12-06T10:00:00
DTEND:2020-12-06T11:00:00
DSCRIPTION:Speaker: Yatir Halevi (Ben Gurion University)\n
Abstract:
Classification theory is a program initiated by Shelah in the early 70s with the aim of classifying complete first order theories into "tame" and "wild" theories by some relatively simple combinatorial invariants. Examples of such theories are stable, dependent and simple theories.
From the beginning, the applications stemming from this work moved in two intertwining directions.
The first, a detailed study of the geometry arising in such theories and applying these notions to…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3155:field_when:0:26
SUMMARY:Woodin Extender Algebra and its applications for absoluteness, part 2
DTSTART:2020-12-02T12:00:00
DTEND:2020-12-02T14:00:00
DSCRIPTION:Speaker: Menachem Magidor (HUJI)\n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3148:field_when:0:27
SUMMARY:A freeness criterion without patching for modules over local rings
DTSTART:2020-12-02T08:30:00
DTEND:2020-12-02T09:30:00
DSCRIPTION:Speaker: Dr. Sylvain Brochard (Montpellier)\n
Abstract:
Let A->B be a local homomorphism of (commutative) Noetherian local rings. Bart de Smit conjectured in the late 1990's that if A and B have the same embedding dimension, then any finitely generated B-module that is flat over A, is flat over B. This conjecture was proved in 2017 and allows one in some situations to dispense with patching in the techniques à la Wiles to prove modularity lifting theorems (e.g. in the proof of FLT). We generalize this result as follows: if M is a…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3150:field_when:0:28
SUMMARY:Random permutations sampled by surface groups
DTSTART:2020-11-29T12:00:00
DTEND:2020-11-29T13:30:00
DSCRIPTION:Speaker: Doron Puder (Tel-Aviv University)\n
Abstract:
Let be the fundamental group of the closed orientable surface of genus , namely, . Fix an element and let be a uniformly random homomorphism to the symmetric group .
We develop new techniques to study the random permutation , and derive several results which are analogous to well-known results when is replaced with a free group.
This is joint work with Michael Magee.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3149:field_when:0:29
SUMMARY:Pattern Statistics in Permutations and Words
DTSTART:2020-11-29T10:00:00
DTEND:2020-11-29T11:00:00
DSCRIPTION:Speaker: Chaim Even-Zohar (The Alan Turing Institute, London)\n
Abstract:
Patterns in a large combinatorial structure, such as a graph, a word, or a permutation, are the induced substructures on small subsets of vertices or entries. If a permutation describes the relation between the y-ranks and x-ranks of n points in the xy-plane, then every subset of k points induces one of k! possible patterns. Similarly, in an n-letter word over a finite alphabet, every k positions induce a k-letter subword. Some important questions are: How frequently does each pattern…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3147:field_when:0:30
SUMMARY:Woodin Extender Algebra and its applications for absoluteness, part 1
DTSTART:2020-11-25T12:00:00
DTEND:2020-11-25T14:00:00
DSCRIPTION:Speaker: Menachem Magidor (HUJI)\n
Abstract:
This talk will survey known results and will be the first of several talks which will not necessarily follow in the consecutive weeks.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3145:field_when:0:31
SUMMARY:Generalized permutations related to degenerate Eulerian numbers
DTSTART:2020-11-22T12:00:00
DTEND:2020-11-22T13:30:00
DSCRIPTION:Speaker: Orli Herscovici (University of Haifa)\n
Abstract:
Carlitz (1979) defined degenerate Eulerian polynomials and numbers; however, there is no publication describing their combinatorial aspects.
In this talk we consider a combinatorial model that generalizes the standard definition of permutations and provides missing combinatorial proofs for some relations on degenerate Eulerian numbers…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3142:field_when:0:32
SUMMARY:Existence of Equilibrium in Repeated Blackwell Games when the Payoff is Tail Measurable
DTSTART:2020-11-22T10:00:00
DTEND:2020-11-22T11:00:00
DSCRIPTION:Speaker: Galit Ashkenazi-Golan\n
Abstract:
We prove the existence of equilibrium in repeated Blackwell games with Borel tail-measurable winning sets, and with Borel tail-measurable payoffs. The proof uses a regularity result of the minmax value
END:VEVENT
BEGIN:VEVENT
UID:calendar:3141:field_when:0:33
SUMMARY:Estimation of Manifolds from Point Clouds: Building Models from Data
DTSTART:2020-11-18T14:00:00
DTEND:2020-11-18T15:00:00
DSCRIPTION:Speaker: Barak Sober (Duke University)\n
Abstract:
A common observation in data-driven applications is that high dimensional data has a low intrinsic dimension, at least locally. Thus, when one wishes to work with data that is not governed by a clear set of equations, but still wishes to perform statistical or other scientific analysis, an optional model is the assumption of an underlying manifold from which the data was sampled. This manifold, however, is not given explicitly but we can obtain samples of it (i.e., the individual data…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3144:field_when:0:34
SUMMARY:Independent families in the countable and the uncountable
DTSTART:2020-11-18T12:00:00
DTEND:2020-11-18T14:00:00
DSCRIPTION:Speaker: Vera Fischer (Vienna)\n
Abstract:
Independent families on $\omega$ are families of infinite sets of integers with the property that for any two finite subfamilies $A$ and $B$ the set $\bigcap A\backslash \bigcup B$ is infinite. Of particular interest are the sets of the possible cardinalities of maximal independent families, which we refer to as the spectrum of independence. Even though we do have the tools to control the spectrum of independence at $\omega$ (at least to a large extent), there are many relevant…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3135:field_when:0:35
SUMMARY:The congruence kernel problem for endomorphism rings
DTSTART:2020-11-18T08:30:00
DTEND:2020-11-18T09:30:00
DSCRIPTION:Speaker: Tamar Bar-On (Bar-Ilan University)\n
Abstract:
We present the congruence kernel problem for endomorphism rings of finitely generated projective modules, and give it a positive answer in the case of faithful modules over commutative rings.
=================================================
Michael Schein is inviting you to a scheduled Zoom meeting.
Topic: Bar-Ilan Algebra Seminar -- Bar-On
Time: Nov 18, 2020 10:30 AM Jerusalem
Join Zoom Meeting
https://us02web.zoom.us/j/88355947298?pwd=bFZvU2xqand4dXdEaDNoUnBJdHVUd…
Meeting ID…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3139:field_when:0:36
SUMMARY:The resonance arrangement
DTSTART:2020-11-15T12:00:00
DTEND:2020-11-15T13:30:00
DSCRIPTION:Speaker: Lukas Kühne (Max Planck Institute, Leipzig)\n
Abstract:
The resonance arrangement is the arrangement of hyperplanes which has all nonzero 0/1-vectors in R^n as normal vectors. It is also called the all-subsets arrangement. Its chambers appear in algebraic geometry, in mathematical physics, and as maximal unbalanced families in economics.
In this talk, I will present a universality result of the resonance arrangement. Subsequently, I will report on partial progress on counting its chambers. Along the way, I will review some basics of the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3138:field_when:0:37
SUMMARY:Stationary random entire functions and related questions
DTSTART:2020-11-11T14:00:00
DTEND:2020-11-11T15:00:00
DSCRIPTION:Speaker: Adi Glucksam (University of Toronto)\n
Abstract:
Let T be the action of the complex plane on the space of entire functions defined by translations, i.e T_w takes the entire function f(z) to the entire function f(z+w). B.Weiss showed in `97 that there exists a probability measure defined on the space of entire functions, which is invariant under this action. In this talk I will present optimal bounds on the minimal possible growth of functions in the support of such measures, and discuss other growth related problems inspired by this…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3143:field_when:0:38
SUMMARY:Higher Chang Conjecture, part 2
DTSTART:2020-11-11T12:00:00
DTEND:2020-11-11T14:00:00
DSCRIPTION:Speaker: Yait Hayut (HUJI)\n
Abstract:
Here is the recording
END:VEVENT
BEGIN:VEVENT
UID:calendar:3136:field_when:0:39
SUMMARY:Construction of quasi-morphisms on groups of measure-preserving homeomorphisms of non-orientable surfaces
DTSTART:2020-11-10T09:30:00
DTEND:2020-11-10T10:30:00
DSCRIPTION:Speaker: Rishi Kumar, BGU\n
Abstract:
A quasi-morphism on a group G is a real-valued function which satisfies the homomorphism equation up to a bounded error. Let Ng be a non-orientable surface of genus g≥ 3 and let Homeo0(Ng,μ) be the identity component of the group of measure-preserving homeomorphisms of Ng.
We prove that the space of homogeneous quasi-morphisms on the group Homeo0(Ng,μ) is infinite-dimensional. This project is part of an M.Sc. thesis under the supervision of Dr. Brandenbursky.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3133:field_when:0:40
SUMMARY:An identity of permutation statistics on the hyperoctahedral group
DTSTART:2020-11-08T12:00:00
DTEND:2020-11-08T13:30:00
DSCRIPTION:Speaker: Michael Schein (Bar-Ilan University)\n
Abstract:
We define a statistic on the hyperoctahedral group B_n; this is a special case of one introduced by Stembridge and Waugh. We show that a certain two-variable generating function involving this statistic factors into the product of a generating function over the symmetric group S_n and some simple binomials. Then we mention related results by Macdonald and Carnevale-Shechter-Voll, and discuss what the correct way to state and prove our identity should be.
Our motivation for this…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3134:field_when:0:41
SUMMARY:Rough walks
DTSTART:2020-11-08T10:00:00
DTEND:2020-11-08T11:00:00
DSCRIPTION:Speaker: Tal Orenshtein (Technical University of Berlin and Weierstrass Institute)\n
Abstract:
Random walks in random environment (RWRE) have been extensively studied in the last half-century. Two prototypical cases are the reversible and the ballistic classes and even though they are fundamentally different, functional central limit theorems (FCLT) are known to hold in both. This is done using rather different techniques; Kipnis-Varadhan's theory for additive functional of Markov processes is applicable in the reversible case while for the ballistic class the main feature is a…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3131:field_when:0:42
SUMMARY:Lie superalgebras, an introductory talk
DTSTART:2020-11-04T16:30:00
DTEND:2020-11-04T17:30:00
DSCRIPTION:Speaker: Maria Gorelik, WIS\n
Abstract:
This is the first lecture of STARS (Superalgebra Theory and Representations Seminar) series.
Meeting ID: 919 8455 8186
Password: 663945https://weizmann.zoom.us/j/91984558186?pwd=dzl2Z2hPRWtzaDF6R1pySXd4OGFIQT09
END:VEVENT
BEGIN:VEVENT
UID:calendar:3130:field_when:0:43
SUMMARY:Recent Progress on the Exact Overlaps Conjecture
DTSTART:2020-11-04T14:00:00
DTEND:2020-11-04T15:00:00
DSCRIPTION:Speaker: Ariel Rapaport (University of Cambridge)\n
Abstract:
A well known conjecture in fractal geometry says that the dimension of a self-similar measure is strictly smaller than its natural upper bound only in the presence of exact overlaps. That is, only if the maps in the generating iterated function system do not generate a free semigroup. I will present recent developments regarding this conjecture, focusing on my joint work with P. Varjú regarding homogeneous systems of three maps
END:VEVENT
BEGIN:VEVENT
UID:calendar:3132:field_when:0:44
SUMMARY:Higher Chang Conjecture
DTSTART:2020-11-04T12:00:00
DTEND:2020-11-04T14:00:00
DSCRIPTION:Speaker: Yait Hayut (HUJI)\n
Abstract:
In this talk I will present some results regarding the consistency strength of Higher variants of Chang's Conjecture.
I will start with the classical result by Silver of Chang's Conjecture from $\omega_1$-Erdos cardinal.
Then, I will give an upper bound for the consistency strength of $(\aleph_{\omega+1}, \aleph_{\omega}) -->>(\aleph_1, \aleph_0)$
and $(\aleph_4, \aleph_3) -->> (\aleph_2, \aleph_1)$ (joint with Eskew)
from supercompactness assumptions.
If time…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3127:field_when:0:45
SUMMARY:Automorphism groups, elliptic curves, and the PORC conjecture
DTSTART:2020-11-04T08:30:00
DTEND:2020-11-04T09:30:00
DSCRIPTION:Speaker: Dr. Mima Stanojkovski (Leipzig)\n
Abstract:
In 1960, Graham Higman formulated his famous PORC conjecture in relation to the function f(p,n) counting the isomorphism classes of p-groups of order p^n . By means of explicit formulas, the PORC conjecture has been verified for n < 8. Despite that, it is still open and has in recent years been questioned. I will discuss (generalizations of) an example of du Sautoy and Vaughan-Lee (2012), together with a conceptualization of the phenomena they observe. Hidden heroes of this story…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3129:field_when:0:46
SUMMARY:From fractional to integral matchings in d-partite hypergraphs
DTSTART:2020-11-01T12:00:00
DTEND:2020-11-01T13:30:00
DSCRIPTION:Speaker: Erel Segal-Halevi (Ariel University)\n
Abstract:
A d-partite hypergraph is called *fractionally balanced* if there exists a non-negative function on its edge set that has constant degrees in each vertex side. Using a topological version of Hall's theorem, we prove new lower bounds on the matching number of such hypergraphs. Our bounds yield results on envy-free division of multiple cakes, covering colorful families of d-intervals, and rental harmony with multiple houses.
Joint work with Ron Aharoni, Eli Berger, Joseph Briggs and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3128:field_when:0:47
SUMMARY:On Continuous Tree-Like Scales and related properties of Internally Approachable structures
DTSTART:2020-10-28T12:00:00
DTEND:2020-10-28T14:00:00
DSCRIPTION:Speaker: Omer Ben-Neria (HUJI)\n
Abstract:
In his PhD thesis, Luis Pereira isolated and developed several principles of singular cardinals that emerge from Shelah's PCF theory; principles which involve properties of scales, such as the inexistence of continuous Tree-Like scales, and properties of internally approachable structures such as the Approachable Free Subset Property.
In the talk, we will discuss these principles and their relations, and present new results from a joint work with Dominik Adolf concerning their…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3123:field_when:0:48
SUMMARY:Generalized Brauer dimension and other arithmetic invariants of semi-global fields
DTSTART:2020-10-28T08:30:00
DTEND:2020-10-28T09:30:00
DSCRIPTION:Speaker: Dr. Saurabh Gosavi (Bar-Ilan University)\n
Abstract:
Given a finite set of Brauer classes B of a fixed period \ell, we define eind(B) to be the minimum of degrees of field extensions L/F such that b \otimes_F L = 0 for every b in B. We provide upper bounds for eind(B) which depend on invariants of fields of lower arithmetic complexity, for B in the Brauer group of a semi-global field. As a simple application of our result, we obtain an upper bound for the splitting index of quadratic forms and finiteness of symbol length for function…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3124:field_when:0:49
SUMMARY:Algebraic Structures on Automorphic L-Functions
DTSTART:2020-10-27T09:30:00
DTEND:2020-10-27T10:30:00
DSCRIPTION:Speaker: Gal Dor\n
Abstract:
Consider the function field F of a smooth curve over F_q, with q > 2.
L-functions of automorphic representations of GL(2) over F are important objects for studying the arithmetic properties of the field F. Unfortunately, they can be defined in two different ways: one by Godement-Jacquet, and one by Jacquet-Langlands. Classically, one shows that the resulting L-functions coincide using a complicated computation.
I will present a conceptual proof that the two families coincide…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3125:field_when:0:50
SUMMARY:On the Stanley-Wilf limit of the pattern 1324
DTSTART:2020-10-25T12:00:00
DTEND:2020-10-25T13:30:00
DSCRIPTION:Speaker: Toufik Mansour (University of Haifa)\n
Abstract:
We present an explicit formula for the generating function for the number of permutations of length $n$ that avoid $1324$, in terms of generating functions for permutations that have a kernel shape of length $m$, $m \ge 2$. This allows us to write down a systematic procedure for finding a lower bound for approximating the Stanley-Wilf limit of the pattern $1324$.
Joint work with Christian Nassau.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3122:field_when:0:51
SUMMARY:Operator algebraic graph theory
DTSTART:2020-10-25T10:00:00
DTEND:2020-10-25T11:00:00
DSCRIPTION:Speaker: Adam Dor On (University of Copenhagen)\n
Abstract:
The Toeplitz algebra of a directed graph is the norm-closed $*$-algebra generated by edge and vertex concatenation operators on the inner-product space of square summable sequences indexed by finite paths of the graph. A canonical quotient of it is the celebrated Cuntz-Krieger algebra, which is deeply connected to the associated subshift of finite type of the directed graph. Understanding representations of Cuntz-Krieger algebras has become useful for producing wavelet bases on self-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3120:field_when:0:52
SUMMARY:Local club condensation in extender models
DTSTART:2020-10-22T07:00:00
DTEND:2020-10-22T09:00:00
DSCRIPTION:Speaker: Gabriel Fernandes (BIU)\n
Abstract:
Local club condensation is an abstraction of the condensation properties of the constructible hierarchy.
We will prove that for extender models that are countably iterable, given a cardinal kappa, the J_alpha^{E} hierarchy witnesses local club condensation in the interval (kappa^+,kappa^++) if and only if kappa is not a subcompact cardinal in L[E].
From the above and the equivalence between subcompact cardinals and square, due to Schimmerling and Zeman, it follows that in such…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3126:field_when:0:53
SUMMARY:Equidistribution of mesh patterns of length two and Kitaev and Zhang's conjectures
DTSTART:2020-10-18T11:00:00
DTEND:2020-10-18T12:30:00
DSCRIPTION:Speaker: Bin Han (Bar-Ilan University)\n
Abstract:
A systematic study of avoidance of mesh patterns of length 2 was conducted by Hilmarsson et al. in 2015. In a recent paper, Kitaev and Zhang examined the distribution of the aforementioned patterns.
We show that two pairs of triple mesh patterns are equidistributed, by constructing two involutions on permutations. As an application we confirm four conjectures raised by Kitaev and Zhang recently.
Based on joint work with Jiang Zeng.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3121:field_when:0:54
SUMMARY:Triples and systems: a general algebraic structure theory applicable to tropical mathematics
DTSTART:2020-10-18T09:00:00
DTEND:2020-10-18T10:00:00
DSCRIPTION:Speaker: Louis Rowen (Bar-Ilan University)\n
Abstract:
Our goal is to present an axiomatic algebraic theory which unifies
and “explains” aspects of tropical algebra, hyperfields, and fuzzy rings in terms
of classical algebraic concepts, especially negation, which may not exist a priori.
It was motivated by an attempt to understand whether or not it is coincidental
that basic algebraic theorems are mirrored in supertropical algebra, and was
spurred by the realization that some of the same results are obtained in parallel
research on…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3118:field_when:0:55
SUMMARY:Coloring Superstable Graphs
DTSTART:2020-10-12T08:00:00
DTEND:2020-10-12T10:00:00
DSCRIPTION:Speaker: Yatir Halevi (BGU)\n
Abstract:
Given a graph G=(V,E), a coloring of G in \kappa colors is a map c:V\to \kappa in which adjacent vertices are colored in different colors. The chromatic number of G is the smallest such \kappa.
We will briefly review some questions and conjectures on the chromatic number of infinite graphs and will mainly concentrate on the following strong form of Taylor's conjecture:
If G is an infinite graph with chromatic number\geq \alepha_1 then it contains all finite subgraphs of Sh_n(\omega)…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3101:field_when:0:56
SUMMARY:On the inexistence of Continuous Tree-Like Scales, and the Approachable Free Subset Property
DTSTART:2020-09-14T08:00:00
DTEND:2020-09-14T10:00:00
DSCRIPTION:Speaker: Omer Ben-Neria (HUJI)\n
Abstract:
In his PhD thesis, Luis Pereira has isolated two properties of sequences of regular cardinals (kappa_n)_n from Shelah's PCF theory, which are related to the possible consistency of 2^{aleph_omega} being greater or equal to aleph_{omega_1}, when aleph_omega is a strong limit cardinal.
The first property is the inexistence of a continuous tree-like scale on the product of regular cardinals kappa_n, n < omega. A scale <f_alpha : alpha < lambda> is said to be tree-like if for…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3100:field_when:0:57
SUMMARY:Jensen's covering theorem for L
DTSTART:2020-08-31T08:00:00
DTEND:2020-08-31T10:00:00
DSCRIPTION:Speaker: Gabriel Fernandes (BIU)\n
Abstract:
Jensen's covering theorem for Godel's constructible universe, L, says that if there is no non-trivial elementary embedding from L into L, then for every uncountable set of ordinals, X, there is a set, Y, such that Y is an element of L, |X| = |Y| and X is a subset of Y.
We will sketch the proof of the covering lemma for L.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3099:field_when:0:58
SUMMARY:Weak diamond, Uniformization and its connection to Whitehead's problem
DTSTART:2020-08-26T08:00:00
DTEND:2020-08-26T10:00:00
DSCRIPTION:Speaker: Menachem Magidor (HUJI)\n
Abstract:
I'll speak and I'll present some old results about weak diamond, uniformization and maybe some connections to Whitehead problem. In particular I'll present Woodin's elegant proof to the Devlin-Shelah equivalence of Weak diamond with 2^\aleph_0<2^\aleph_1.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3096:field_when:0:59
SUMMARY:Explicit Serre weights for two-dimensional Galois representations
DTSTART:2020-08-26T07:30:00
DTEND:2020-08-26T08:30:00
DSCRIPTION:Speaker: Dr. Misja Steinmetz (Leiden University)\n
Abstract:
The Serre weight conjectures are conjectures that, roughly
speaking, predict the weight of a modular form from which a given mod p
Galois representation arises. Starting from Serre's original conjecture
for classical modular forms, I will give a motivated approach towards
correct generalisations of the Serre weight conjectures to Hilbert
modular forms. Then I'll talk about new results giving a more explicit
version of the weight conjectures for Hilbert modular forms…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3098:field_when:0:60
SUMMARY:Square of Menger groups
DTSTART:2020-08-24T08:00:00
DTEND:2020-08-24T10:00:00
DSCRIPTION:Speaker: Jialiang He (BIU)\n
Abstract:
This work is cooperated with Yinhe Peng and Liuzhen Wu.
I will present a few constructions for square of Menger group problem in metrizable sense and generally sense in this talk.
Under cov(M)=c, for any n\geq 1, there is a subgroup G of Z^N such that G^n is Menger but G^{n+1} is not Menger.
Under cov(M)=d=cf(d)$, for any n\geq 1, there is a subgroup G of R such that G^n is Menger but G^{n+1} is not Menger.
For any n\geq 1, There is a Menger subgroup G of R^{\…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3097:field_when:0:61
SUMMARY:Coding well ordering of the reals with ladders, part 5
DTSTART:2020-08-19T08:00:00
DTEND:2020-08-19T10:00:00
DSCRIPTION:Speaker: Uri Abraham (BGU) \n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3010:field_when:0:62
SUMMARY:Non-admissible modulo p representations of GL_2(Q_{p^2})
DTSTART:2020-08-19T07:30:00
DTEND:2020-08-19T08:30:00
DSCRIPTION:Speaker: Prof. Eknath Ghate (Tata Institute of Fundamental Research, Mumbai)\n
Abstract:
The notion of admissibility of representations of p-adic groups
goes back to Harish-Chandra. Jacquet and Vigneras have shown that
smooth irreducible representations of connected reductive p-adic
groups over algebraically closed fields of characteristic different
from p are admissible.
The smooth irreducible representations of $\mathrm{GL}_2({\mathbb Q}_p)$
over $\bar{\mathbb F}_p$ are also known to be admissible, by the
work of Barthel-Livne, Breuil and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:3094:field_when:0:63
SUMMARY:Fedorchuck's space, part 2
DTSTART:2020-08-17T08:00:00
DTEND:2020-08-17T10:00:00
DSCRIPTION:Speaker: Roy Shalev (BIU)\n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3093:field_when:0:64
SUMMARY:Coding well ordering of the reals with ladders, part 4
DTSTART:2020-08-12T08:00:00
DTEND:2020-08-12T10:00:00
DSCRIPTION:Speaker: Uri Abraham (BGU) \n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3092:field_when:0:65
SUMMARY:Chang's conjecture, part 2
DTSTART:2020-08-10T08:00:00
DTEND:2020-08-10T10:00:00
DSCRIPTION:Speaker: Jing Zhang (BIU)\n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3012:field_when:0:66
SUMMARY:Coding well ordering of the reals with ladders, part 3
DTSTART:2020-08-05T08:00:00
DTEND:2020-08-05T10:00:00
DSCRIPTION:Speaker: Uri Abraham (BGU) \n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3091:field_when:0:67
SUMMARY:Chang's conjecture, part 1
DTSTART:2020-08-03T08:00:00
DTEND:2020-08-03T10:00:00
DSCRIPTION:Speaker: Jing Zhang (BIU)\n
Abstract:
We'll talk about colorings of triples of w2
END:VEVENT
BEGIN:VEVENT
UID:calendar:3009:field_when:0:68
SUMMARY:Fedorchuck's space, part 1
DTSTART:2020-07-27T08:00:00
DTEND:2020-07-27T10:00:00
DSCRIPTION:Speaker: Roy Shalev\n
Abstract:
We shall present Fedorchuck's construction of a compact S-space of size 2^{w1}. If time permits, we shall show how it connects with the Moore-Mrowka problem.
END:VEVENT
BEGIN:VEVENT
UID:calendar:3007:field_when:0:69
SUMMARY:Coding well ordering of the reals with ladders, part 2
DTSTART:2020-07-22T08:00:00
DTEND:2020-07-22T10:00:00
DSCRIPTION:Speaker: Uri Abraham (BGU) \n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3008:field_when:0:70
SUMMARY:A Partition Theorem for Scattered Order Types, part 2
DTSTART:2020-07-20T08:00:00
DTEND:2020-07-20T10:00:00
DSCRIPTION:Speaker: Tanmay Inamdar (BIU) \n
Abstract:
we continue
END:VEVENT
BEGIN:VEVENT
UID:calendar:3006:field_when:0:71
SUMMARY:Coding well ordering of the reals with ladders, part 1
DTSTART:2020-07-15T08:00:00
DTEND:2020-07-15T10:00:00
DSCRIPTION:Speaker: Uri Abraham (BGU)\n
Abstract:
Results from the 2002 paper "Coding with Ladders a Well Ordering of the Reals" by Abraham and Shelah.
Recoding is now available.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2999:field_when:0:72
SUMMARY:A Partition Theorem for Scattered Order Types, part 1
DTSTART:2020-07-13T08:00:00
DTEND:2020-07-13T10:00:00
DSCRIPTION:Speaker: Tanmay Inamdar (BIU)\n
Abstract:
I will talk about the titular paper by Komjath and Shelah. It is a short paper.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2996:field_when:0:73
SUMMARY:The tree property at Aleph_{w+1}
DTSTART:2020-07-01T08:00:00
DTEND:2020-07-01T10:00:00
DSCRIPTION:Speaker: Tzoor Plotnikov (HUJI)\n
Abstract:
Covering Neeman's proof
END:VEVENT
BEGIN:VEVENT
UID:calendar:2995:field_when:0:74
SUMMARY:On the free subset number of a topological space and their G_\delta modification
DTSTART:2020-06-24T08:00:00
DTEND:2020-06-24T10:00:00
DSCRIPTION:Speaker: Istvan Juhasz (Renyi Institute)\n
Abstract:
Attached
END:VEVENT
BEGIN:VEVENT
UID:calendar:2994:field_when:0:75
SUMMARY:Wide Aronszajn trees
DTSTART:2020-06-17T08:00:00
DTEND:2020-06-17T10:00:00
DSCRIPTION:Speaker: Mirna Dzamonja (UEA)\n
Abstract:
A wide Aronszajn tree is a tree is size and height omega_1 but with no uncountable branch. Such trees arise naturally in the study of model-theoretic notions on models of size aleph_1 as well as in generalised descriptive set theory. In their 1994 paper devoted to various aspects of such trees, Mekler and Väänänen studied the so called weak embeddings between such trees, which are simply defined as strict-order preserving functions. Their work raised the question if under MA there…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2993:field_when:0:76
SUMMARY:Tameness in Set Theory
DTSTART:2020-06-10T08:00:00
DTEND:2020-06-10T10:00:00
DSCRIPTION:Speaker: Matteo Viale (Torino)\n
Abstract:
We show that (assuming large cardinals) set theory is a tractable (and we dare to say tame) first order theory when formalized in a first order signature with natural predicate symbols for the basic definable concepts of second and third order arithmetic, and appealing to the model-theoretic notions of model completeness and model companionship.
Specifically we develop a general framework linking generic absoluteness results to model companionship and show that (with the required…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2939:field_when:0:77
SUMMARY:Prof. Nathalie Q. Balaban - TBA
DTSTART:2020-06-04T11:00:00
DTEND:2020-06-04T12:00:00
DSCRIPTION:Speaker: Prof. Nathalie Q. Balaban\n
Abstract:
TBA
END:VEVENT
BEGIN:VEVENT
UID:calendar:2988:field_when:0:78
SUMMARY:BPFA and Delta_1-definablity of NS_{w1}
DTSTART:2020-06-03T08:00:00
DTEND:2020-06-03T10:00:00
DSCRIPTION:Speaker: Liuzhen Wu (Chinese Acad. Sciences, Beijing)\n
Abstract:
I will discuss a proof of the joint consistency of BPFA and \Delta_1-definablity of NS_{\omega_1}.
Joint work with Stefan Hoffelner and Ralf Schindler.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2987:field_when:0:79
SUMMARY:Filter Reflection
DTSTART:2020-05-27T08:00:00
DTEND:2020-05-27T10:00:00
DSCRIPTION:Speaker: Miguel Moreno (KGRC)\n
Abstract:
Filter reflection is an abstract version of stationary reflection. In this talk we will define filter reflection and different avatars of it. We will show the compatibility with large cardinals, forcing axioms, and V＝L.
We will focus on the case when filter reflection holds and stationary reflaction fails, we will discuss how to force this case.
We will also discuss the failure of filter reflection, how to force the failure and the requierements for it.
If the time allows, some…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2985:field_when:0:80
SUMMARY:Compactness problems for chromatic numbers of graphs
DTSTART:2020-05-20T08:00:00
DTEND:2020-05-20T10:00:00
DSCRIPTION:Speaker: Menachem Magidor (HUJI)\n
Abstract:
I'll speak about compactness problems for chromatic numbers of graphs. The main result will be a some what simplified proof of a theorem by Shelah, that a non reflecting stationary subset of a regular cardinal \lambda S\subseteq S^\lambda_kappa implies (under mild cardinal arithmetic assumptions) that there is a graph of size \lambda with chromatic number lambda , but every smaller cardinality subgraph has chromatic number <=kappa.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2984:field_when:0:81
SUMMARY:Sigma-Prikry forcing, part 2
DTSTART:2020-05-13T08:00:00
DTEND:2020-05-13T10:00:00
DSCRIPTION:Speaker: Alejandro Poveda (Universitat de Barcelona) \n
Abstract:
(joint work with A. Rinot and D. Sinapova)
In the previous talk, we introduced the notion of \Sigma-Prikry forcing and showed that many classical Prikry-type forcing which center on countable cofinalities fall into this framework.
The aim of this talk is to present our iteration scheme for \Sigma-Prikry forcings.
In case time permits, we will also show how to use this general iteration theorem to derive as a corollary the following strengthening of Sharon’s theorem: starting with…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2938:field_when:0:82
SUMMARY:Prof. Yachin Ivry - TBA
DTSTART:2020-05-07T11:00:00
DTEND:2020-05-07T12:00:00
DSCRIPTION:Speaker: Prof. Yachin Ivry\n
Abstract:
TBA
END:VEVENT
BEGIN:VEVENT
UID:calendar:2983:field_when:0:83
SUMMARY:Sigma-Prikry forcing, part 1
DTSTART:2020-05-06T08:00:00
DTEND:2020-05-06T10:00:00
DSCRIPTION:Speaker: Alejandro Poveda (Universitat de Barcelona)\n
Abstract:
In a joint project with A. Rinot and D. Sinapova we introduce a class of notions of forcing which we call $\Sigma$-Prikry, and show that many of the known Prikry-type notions of forcing that centers around singular cardinals of countable cofinality are $\Sigma$-Prikry. Among these examples one may find Prikry forcing and its supercompact version, Gitik-Sharon forcing or the Extender Based Prikry forcing due to Gitik and Magidor. Our first result shows that there is a functor $\mathbb{…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2974:field_when:0:84
SUMMARY:Transformations of the transfinite plane
DTSTART:2020-04-22T08:00:00
DTEND:2020-04-22T10:00:00
DSCRIPTION:Speaker: Jing Zhang (BIU)\n
Abstract:
We discuss the existence of certain transformation functions turning pairs of ordinals into triples (or pairs) of ordinals, that allows reductions of complicated Ramsey theoretic problems into simpler ones. We will focus on the existence of various kinds of strong colorings. The basic technique is Todorcevic's walks on ordinals. Joint work with Assaf Rinot.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2982:field_when:0:85
SUMMARY:Borel determinacy can not be proved in Zermelo Set Theoy
DTSTART:2020-04-01T08:00:00
DTEND:2020-04-01T10:00:00
DSCRIPTION:Speaker: Menachem Magidor (HUJI)\n
Abstract:
I'll speak about the Friedman-Martin theorem that Borel determinacy can not be proved in Zermelo Set Theoy. (Namely, one needs reflection for getting it).
Recoding is now available.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2981:field_when:0:86
SUMMARY:Strong colorings over partitions
DTSTART:2020-03-25T08:00:00
DTEND:2020-03-25T10:00:00
DSCRIPTION:Speaker: Menachem Kojman (BGU)\n
Abstract:
Let p:[\kappa]^2\to \theta be a partition of all unordered pairs from a cardinal \kappa to \theta pieces. A coloring f:[\kappa]^2\to \lambda is *strong over *p if for every A\subseteq \kappa with |A|=\kappa there is some i=i(A)<\theta such that ran (f\restriction ([A]^2\cap p^{-1}(\{i\}))=\lambda.
The partition symbol for asserting the existence of a strong \lambda-coloring on \kappa over a partition p is
\kappa\not\longrightarrow_p[\kappa]^2_\lambda.
In the talk we shall define…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2937:field_when:0:87
SUMMARY:Prof. Michael Golosovsky - 12.3.20
DTSTART:2020-03-12T12:00:00
DTEND:2020-03-12T13:00:00
DSCRIPTION:Speaker: Prof. Michael Golosovsky\n
Abstract:
TBA
Citations of scientific papers - a paradigmatic complex network
Dr. Michael Golosovsky
Racah Institute of Physics, Hebrew University of Jerusalem
The interdisciplinary field of complex networks has been actively developing since 1999. Many models of network growth have been proposed by theoretical physicists, mathematicians, and computer scientists but none of them was validated against the measurements according to accepted physical standards. We consider here one well-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2936:field_when:0:88
SUMMARY:Prof. Eran Bouchbinder - 5.3.20
DTSTART:2020-03-05T12:00:00
DTEND:2020-03-05T13:00:00
DSCRIPTION:Speaker: Prof. Eran Bouchbinder\n
Abstract:
Title: Soft excitations in glasses: Universality, localization and structural relaxation
Abstract:
Glasses are frustrated systems characterized by structural disorder, which endows them with unique properties compared to their crystalline counterparts. In this talk, we show that glassy disorder gives rise to low-frequency (soft) non-phononic excitations, which are quasi-localized in space and which follow a universal density of states proportional to
END:VEVENT
BEGIN:VEVENT
UID:calendar:2977:field_when:0:89
SUMMARY:On a paper of Peng and Wu, part 3
DTSTART:2020-02-27T10:00:00
DTEND:2020-02-27T12:00:00
DSCRIPTION:Speaker: Tanmay Inamdar (BIU) \n
Abstract:
I will discuss the paper of Peng and Wu `A Lindelof group with non-Lindelof Square'. I will focus on the oscillation results and the projection function. If time and patience permits, I will discuss some (unmotivated) slight strengthenings of their results in the partition calculus.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2972:field_when:0:90
SUMMARY:On a paper of Peng and Wu, part 2
DTSTART:2020-02-24T11:00:00
DTEND:2020-02-24T13:00:00
DSCRIPTION:Speaker: Tanmay Inamdar (BIU)\n
Abstract:
I will discuss the paper of Peng and Wu `A Lindelof group with non-Lindelof Square'. I will focus on the oscillation results and the projection function. If time and patience permits, I will discuss some (unmotivated) slight strengthenings of their results in the partition calculus.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2971:field_when:0:91
SUMMARY:The affine n-space is determined by its automorphism group
DTSTART:2020-02-19T13:00:00
DTEND:2020-02-19T14:00:00
DSCRIPTION:Speaker: Dr. Andriy Regeta (University of Jena)\n
Abstract:
Our base field is an uncountable algebraically closed field (of any characteristic). We show that an affine space is determined by the abstract group structure of its regular automorphism group in the category of connected affine varieties. To prove this we use tools from birational geometry and study commutative subgroups of the group of automorphisms of affine varieties.
(This is joint work with Serge Cantat and Junyi Xie).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2970:field_when:0:92
SUMMARY:On a paper of Peng and Wu, part 1
DTSTART:2020-02-17T11:00:00
DTEND:2020-02-17T13:00:00
DSCRIPTION:Speaker: Tanmay Inamdar (BIU)\n
Abstract:
I will discuss the paper of Peng and Wu `A Lindelof group with non-Lindelof Square'. I will focus on the oscillation results and the projection function. If time and patience permits, I will discuss some (unmotivated) slight strengthenings of their results in the partition calculus.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2966:field_when:0:93
SUMMARY:On Shelah 908; or, Strong chains of functions and sets
DTSTART:2020-02-10T11:00:00
DTEND:2020-02-10T13:00:00
DSCRIPTION:Speaker: Tanmay Inamdar (BIU)\n
Abstract:
I will discuss the paper of Shelah from the title and results which can be proved using similar techniques. A sample result is that one cannot have a chain of subsets of Omega2 strongly increasing modulo finite. The negative results we discuss can be contrasted with positive results of Koszmider on strong chains and results of Baumgartner on strongly almost disjoint families. The paper of Shelah is very short and relies only on a basic understanding of set theory (regular cardinals,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2935:field_when:0:94
SUMMARY:TBA - Prof. Agnieszka Wiszniewska-Matyszkie
DTSTART:2020-01-28T12:00:00
DTEND:2020-01-28T13:00:00
DSCRIPTION:Speaker: Prof. Agnieszka Wiszniewska-Matyszkie\n
Abstract:
Title: Dynamic optimization problems appearing while considering responsivity to consumers' expectations.
Anstract:
I'm going to present a dynamic optimization model for the optimal behaviour of a service provider
whose consumers have some prior expectations about service quality, which
adjust over time and they have discontinuous reaction to satisfying or dissatisfying experiences, which
influences the goodwill of the firm. We analyse the dynamic optimization
problem of the company…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2963:field_when:0:95
SUMMARY:Functional Inequalities on sub-Riemannian manifolds via QCD
DTSTART:2020-01-27T12:00:00
DTEND:2020-01-27T13:10:00
DSCRIPTION:Speaker: Prof. Emanuel Milman, Technion\n
Abstract:
We are interested in obtaining Poincar\’e and log-Sobolev inequalities on domains in sub-Riemannian manifolds
(equipped with their natural sub-Riemannian metric and volume measure).
It is well-known that strictly sub-Riemannian manifolds do not satisfy any type of Curvature-Dimension condition
CD(K,N), introduced by Lott-Sturm-Villani some 15 years ago, so we must follow a different path. We show that
while ideal (strictly) sub-Riemannian manifolds do not satisfy any type of CD…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2957:field_when:0:96
SUMMARY:Indestructibility of some compactness principles, part 2
DTSTART:2020-01-27T11:00:00
DTEND:2020-01-27T13:00:00
DSCRIPTION:Speaker: Šárka Stejskalová (Institute of Mathematics, Prague) \n
Abstract:
In the talk we will focus on compactness principles at the double successor of a regular cardinal kappa. We start by showing that if kappa^{<kappa} =kappa and lambda>kappa is a weakly compact cardinal, then in the Mitchell model V[M(kappa,lambda)] the tree property at kappa^{++} is indestructible under all kappa^+-cc forcing notions which live in the intermediate submodel V[Add(kappa,lambda)]. This result has direct applications for Prikry-style forcing notions and hence for the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2956:field_when:0:97
SUMMARY:On the realization space of the cube
DTSTART:2020-01-26T12:00:00
DTEND:2020-01-26T13:30:00
DSCRIPTION:Speaker: Daniel Kalmanovich (Hebrew University)\n
Abstract:
Given a d-dimensional polytope P, its realization space consists of all d-polytopes that have the same combinatorial type as P. For instance, consider the realization space of the d-simplex: since the d-simplex is projectively unique (i.e., any d-simplex can be transformed into any other d-simplex by a projective transformation) the realization space of the d-simplex is connected (and in fact, contractible). As a consequence, any two simplicial d-polytopes, after applying an…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2955:field_when:0:98
SUMMARY:How do algebras grow?
DTSTART:2020-01-22T09:00:00
DTEND:2020-01-22T10:00:00
DSCRIPTION:Speaker: Be'eri Greenfeld (Bar-Ilan University)\n
Abstract:
Gromov proved in 1981 that finitely generated groups of polynomial growth are virtually nilpotent. The Grigorchuk group and far reaching generalizations constructed upon it provide examples of groups with intermediate (namely, super-polynomial but subexponential) growth.
For finitely generated associative algebras, a much wider class of growth functions is possible. In particular, many functions, including intermediate growth functions and oscillating functions, are realizable as…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2998:field_when:0:99
SUMMARY:וישכם אברהם בבוקר - באיזו שעה?
DTSTART:2020-01-21T14:10:00
DTEND:2020-01-21T15:10:00
DSCRIPTION:Speaker: הרב דניאל גלוברמן\n
Abstract:
מאז תקופת אברהם אבינו ועד זמננו, נעמדה השמש במקומה באופן ניסי כמה פעמים כמבואר בתנ"ך וחז"ל, ויש לעיין באיזו מידה הניסים השפיעו על מקום השמש וזמני היום ההלכתיים. נדון בהרחבה על דיוק לוחות זמני הלכה בזמננו, שתלוי במזג אוויר ושיטות חישוב שונות, ונציג לפעם הראשונה מדידות וסטטיסטיקה בגורמים ההם ומידת השפעתם. המסקנה תהיה, השערת זמן עלות השחר ביום ובמקום השכמת אברהם אבינו לעקידת יצחק, עם הערכה עד איזה דיוק ניתן לחשב את זה.
להרצאה המצולמת
END:VEVENT
BEGIN:VEVENT
UID:calendar:2951:field_when:0:100
SUMMARY:Indestructibility of some compactness principles, part 1
DTSTART:2020-01-20T11:00:00
DTEND:2020-01-20T13:00:00
DSCRIPTION:Speaker: Šárka Stejskalová (Institute of Mathematics, Prague)\n
Abstract:
In the talk we will focus on compactness principles at the double successor of a regular cardinal kappa. We start by showing that if kappa^{<kappa} =kappa and lambda>kappa is a weakly compact cardinal, then in the Mitchell model V[M(kappa,lambda)] the tree property at kappa^{++} is indestructible under all kappa^+-cc forcing notions which live in the intermediate submodel V[Add(kappa,lambda)]. This result has direct applications for Prikry-style forcing notions and hence for the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2954:field_when:0:101
SUMMARY:The epsilon-t-net problem
DTSTART:2020-01-19T12:00:00
DTEND:2020-01-19T13:30:00
DSCRIPTION:Speaker: Chaya Keller (Ariel University)\n
Abstract:
In this talk we study a natural generalization of the classical epsilon-net problem (Haussler-Welzl 1987), which we call 'the epsilon-t-net problem': Given a hypergraph on n vertices and parameters t and epsilon, find a minimum-sized family S of t-element subsets of vertices such that each hyperedge of size at least epsilon n contains a set in . When t = 1, this corresponds to the epsilon-net problem.
We prove that any sufficiently large hypergraph with VC-dimension d admits an…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2953:field_when:0:102
SUMMARY:Lattice models of calculus and hydrodynamics
DTSTART:2020-01-19T10:00:00
DTEND:2020-01-19T11:00:00
DSCRIPTION:Speaker: Ruth Lawrence-Naimark, Hebrew University\n
Abstract:
As is well-known, discretisations often behave rather differently from the continuous models which they are meant to approximate, at the very least they may contain a much more delicate structure. We will discuss two manifestations of this. While trying to construct discrete analogues of the continuum picture of the differential graded algebra of differential forms on a manifold, we find that there is not just one, but rather there are three pictures, depending upon which one of the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2942:field_when:0:103
SUMMARY:Adding divisors on hyperelliptic curves via interpolation polynomials
DTSTART:2020-01-15T09:00:00
DTEND:2020-01-15T10:00:00
DSCRIPTION:Speaker: Prof. Yaacov Kopeliovich (University of Connecticut)\n
Abstract:
Let C be an algebraic curve of genus g. An effective procedure to reduce any non-special divisor on C to an equivalent divisor composed of g points is suggested. The hyperelliptic case is considered as the simplest model. The advantage of the proposed procedure is its explicitness: all steps are realized through arithmetic operations on polynomials. The resulting reduced divisor is obtained in the form of the Jacobi inversion problem, which unambiguously defines the divisor. At…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2952:field_when:0:104
SUMMARY:Constructing Souslin trees without diamond
DTSTART:2020-01-13T11:00:00
DTEND:2020-01-13T13:00:00
DSCRIPTION:Speaker: Ari Meir Brodsky (BIU)\n
Abstract:
We present an introduction to the subject of constructing Souslin trees and the challenges involved, focusing on our uniform construction of Souslin trees (at arbitrary uncountable regular cardinals) using the "microscopic approach". We will show that the constructions following this approach can be carried out even in the absence of diamond, providing a significant improvement at the level of a strongly inaccessible cardinal.
This is joint work with Assaf Rinot.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2950:field_when:0:105
SUMMARY:Word measures on the symmetric group
DTSTART:2020-01-12T12:00:00
DTEND:2020-01-12T13:30:00
DSCRIPTION:Speaker: Liam Hanany (Tel-Aviv University)\n
Abstract:
Given a word w in the free group on k generators, the word measure induced by w on the symmetric group S_n is the distribution obtained when substituting k independent uniform permutations into the word w. Puder and Parzanchevski (2015) estimated the expected number of fixed points of a permutation sampled according to this distribution.
We generalize this result to other statistics of the permutation, such as the expected number of cycles of a constant length, or the expected…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2934:field_when:0:106
SUMMARY:Interfacial dynamics of dissolving objects in fluid flow
DTSTART:2020-01-09T12:00:00
DTEND:2020-01-09T13:00:00
DSCRIPTION:Speaker: Prof. Chris Rycroft- Harvard\n
Abstract:
An advection–diffusion-limited dissolution model of an object being eroded by a two-dimensional potential flow will be presented. By taking advantage of conformal invariance of the model, a numerical method will be introduced that tracks the evolution of the object boundary in terms of a time-dependent Laurent series. Simulations of several dissolving objects will be shown, all of which show collapse to a single point in finite time. The simulations reveal a surprising connection…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2888:field_when:0:107
SUMMARY:Weyl groups and root systems in number fields
DTSTART:2020-01-08T09:00:00
DTEND:2020-01-08T10:00:00
DSCRIPTION:Speaker: Prof. Yuri Zarhin (Pennsylvania State University)\n
Abstract:
We classify the types of root systems R in the rings of integers O_K of number fields K such that the Weyl
group W(R) lies in the group generated by field automorphisms and multiplications by nonzero elements of K.
We also classify number fields K such that the lattice O_K provided with a trace-like form is isometric or similar to a root lattice.
This is a report on a joint work with Vladimir Popov (Steklov Institute, Moscow).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2948:field_when:0:108
SUMMARY:Solving Two-State Markov Games with Incomplete Information on One Side
DTSTART:2020-01-08T08:00:00
DTEND:2020-01-08T09:00:00
DSCRIPTION:Speaker: Galit Ashkenazi-Golan \n
Abstract:
We study the optimal use of information in Markov games with incomplete information on one side and two states.
We provide a finite-stage algorithm for calculating the limit value as the gap between stages goes to 0, and an optimal strategy for the informed player in the limiting game in continuous time.
This limiting strategy induces an epsilon-optimal strategy for the informed player, provided the gap between stages is small.
Our results demonstrate when the informed player should…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2949:field_when:0:109
SUMMARY:Bounding the Poisson bracket invariant on surfaces
DTSTART:2020-01-06T12:00:00
DTEND:2020-01-06T13:15:00
DSCRIPTION:Speaker: Prof. Lev Buhovsky, Tel-Aviv University\n
Abstract:
I will discuss the Poisson bracket invariant of a cover, which was introduced by L. Polterovich.
Initially, this invariant was studied via Floer theory, and lower bounds for it were established in
some situations. I will try to explain how one can obtain the conjectural lower bound in dimension 2, using only elementary arguments. This is a joint work with A. Logunov and S. Tanny, with a
contribution of F. Nazarov.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2944:field_when:0:110
SUMMARY:Compactness principles, GCH and anti-guessing principles
DTSTART:2020-01-06T11:00:00
DTEND:2020-01-06T13:00:00
DSCRIPTION:Speaker: Jing Zhang (BIU)\n
Abstract:
Compactness principles often times imply guessing principles, for example, if kappa is measurable, then the diamond principle holds at kappa.
Though small uncountable cardinals (like omega_2) is not a large cardinal, there are many compactness principles that can consistently hold at omega_2.
A theorem of Shelah states in the model where GCH holds and omega_2 is ``sufficiently’’ compact, then the diamond principle holds at the points in omega_2 having cofinality omega_1.
We will…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2943:field_when:0:111
SUMMARY:The polynomial method in computational geometry
DTSTART:2020-01-05T12:00:00
DTEND:2020-01-05T13:30:00
DSCRIPTION:Speaker: Esther Ezra (Bar-Ilan University)\n
Abstract:
Since the celebrated work of Guth and Katz on the Erdos distinct distances problem, polynomial partitioning became a central tool in solving incidence problems, as well as other main problems in discrete geometry. In spite of this progress, the application of polynomial partitioning in solving computational problems received considerably less attention. In particular, except for special settings (such as points in d-space), it is currently unknown how to efficiently construct…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2941:field_when:0:112
SUMMARY:On the asymptotic behavior of subsemigroups of free inverse semigroups
DTSTART:2020-01-05T10:00:00
DTEND:2020-01-05T11:00:00
DSCRIPTION:Speaker: Lev Shneerson, Hunter College, CUNY\n
Abstract:
We will speak about growth and Gelfand-Kirillov dimensions of subsemigroups of free inverse semigroups (joint work with Stuart Margolis).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2929:field_when:0:113
SUMMARY:On completion groups that are not complete and infinite towers of profinite groups
DTSTART:2020-01-01T09:00:00
DTEND:2020-01-01T10:00:00
DSCRIPTION:Speaker: Tamar Bar-On (Bar-Ilan University)\n
Abstract:
We investigate profinite completions of non-strongly complete profinite groups. We present and study the tower of profinite completions. Furthermore, we study how far a non-strongly complete profinite group can be from being strongly complete, i.e. how many non-open finite-index subgroups it admits.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2968:field_when:0:114
SUMMARY:לוח זמני היום בהלכה של ר' רפאל הלוי מהנובר
DTSTART:2019-12-31T15:00:00
DTEND:2020-02-13T16:00:00
DSCRIPTION:Speaker: ד"ר ערן רביב\n
Abstract:
רפאל הלוי מהנובר (1685-1779), עוזרו של המתמטיקאי הדגול לייבניץ, משמש כחולית החיבור בין האסטרונומיה התלמאית לאסטרונומיה המודרנית.
הבנתו המעמיקה והיכולות החישוביות המתקדמות שלו הקנו לו מקום של כבוד בחזית המלומדים היהודיים שהתמודדו עם קשיים בסוגיות אסטרונומיות בתלמודים וקשיים בהבנת הלכות קדוש החודש לרמב"ם.
רפאל הלוי תכנן להוציא לאור 4 ספרים אולם רק חלקם הופיע בדפוס (חלקים נוספים ספונים בכתבי יד שהוהדרו בשנים האחרונות ע"י אינג' איידלר מבלגיה, זמינים במרשתת בקישור -http://www.ajdler.com/…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2997:field_when:0:115
SUMMARY:קווי דמיון סמויים בין השפעת האסטרונומיה על הלוח העברי לבין קביעת תחילת הלוח המוסלמי.
DTSTART:2019-12-31T14:05:00
DTEND:2019-12-31T15:05:00
DSCRIPTION:Speaker: פרופ' אריאל כהן\n
Abstract:
במחלוקת בין רבי יהושע לבין רבי אליעזר קובע רבי יהושע כי העולם נברא בניסן.
לדעת המפרשים הביאור למחלוקת טמון בכך כי חודש ניסן הוא ראש השנה לתקופות. אנו נראה גם בהסתמך על מקורות נוספים כי בתחילת שנת התקופות חל גם המולד של חודש ניסן.
אנו נוכיח כי ראייה אסטרונומית זאת שביום בריאת העולם תחילת מזל טלה, השמש והלבנה היו בקו אחד ביחס ל"כדור הארץ", הייתה גם הבסיס לקביעת הלוח המוסלמי ראייה שהובילה לקביעה שהלוח המוסלמי מתחיל בתאריך ה 16 ביולי 622 למניין היוליאני.
להרצאה המצולמת
END:VEVENT
BEGIN:VEVENT
UID:calendar:2940:field_when:0:116
SUMMARY:Cocompact embeddings of function spaces
DTSTART:2019-12-30T12:00:00
DTEND:2019-12-30T13:45:00
DSCRIPTION:Speaker: Prof. Cyril Tintarev, Uppsala, visiting Technion\n
Abstract:
A sequence in a Banach space $E$ is called $G$-weak convergent, relative to a set $G$
of homeomorphisms of $E$ if $\forall g_k \in G$, $g_k(u_k-u)\rightharpoonup 0$. An
embedding of two Banach spaces is called $G$-cocompact if every $G$-weakly convergent
sequence in $E$ is convergent in $F$. Cocompact embeddings allow to improve convergence
of bounded sequences beyond weak convergence when there is no pertinent compactness.
On a series of examples in Sobolev, Besov, Lorenz-Zygmund…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2930:field_when:0:117
SUMMARY:A guessing principle from a Souslin tree, with an application to topology, part 3
DTSTART:2019-12-30T11:00:00
DTEND:2019-12-30T13:00:00
DSCRIPTION:Speaker: Roy Shalev (BIU)\n
Abstract:
Assuming the existence of a Souslin tree one can define a topology over the tree to get an Ostaszewski space. In this talk, we shall show how the existence of a Souslin tree gives rise to a topology on w1 which will form a "linear" Ostaszewski space.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2931:field_when:0:118
SUMMARY:Applied math seminar - Dr. Shay Deutsch
DTSTART:2019-12-26T12:00:00
DTEND:2019-12-26T13:00:00
DSCRIPTION:Speaker: Dr. Shay Deutsch\n
Abstract:
Title: Robust Methods for Topology Estimation in Unsupervised Learning
Abstract:
Learning graph connectivity has broad-ranging applications from 3D reconstruction to unsupervised learning. In this talk I will introduce a new method to learn the graph structure underlying noisy point set observations assumed to lie near a complex manifold. Rather than assuming regularity of the manifold itself, as customary, we assume regularity of the geodesic flow through the boundary of arbitrary …
END:VEVENT
BEGIN:VEVENT
UID:calendar:2932:field_when:0:119
SUMMARY:Matrix convexity, Choquet boundaries and Tsirelson problems
DTSTART:2019-12-23T12:00:00
DTEND:2019-12-23T14:00:00
DSCRIPTION:Speaker: Dr. Adam Dor On, University of Illinois, Urbana-Champaign, USA\n
Abstract:
Following work of Evert, Helton, Klep and McCullough on free LMI domains, we ask when a matrix
convex set is the closed convex hull of its Choquet points. This is a finite-dimensional version
of Arveson's non-commutative Krein-Milman theorem, and in fact some matrix convex sets can fail
to have any Choquet points. The general problem of determining whether a given matrix convex set
has this property turns out to be difficult because for certain matrix convex sets this is
equivalent to…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2900:field_when:0:120
SUMMARY:Some applications of the coloring number
DTSTART:2019-12-23T11:00:00
DTEND:2019-12-23T13:00:00
DSCRIPTION:Speaker: Peter Komjath (ELTE)\n
Abstract:
After an introduction to the basic facts on the coloring number, we give some applications to problems that do not seem to be connected to this notion.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2926:field_when:0:121
SUMMARY:Measure rigidity for Anosov flows via the factorization method
DTSTART:2019-12-22T10:00:00
DTEND:2019-12-22T11:00:00
DSCRIPTION:Speaker: Asaf Katz, University of Chicago\n
Abstract:
In the talk we will introduce those flows and their dynamical behavior.
Moreover, we show how the factorization method, pioneered by Eskin and Mirzakhani in their groundbreaking work about measure rigidity for the moduli space of translation surfaces, can be adapted to smooth ergodic theory and in particular towards the study of Anosov flows.
Using this adaption, we show that for a quantitatively non-integrable Anosov flow, every generalized u-Gibbs measure is absolutely…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2925:field_when:0:122
SUMMARY:Applied math seminar - Prof. Alfred M. Bruckstein
DTSTART:2019-12-19T12:00:00
DTEND:2019-12-19T13:00:00
DSCRIPTION:Speaker: Prof. Alfred M. Bruckstein\n
Abstract:
:Title
From Ants to A(ge)nts
The wonderfully Weird World of Multi-Agent Swarms
:Abstract
An ant colony is a marvel of cooperation and coordinated, purposeful
work carried out by simple a(ge)nts with very limited capabilities. Ants
do not have GPS systems, have no compasses nor odometers, do not
use laser range finders , nor do they have good memories or extraordinary
computational resources, and employ no sophisticated long-range sensing or
communication equipment. Yet they…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2911:field_when:0:123
SUMMARY:Pro-p identities of linear groups
DTSTART:2019-12-18T09:00:00
DTEND:2019-12-18T10:00:00
DSCRIPTION:Speaker: Dr. David El-Chai Ben-Ezra (University of California, San Diego)\n
Abstract:
It is a classical fact that free (discrete) groups can be embedded in GL_2(Z). In 1987, Zubkov showed that for a non-abelian free pro-p group F^(p), the situation changes, and for every p > 2, groups of the form GL_2(R) satisfy a "pro-p identity." More formally, for every p > 2 there exists a nontrivial element g of F^(p) that vanishes under every (continuous) homomorphism F^(p) --> GL_2(R), when R is a pro-finite commutative ring. In particular, when p > 2, F^(p)…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2928:field_when:0:124
SUMMARY:Multiple translational tiling in the plane
DTSTART:2019-12-16T13:05:00
DTEND:2019-12-16T14:00:00
DSCRIPTION:Speaker: Dr. Yang Qi, Peking University\n
Abstract:
In this talk, I will present some of my results in multiple translational tiling
in the Euclidean plane. For examples, besides parallelograms and centrally symmetric
hexagons, there is no other convex domain which can form any two-, three- or four-fold
translative tiling in the plane. However, there are two types of octagons and one type
of decagons which can form nontrivial five-fold translative tilings. Furthermore, a
convex domain can form a five-fold translative tiling of the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2927:field_when:0:125
SUMMARY:Optimal growth of frequently oscillating subharmonic functions
DTSTART:2019-12-16T12:00:00
DTEND:2019-12-16T13:00:00
DSCRIPTION:Speaker: Dr. Adi Glucksam, University of Toronto, Canada\n
Abstract:
In this talk I will present Nevanlinna-type tight bounds on the minimal possible
growth of subharmonic functions with a large zero set. We use a technique inspired
by a paper of Jones and Makarov.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2915:field_when:0:126
SUMMARY:Embedding C*-algebras into the Calkin algebra
DTSTART:2019-12-16T11:00:00
DTEND:2019-12-16T13:00:00
DSCRIPTION:Speaker: Andrea Vaccaro (BGU)\n
Abstract:
In this talk I will present an application of forcing techniques to C*-algebras, objects coming from functional analysis. A C*-algebra is a norm-closed, self-adjoint subalgebra of B(H), the algebra of all linear bounded operators on a complex Hilbert space H. The Calkin algebra Q(H), defined as the quotient of B(H) modulo the ideal of compact operators, is a C*-algebra which, for many good reasons, is considered the noncommutative analogue of the boolean algebra P(omega)/Fin. In this…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2923:field_when:0:127
SUMMARY:Fully commutative elements in affine Coxeter groups
DTSTART:2019-12-15T12:00:00
DTEND:2019-12-15T13:30:00
DSCRIPTION:Speaker: Riccardo Biagioli (Université Claude Bernard Lyon 1)\n
Abstract:
An element of a Coxeter group W is fully commutative if any two of its reduced decompositions are related by a series of transpositions of adjacent commuting generators. These elements were extensively studied by Stembridge, in the finite case. They index naturally a basis of the generalized Temperley–Lieb algebra of W.
In this talk, we give explicit descriptions of fully commutative elements when W is an affine Coxeter group. Using our characterizations we then enumerate these…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2918:field_when:0:128
SUMMARY:Fuglede's tiling-spectrality conjecture
DTSTART:2019-12-15T10:00:00
DTEND:2019-12-15T11:00:00
DSCRIPTION:Speaker: Nir Lev, Bar-Ilan University\n
Abstract:
Which domains in Euclidean space admit an orthogonal basis of exponential functions? For example, the cube is such a domain, but the ball is not. In 1974, Fuglede made a fascinating conjecture that these domains could be characterized geometrically as the domains which can tile the space by translations. I will survey the subject and report about the recent developments on Fuglede's conjecture.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2920:field_when:0:129
SUMMARY:Mathematical Modeling of Cyclic Population Dynamics
DTSTART:2019-12-12T12:00:00
DTEND:2019-12-12T13:00:00
DSCRIPTION:Speaker: Alexander Nepomnyashchy\n
Abstract:
:abstract
We consider deterministic models for three-species ecological systems
exhibiting cyclic (rock-paper-scissors) dynamics, which account for delay
or/and spatial nonlocality in interspecies competition. The biological
origin of the temporal and spatial nonlocalities is the secretion of a
toxin lethal to another species in the environment. The dynamics of
spatially homogeneous states is described by ODE models, which allow for
three classes of stable limit solution: (i)…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2890:field_when:0:130
SUMMARY:Limits of the Diagonal Cartan Subgroup in SL(n,R) and SL(n, Q_p)
DTSTART:2019-12-11T09:00:00
DTEND:2019-12-11T10:00:00
DSCRIPTION:Speaker: Dr. Arielle Leitner (Weizmann Institute of Science)\n
Abstract:
A conjugacy limit group is the limit of a sequence of conjugates of the positive diagonal Cartan
subgroup, C \leq SL(n) in the Chabauty topology. Over R, the group C is naturally associated to a projective n-1 simplex. We can compute the conjugacy limits of C by collapsing the n-1 simplex in different ways. In low dimensions, we enumerate all possible ways of doing this. In higher dimensions we show there are infinitely many non-conjugate limits of C.
In the Q_p case, SL(n,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2906:field_when:0:131
SUMMARY:Strong coding trees and applications to Ramsey theory on infinite graphs
DTSTART:2019-12-09T11:00:00
DTEND:2019-12-09T13:00:00
DSCRIPTION:Speaker: Natasha Dobrinen (Denver)\n
Abstract:
Abstract is attached
END:VEVENT
BEGIN:VEVENT
UID:calendar:2916:field_when:0:132
SUMMARY:On the local structure of oriented graphs -- a case study in flag algebras
DTSTART:2019-12-08T12:00:00
DTEND:2019-12-08T13:30:00
DSCRIPTION:Speaker: Dan Hefetz (Ariel University)\n
Abstract:
Let G be an n-vertex oriented graph. Let t(G) (respectively i(G)) be the probability that a random set of 3 vertices of G spans a transitive triangle (respectively an independent set). We prove that t(G) + i(G) is asymptotically at least 1/9. We also prove a stability result and an exact result. Namely, we describe an extremal construction, prove that it is essentially unique, and prove that if H is sufficiently far from that construction, then t(H) + i(H) is significantly larger than…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2914:field_when:0:133
SUMMARY:Delta-convergence and concentration compactness structures
DTSTART:2019-12-08T10:00:00
DTEND:2019-12-08T11:00:00
DSCRIPTION:Speaker: Cyril Tintarev (Uppsala, visiting Technion)\n
Abstract:
We present a structural theorem for bounded sequences in Banach spaces based on ideas of concentration compactness that is, on the role of non-compact invariance for isolating lack of convergence in a sum of localized "bubbles" . Surprisingly the argument requires not weak convergence but its less known cousin, Delta-convergence.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2913:field_when:0:134
SUMMARY:Quasicrystals as steady-state solutions to PDEs
DTSTART:2019-12-05T12:00:00
DTEND:2019-12-05T13:00:00
DSCRIPTION:Speaker: Ron Lifshitz, School of Physics & Astronomy, Tel aviv University\n
Abstract:
:Abstract
For many years, quasicrystals were observed only as solid-state metallic alloys, yet current research is actively exploring their formation
in a variety of soft materials, including systems of macromolecules, nanoparticles, and colloids. Much effort is being invested in
understanding the thermodynamic properties of these soft-matter quasicrystals in order to predict and possibly control the structures
that form, and hopefully to shed light on the broader, yet unresolved,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2893:field_when:0:135
SUMMARY:Alexandroff topology of algebras over an integral domain
DTSTART:2019-12-04T08:30:00
DTEND:2019-12-04T09:30:00
DSCRIPTION:Speaker: Dr. Shai Sarussi (Sami Shamoon College of Engineering)\n
Abstract:
Let S be an integral domain with field of fractions F, and let A be an F-algebra. An S-subalgebra R of A is called S-nice if R lies over S and the localization of R with respect to S\{0} is A. Let X be the set of all S-nice subalgebras of A. We define a notion of open sets on X which makes this set a T_0-Alexandroff space. This enables us to study the algebraic structure of X from a topological point of view. We prove that an irreducible subset of X has a supremum with respect to…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2919:field_when:0:136
SUMMARY:Multiplicity of eigenvalues of the circular clamped plate
DTSTART:2019-12-02T12:00:00
DTEND:2019-12-02T13:45:00
DSCRIPTION:Speaker: Prof. Dan Mangoubi, Hebrew University, Jerusalem\n
Abstract:
A celebrated theorem of C.L. Siegel from 1929 shows that the multiplicity of eigenvalues for the Laplace
eigenfunctions on the unit disk is at most two. More precisely, Siegel shows that positive zeros of Bessel
functions are transcendental. We study the fourth order clamped plate problem, showing that the multiplicity
of eigenvalues is uniformly bounded (by not more than six). Our method is based on new recursion formulas
and Siegel-Shidlovskii theory. The talk is…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2910:field_when:0:137
SUMMARY:Inaccessible Jónsson cardinals, part 3
DTSTART:2019-12-02T11:00:00
DTEND:2019-12-02T13:00:00
DSCRIPTION:Speaker: Shehzad Ahmed (BIU) \n
Abstract:
Our goal is to finish the proof that an inaccessible Jonson cardinal lambda must be lambda x omega Jonsson. We begin by reviewing some properties of the iterated trace operator, and discussing how it interacts with certain sets coming from Jonsson models. From there, we will recall some important results from the previous talks and prove the desired results.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2908:field_when:0:138
SUMMARY:Greedy maximal independent sets via local limits
DTSTART:2019-12-01T12:00:00
DTEND:2019-12-01T13:30:00
DSCRIPTION:Speaker: Peleg Michaeli (Tel-Aviv University)\n
Abstract:
The random greedy algorithm for finding a maximal independent set in a graph
has been studied extensively in various settings in combinatorics, probability,
computer science — and even in chemistry. The algorithm builds a maximal
independent set by inspecting the vertices of the graph one at a time according
to a random order, adding the current vertex to the independent set if it is
not connected to any previously added vertex by an edge.
In this talk I will present a natural and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2907:field_when:0:139
SUMMARY:A geometric inequality for length and volume in complex projective plane
DTSTART:2019-12-01T10:00:00
DTEND:2019-12-01T11:00:00
DSCRIPTION:Speaker: Mikhail Katz, Bar-Ilan University\n
Abstract:
In the 1950s, Carl Loewner proved an inequality relating the
shortest closed geodesics on a 2-torus to its area. Many
generalisations have been developed since, by Gromov and others. We
show that the shortest closed geodesic on an area-minimizing surface S
for a generic metric on CP^2 is controlled by the total volume, even
though the area of S is not. We exploit the Croke--Rotman inequality,
Gromov's systolic inequalities, the Kronheimer--Mrowka proof of the
Thom conjecture,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2901:field_when:0:140
SUMMARY:Isomorphic subgroups of finite solvable groups
DTSTART:2019-11-27T08:30:00
DTEND:2019-11-27T09:30:00
DSCRIPTION:Speaker: Prof. George Glauberman (University of Chicago)\n
Abstract:
In 2014, Moshe Newman asked the following question: If two subgroups of a finite solvable group are isomorphic and one is a maximal proper subgroup of G, must the other also be a maximal proper subgroup of G? This question is still open. I plan to discuss recent results with Geoffrey Robinson that give some sufficient conditions for an affirmative answer.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2912:field_when:0:141
SUMMARY:Spatial properties of congestion in street networks: a geometric version of Braess's paradox
DTSTART:2019-11-25T11:15:00
DTEND:2019-11-25T12:30:00
DSCRIPTION:Speaker: Prof. Gourab Ghoshal\n
Abstract:
Abstract: Streets networks are the primary facilitators of movement in urban systems, allowing residents to navigate the different functional components of a city. Since navigability is a key ingredient of socioeconomic activity, roads represent one of its most important infrastructural components and a large body of work has elucidated its structural properties. One such important metric, intricately related to the flow of people and goods and services, is the betweenness centrality…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2886:field_when:0:142
SUMMARY:Inaccessible Jónsson cardinals, part 2
DTSTART:2019-11-25T11:00:00
DTEND:2019-11-25T13:00:00
DSCRIPTION:Speaker: Shehzad Ahmed (BIU)\n
Abstract:
In the previous talk, we showed that if lambda is an inaccessible Jonsson cardinal, then lambda must be Mahlo. In this talk, we will start by reviewing some basic ideas from the previous talk, and start developing the machinery required to prove Shelah's full result: If lambda is an inaccessible Jonsson cardinal, then lambda must be lambda x omega Mahlo. Along the way, we will discuss Shelah's rank ideals as well as related club guessing results.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2905:field_when:0:143
SUMMARY:Word measures on groups
DTSTART:2019-11-24T12:00:00
DTEND:2019-11-24T13:30:00
DSCRIPTION:Speaker: Doron Puder (Tel-Aviv University)\n
Abstract:
Let G be a finite group. Every word w in the free group on, say, 2 generators x and y, induces a probability measure on G as follows: sample two uniformly random elements g and h from G and evaluate w(g,h) to get an element of G. For example, if w = xyxy^{-2}, one obtains the random element ghgh^{-2} in G. The study of word measures on groups has revealed a lot of beautiful structure with surprising connections to other fields of mathematics, and has shed light on the finite group G …
END:VEVENT
BEGIN:VEVENT
UID:calendar:2904:field_when:0:144
SUMMARY:High transitivity in algebra and geometry
DTSTART:2019-11-24T10:00:00
DTEND:2019-11-24T11:00:00
DSCRIPTION:Speaker: Mikhail Zaidenberg, Fourier Institute, Grenoble\n
Abstract:
An infinite group G is called highly transitive if it acts on some infiniteset m-transitively for any natural number m. We give a brief survey on some recent results on abstract highly transitive groups.
Then we pass to examples of affine algebraic varieties with the automorphism group acting highly transitively; specifically, of toric affine varieties. We show that a highly transitive group can be generated by a finite number of one-parameter subgroups; for the affine spaces, three…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2889:field_when:0:145
SUMMARY:Cyclic homology
DTSTART:2019-11-20T08:30:00
DTEND:2019-11-20T09:30:00
DSCRIPTION:Speaker: Prof. Jack Shapiro (Washington University in St. Louis)\n
Abstract:
For an algebra A over a unitary commutative ring k, we have the Hochschild homology HH_*(A). One use of it was a generalization of the modules of differential forms to non-commutative algebras. This gave us HDR_*(A), the non-commutative de Rham homology, developed by Alain Connes in his paper “Non-commutative differential geometry.” In that paper he also produced cyclic homology, HC_*(A), which is connected to both Hochschild and de Rham homology. The nicest connection between…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2903:field_when:0:146
SUMMARY:On single and paired shifted Funk transform
DTSTART:2019-11-18T12:00:00
DTEND:2019-11-18T13:35:00
DSCRIPTION:Speaker: Prof. M. Agranovsky, Bar-Ilan University\n
Abstract:
The classical result due to Funk is about the reconstruction of even functions on
the unit sphere in $R^n$ from their integrals over the cross-sections by the
hyperplanes (or k-planes) through the origin. In modern applications in tomography
and imaging, this transform is involved in reconstruction methods in diffusion MRI.
Last years, the shifted Funk transform, with the common point (center) of the cross-
sections different form the origin, has been studied by several authors.…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2885:field_when:0:147
SUMMARY:Inaccessible Jónsson cardinals, part 1
DTSTART:2019-11-18T11:00:00
DTEND:2019-11-18T13:00:00
DSCRIPTION:Speaker: Shehzad Ahmed (BIU) \n
Abstract:
In Sh413, Shelah showed that an inaccessible Jonsson cardinal \kappa must be \kappa x \omega Mahlo. In this series of talks, we will provide a new proof of this result. The first part will focus on showing that an inaccessible Jonsson cardinal must be Mahlo.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2898:field_when:0:148
SUMMARY:Collapsibility of simplicial complexes of graphs and hypergraphs
DTSTART:2019-11-17T12:00:00
DTEND:2019-11-17T13:30:00
DSCRIPTION:Speaker: Alan Lew (Technion)\n
Abstract:
Let X be a simplicial complex. Given a simplex σ ∈ X of dimension at most d − 1 that is contained in a unique maximal face of X, the operation of removing σ and all the simplices that contain it from X is called an elementary d-collapse. We say that X is d-collapsible if it can be reduced to the void complex by performing a sequence of elementary d-collapses. The collapsibility of X is the minimal d such that X is d-collapsible. The notion of d-collapsibility was introduced by Wegner…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2894:field_when:0:149
SUMMARY:Curves with boundary: Can you count them? Can you really?
DTSTART:2019-11-17T10:00:00
DTEND:2019-11-17T11:00:00
DSCRIPTION:Speaker: Sara Tukachinsky, IAS, Princeton\n
Abstract:
Open Gromov-Witten (OGW) invariants should count pseudoholomorphic maps from Riemann surfaces with boundary to a symplectic manifold, with boundary conditions and various constraints on boundary and interior marked points. The presence of boundary leads to bubbling phenomena that pose a fundamental obstacle to invariance. In a joint work with J. Solomon, we developed a general approach to defining genus zero OGW invariants.
The construction uses the heavy machinery of Fukaya A_\infty…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2882:field_when:0:150
SUMMARY:TBA
DTSTART:2019-11-14T12:00:00
DTEND:2019-11-14T13:30:00
DSCRIPTION:Speaker: פרופ' יורם לוזון\n
Abstract:
TBA
END:VEVENT
BEGIN:VEVENT
UID:calendar:2902:field_when:0:151
SUMMARY:סוגיה במסכת כתובות באספקלריה של תורת המשחקים
DTSTART:2019-11-14T09:50:00
DTEND:2019-11-14T10:50:00
DSCRIPTION:Speaker: פרופ' ישראל אומן\n
Abstract:
END:VEVENT
BEGIN:VEVENT
UID:calendar:2874:field_when:0:152
SUMMARY:Evaluation of non-commutative polynomials on a quaternion algebra
DTSTART:2019-11-13T08:30:00
DTEND:2019-11-13T09:30:00
DSCRIPTION:Speaker: Dr. Sergey Malev (Ariel University)\n
Abstract:
Let p be a multilinear polynomial in several non-commuting variables, with coefficients in an arbitrary field K. Kaplansky conjectured that for any n, the image of p evaluated on the set M_n(K) of nxn matrices is a vector space. We settle the analogous conjecture for a quaternion algebra.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2899:field_when:0:153
SUMMARY:Salem conditions in the non-periodic case
DTSTART:2019-11-11T12:00:00
DTEND:2019-11-11T13:30:00
DSCRIPTION:Speaker: Prof. E. Liflyand, Bar-Ilan University\n
Abstract:
In the classical sources, Salem's necessary conditions for a trigonometric series to be the Fourier
series of an integrable function are given in terms of ``some" sums. Realizing that, in fact, they
are given in terms of the discrete Hilbert transforms, we generalize these to the non-periodic case,
for functions from the Wiener algebra. Other relations of the two objects are also discussed.
The obtained necessary condition is used to construct a monotone function with non-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2884:field_when:0:154
SUMMARY:On the effect of adding kappa^+ many Cohen subsets to kappa
DTSTART:2019-11-11T11:00:00
DTEND:2019-11-11T13:00:00
DSCRIPTION:Speaker: Gabriel Fernandes (BIU)\n
Abstract:
This is joint work with Miguel Moreno and Assaf Rinot.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2897:field_when:0:155
SUMMARY:Property testing and expansion in cubical complexes
DTSTART:2019-11-10T12:00:00
DTEND:2019-11-10T13:30:00
DSCRIPTION:Speaker: Uzi Vishne (Bar-Ilan University)\n
Abstract:
We are given a 2-coloring of the edges of the complete graph. If the number of red edges in triangles is almost always even, then the coloring is approximately defined on vertices. Thus triangles "test" a function on edges to be defined from the vertices.
Replacing triangles by squares, and going up in the dimension, we show that differentials can test properties, as long as the cohomology group is sufficiently well understood.
Joint work with David Garber.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2887:field_when:0:156
SUMMARY:Doob equivalence and non-commutative peaking for Markov chains
DTSTART:2019-11-10T09:00:00
DTEND:2019-11-10T10:00:00
DSCRIPTION:Speaker: (Adam Dor-On (University of Copenhagen and UIU\n
Abstract:
The theory of Markov chains has applications in diverse areas of research such as group theory, dynamical systems, electrical networks and information theory. These days, connections with operator algebras seem to manifest mostly in quantum information theory, where Markov chains are generalized to quantum channels.
In this talk we will show how questions about operator algebras constructed from stochastic matrices, studied by Markiewicz and myself, still motivate new problems in…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2881:field_when:0:157
SUMMARY:Isoperimetry, Littlewood functions, and unitarisability of groups
DTSTART:2019-11-06T08:30:00
DTEND:2019-11-06T09:30:00
DSCRIPTION:Speaker: Dr. Maria Gerasimova (Bar-Ilan University)\n
Abstract:
See attached file.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2883:field_when:0:158
SUMMARY:Riesz bases of exponentials for convex polytopes
DTSTART:2019-11-04T12:00:00
DTEND:2019-11-04T13:20:00
DSCRIPTION:Speaker: Prof. Nir Lev, Bar-Ilan University \n
Abstract:
Which domains in Euclidean space admit a basis of exponential functions? The answer
depends on what we mean by a "basis". The best one can hope for is to have an orthogonal
basis of exponentials, but it is well-known that many reasonable domains do not have such
a basis. In this case, a Riesz basis is the next best thing one can hope for. I will
discuss a recent result joint with Alberto Debernardi, which deals with the construction
of Riesz bases of exponentials for convex…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2876:field_when:0:159
SUMMARY:PCF and the covering proof, part 2
DTSTART:2019-11-04T11:00:00
DTEND:2019-11-04T13:00:00
DSCRIPTION:Speaker: Dominik Adolf (BIU)\n
Abstract:
This is a continuation of the lecture from last week.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2896:field_when:0:160
SUMMARY:On Wilson's existence theorem and the monoid of continuous maps on block designs
DTSTART:2019-11-03T12:00:00
DTEND:2019-11-03T13:30:00
DSCRIPTION:Speaker: Stuart Margolis (Bar-Ilan University)\n
Abstract:
In 1974 Rick Wilson proved one of the most important theorems on combinatorial structures in the 20th century by showing that the easy necessary conditions on the parameters of a block design are eventually sufficient. The proof involves morphisms between block designs whose fibers allow for recursive constructions. The self-maps of a design form a monoid that are a fundamental part of the theory of designs. The algebraic properties of this monoid have not been explored up to now and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2875:field_when:0:161
SUMMARY:Stability and instability of spectrum for noisy perturbations of non-Hermitian matrices
DTSTART:2019-11-03T10:00:00
DTEND:2019-11-03T11:00:00
DSCRIPTION:Speaker: Ofer Zeituni, The Weizmann Institute\n
Abstract:
We discuss the spectrum of high dimensional non-Hermitian matrices under small noisy perturbations. That spectrum can be extremely unstable, as the maximal nilpotent matrix J_N with J_N(i,j)=1 iff j=i+1 demonstrates. Numerical analysts studied worst case perturbations, using the notion of pseudo-spectrum. Our focus is on finding the locus of most eigenvalues (limits of density of states), as well as studying stray eigenvalues ("outliers"). I will describe the background, show some…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2871:field_when:0:162
SUMMARY:PCF and the covering proof, part 1
DTSTART:2019-10-28T11:00:00
DTEND:2019-10-28T13:00:00
DSCRIPTION:Speaker: Dominik Adolf (BIU)\n
Abstract:
We will show how the argument from the proof of the covering lemma for the core model can be utilized to analyze the PCF structure of certain products. Which products can be analyzed depends on the severity of anti-large cardinal assumptions. The greatest generality seems to be achieved if the Mitchell order of cardinals in the core model is bounded below the singular cardinal in question.
This is joint work with Omer Ben-Neria.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2895:field_when:0:163
SUMMARY:Noncommutative Catalan numbers revisited
DTSTART:2019-10-27T12:00:00
DTEND:2019-10-27T13:30:00
DSCRIPTION:Speaker: Arkady Berenstein (University of Oregon)\n
Abstract:
The goal of my second talk on the subject (the first one was given at this seminar two years ago), which is also based on joint work with Vladimir Retakh, is twofold:
First, I will recall motivations, definition and basic properties of noncommutative Catalan numbers C_n, which belong to the free Laurent polynomial algebra in x_0,...,x_n. They admit interesting (commutative and noncommutative) specializations, one of them related to the Garsia-Haiman (q,t)-version Catalan numbers,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2872:field_when:0:164
SUMMARY:Predictive sets
DTSTART:2019-10-27T10:00:00
DTEND:2019-10-27T11:00:00
DSCRIPTION:Speaker: Benjamin Weiss, The Hebrew University\n
Abstract:
A subset of the integers P is called predictive if for any zero entropy finite-valued stationary process {X_i} , X_0 is measurable with respect to the sigma-algebra generated by the {X_i ; i \in P}. Zero entropy processes are exactly those for which N itself is a predictive set. I will discuss come necessary and some sufficient conditions for a set to be predictive. It turns out that this notion is related to the classical Riesz sets in harmonic analysis that were defined many…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2867:field_when:0:165
SUMMARY:Blocks of defect 1 and units in integral group rings
DTSTART:2019-09-26T08:00:00
DTEND:2019-09-26T09:00:00
DSCRIPTION:Speaker: Dr. Leo Margolis (Vrije Universiteit Brussel)\n
Abstract:
Over the decades that U(ZG), the unit group of the integral group ring of a finite group G, has been studied, many conjectures have been raised on how the structure of G influences the structure of subgroups of U(ZG). Though it often took considerable time, counterexamples for the strongest of these conjectures were found in the class of solvable groups. Contrary to this, the arithmetic properties of finite subgroups of U(ZG) are very restricted for solvable G. For instance, the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2849:field_when:0:166
SUMMARY:Rainbow Ramsey theory at uncountable cardinals, part 2
DTSTART:2019-09-16T10:00:00
DTEND:2019-09-16T12:00:00
DSCRIPTION:Speaker: Jing Zhang (BIU) \n
Abstract:
this is a continuation of our previous talk
END:VEVENT
BEGIN:VEVENT
UID:calendar:2847:field_when:0:167
SUMMARY:Rainbow Ramsey theory at uncountable cardinals, part 1
DTSTART:2019-09-09T10:00:00
DTEND:2019-09-09T12:00:00
DSCRIPTION:Speaker: Jing Zhang (BIU)\n
Abstract:
A typical problem studied in Rainbow Ramsey theory is: given a coloring of pairs of ordinals such that each color is used “not too many times”, is it possible to find a subset that is “rainbow”, namely the coloring restricted to the pairs of this subset is injective. Different problems arise by varying the parameters, for example, the “type” of the source cardinal (successor of regular/regular, limit singular/regular) or the exact meaning of “not too many times”. In this talk, we will…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2846:field_when:0:168
SUMMARY:A guessing principle from a Souslin tree, with an application to topology, part 2
DTSTART:2019-09-09T07:00:00
DTEND:2019-09-09T09:00:00
DSCRIPTION:Speaker: Roy Shalev (BIU)\n
Abstract:
Last week, we formulated a weakening of Ostaszewski's club principle, and showed that it holds assuming the existence of a Souslin tree. In this talk, we shall show that our principle suffices for the construction of an Ostaszewski space.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2845:field_when:0:169
SUMMARY:A guessing principle from a Souslin tree, with an application to topology, part 1
DTSTART:2019-09-02T10:00:00
DTEND:2019-09-02T12:00:00
DSCRIPTION:Speaker: Roy Shalev (BIU)\n
Abstract:
We formulate a weakening of Ostaszewski's club principle, and show that it holds assuming the existence of a Souslin tree. In the next talk, we shall show that our principle suffices for the construction of an Ostaszewski space.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2834:field_when:0:170
SUMMARY:Tree property at the first and double successors with arbitrary gaps, part 4
DTSTART:2019-06-24T10:00:00
DTEND:2019-06-24T12:00:00
DSCRIPTION:Speaker: Alejandro Poveda (Universitat de Barcelona) \n
Abstract:
In this talk we shall present a proof of the consistency, modulo suitable large cardinals assumptions, of the following theory:
"There is a strong limit cardinal \kappa with cof(\kappa)>\aleph_0 such that TP(\kappa^+) and TP(\kappa^{++}) hold and 2^\kappa is arbitrarily large"
Here by arbitrarily large we mean that 2^\kappa can be any cardinal \gamma\geq \kappa^{++} with cof(\gamma)>\kappa.The proof relies on ideas of Sinapova, Unger and Friedman-Honzik-Stejskalová and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2814:field_when:0:171
SUMMARY:On the set of specializations of a Galois cover
DTSTART:2019-06-19T07:30:00
DTEND:2019-06-19T08:30:00
DSCRIPTION:Speaker: Dr. Joachim Koenig (KAIST -- Korea Advanced Institute of Science and Technology)\n
Abstract:
One of the most successful approaches to the inverse Galois problem over Q is via specialization of polynomials f(t,X) in two (or more) variables, or equivalently, specialization of Galois covers of the projective line. The fundamental underlying result, Hilbert's irreducibility theorem, ensures that this specialization process preserves the Galois group "most of the time".
In this talk, I will review a series of recent results under the following general question: Which kinds of "…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2833:field_when:0:172
SUMMARY:Generating functionals on quantum groups
DTSTART:2019-06-17T11:00:00
DTEND:2019-06-17T12:40:00
DSCRIPTION:Speaker: Dr. Ami Viselter, University of Haifa\n
Abstract:
We will discuss generating functionals on locally compact
quantum groups. One type of examples comes from probability: the family
of distributions of a L\'evy process form a convolution semigroup,
which in turn admits a natural generating functional. Another type
of examples comes from (locally compact) group theory, involving semigroups
of positive-definite functions and conditionally negative-definite
functions, which provide important information about the group's geometry.
We will…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2831:field_when:0:173
SUMMARY:Tree property at the first and double successors with arbitrary gaps, part 3
DTSTART:2019-06-17T10:00:00
DTEND:2019-06-17T12:00:00
DSCRIPTION:Speaker: Alejandro Poveda (Universitat de Barcelona) \n
Abstract:
In this talk we shall present a proof of the consistency, modulo suitable large cardinals assumptions, of the following theory:
"There is a strong limit cardinal \kappa with cof(\kappa)>\aleph_0 such that TP(\kappa^+) and TP(\kappa^{++}) hold and 2^\kappa is arbitrarily large"
Here by arbitrarily large we mean that 2^\kappa can be any cardinal \gamma\geq \kappa^{++} with cof(\gamma)>\kappa.The proof relies on ideas of Sinapova, Unger and Friedman-Honzik-Stejskalová and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2829:field_when:0:174
SUMMARY:L-functions, periods and quantization of representations
DTSTART:2019-06-16T09:00:00
DTEND:2019-06-16T10:00:00
DSCRIPTION:Speaker: Andre Reznikov, Bar-Ilan University\n
Abstract:
I will discuss new (analytic) developments in the old paradigm in automorphic functions connecting L-functions to representation theory via the fundamental notion of a period. I revisit the orbit method of Kirillov with the aim of making it "effective".
END:VEVENT
BEGIN:VEVENT
UID:calendar:2830:field_when:0:175
SUMMARY:Root-Reductive Lie Algebras
DTSTART:2019-06-11T11:15:00
DTEND:2019-06-11T12:30:00
DSCRIPTION:Speaker: Thanasin Nampaisarn, WIS\n
Abstract:
Root-reductive Lie algebras are relatively well behaved, countable-dimensional Lie algebras. In this talk, we shall discuss the definition of these Lie algebras as well as their important subalgebras---Borel subalgebras, Cartan subalgebras, and splitting maximal toral subalgebras. We shall also dwell on some representations of these Lie algebras if time permits.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2828:field_when:0:176
SUMMARY:Some problems of tropical optimization
DTSTART:2019-06-06T10:05:00
DTEND:2019-06-06T11:05:00
DSCRIPTION:Speaker: Sergey Sergeev, University of Birmingham\n
Abstract:
Tropical mathematics is an area of mathematics developed over the tropical semi-ring, where the usual arithmetic operations are replaced with max (playing the role of addition) and plus (playing the role of multiplication). In this talk we will consider some optimization problems that can be formulated and solved in the framework of tropical mathematics, such as: tropical analogue of linear-fractional programming, tropical pseudo-quadratic programming and tropical analogues of bi-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2815:field_when:0:177
SUMMARY:Group gradings on finite-dimensional division algebras
DTSTART:2019-06-05T08:00:00
DTEND:2019-06-05T09:00:00
DSCRIPTION:Speaker: Prof. Darrell Haile (Indiana University)\n
Abstract:
Let A be an algebra over a field k, and let G be a finite group. We say A is G-graded if there are k-subspaces A_g for all g in G such that A is the direct sum of the subspaces A_g, and A_g A_h is contained in A_gh for all elements g,h of G. Finite group gradings play an important role in the study of finite-dimensional division algebras and, more generally, in the study of finite-dimensional central simple algebras. For example, crossed product algebras, which provide the bridge…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2820:field_when:0:178
SUMMARY:Voronoi cells of varieties
DTSTART:2019-06-05T07:00:00
DTEND:2019-06-05T08:00:00
DSCRIPTION:Speaker: Madeleine Weinstein (University of California, Berkeley)\n
Abstract:
Every real algebraic variety determines a Voronoi decomposition of its ambient Euclidean space. Each Voronoi cell is a convex semialgebraic set in the normal space of the variety at a point. We compute the algebraic boundaries of these Voronoi cells. Using intersection theory, we give a formula for the degrees of the algebraic boundaries of Voronoi cells of curves and surfaces. We discuss an application to low-rank matrix approximation. This is joint work with Diego Cifuentes,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2842:field_when:0:179
SUMMARY:הלוח העברי: סינכרוניזציה - בין חשבון לחווייה
DTSTART:2019-06-04T14:00:00
DTEND:2019-06-04T15:00:00
DSCRIPTION:Speaker: הרב שבתי הכהן רפופורט\n
Abstract:
הרמב"ם וסיעתו סוברים שבנוסף לחשבון הקובע את קידוש החודש יש צורך בעדים ובקידוש בית דין. את העדים בודקים על פי החשבון, וכללי החשבון פוזיטיבסטיים במהותם. מדוע יש צורך בעדים ובבית דין, הלא מספיק מתמטיקאי טוב שיקבע את החודש. יתר על כן, הרמב"ם בספר המצוות, ובהלכות קידוש החודש, כותב שגם בזמננו אנחנו צריכים את בני ארץ ישראל לקידוש החודש, ואין אנו סומכים על חשבון הנעשה בחוץ לארץ. איזו משמעות יכולה להיות בזהותו של עושה החשבון בחשבון שכלליו פשוטים עד כדי ש"אפילו תינוקות של בית רבן מגיעין עד סופו…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2827:field_when:0:180
SUMMARY:Weighted norm inequalities for integral transforms with splitting kernels
DTSTART:2019-06-03T11:00:00
DTEND:2019-06-03T12:40:00
DSCRIPTION:Speaker: Dr. Alberto Debernardi, Bar-Ilan University\n
Abstract:
Given an integral transform on the positive real line, we say that its kernel is
splitting if it satisfies upper pointwise estimates given by products of two
functions, each of them taken in a different variable. We discuss necessary and/or
sufficient conditions weighted norm inequalities involving these transforms to
hold. Sharpness of the results is directly related to the sharpness of the upper
estimates for the kernels that we find.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2826:field_when:0:181
SUMMARY:Tree property at the first and double successors with arbitrary gaps, part 2
DTSTART:2019-06-03T10:00:00
DTEND:2019-06-03T12:00:00
DSCRIPTION:Speaker: Alejandro Poveda (Universitat de Barcelona)\n
Abstract:
In this talk we shall present a proof of the consistency, modulo suitable large cardinals assumptions, of the following theory:
"There is a strong limit cardinal \kappa with cof(\kappa)>\aleph_0 such that TP(\kappa^+) and TP(\kappa^{++}) hold and 2^\kappa is arbitrarily large"
Here by arbitrarily large we mean that 2^\kappa can be any cardinal \gamma\geq \kappa^{++} with cof(\gamma)>\kappa.The proof relies on ideas of Sinapova, Unger and Friedman-Honzik-Stejskalová and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2824:field_when:0:182
SUMMARY:Prediction of random and chaotic dynamics in nonlinear optics
DTSTART:2019-05-30T10:00:00
DTEND:2019-05-30T11:30:00
DSCRIPTION:Speaker: Amir Sagiv, TAU\n
Abstract:
The prediction of interactions between multiple high-power laser beams is a longstanding open problem in physics. One traditional assumption in this area is that these interactions are deterministic. We show, however, that a single beam may lose its initial phase information in the presence of input noise. This "loss of phase", obtained in the classical description of nonlinear laser propagation, the Nonlinear Schrodinger equation (NLS), renders the multiple-beams interactions…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2807:field_when:0:183
SUMMARY:Tree property at the first and double successors with arbitrary gaps, part 1
DTSTART:2019-05-27T10:00:00
DTEND:2019-05-27T12:00:00
DSCRIPTION:Speaker: Alejandro Poveda (Universitat de Barcelona)\n
Abstract:
In this talk we shall present a proof of the consistency, modulo suitable large cardinals assumptions, of the following theory:
"There is a strong limit cardinal \kappa with cof(\kappa)>\aleph_0 such that TP(\kappa^+) and TP(\kappa^{++}) hold and 2^\kappa is arbitrarily large"
Here by arbitrarily large we mean that 2^\kappa can be any cardinal \gamma\geq \kappa^{++} with cof(\gamma)>\kappa.The proof relies on ideas of Sinapova, Unger and Friedman-Honzik-Stejskalová and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2823:field_when:0:184
SUMMARY:What is "quantum determinant"?
DTSTART:2019-05-26T09:00:00
DTEND:2019-05-26T10:00:00
DSCRIPTION:Speaker: Dimitri Gourevitch, University of Valenciennes, France\n
Abstract:
Quantum determinant is an analog of the usual determinant
which lives in a Quantum Matrix Algebra (QMA). I plan
to introduce the notion of QMAs and quantum analogs
of some symmetric polynomials in these algebras.
In particular, such "quantum symmetric elements"
in Generalized Yangians will be exhibited. Also, I plan
to discuss the role of these objects in Integrable
Systems theory.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2812:field_when:0:185
SUMMARY:Tamagawa numbers of linear algebraic groups over function fields
DTSTART:2019-05-22T07:30:00
DTEND:2019-05-22T08:30:00
DSCRIPTION:Speaker: Dr. Zev Rosengarten (Hebrew University of Jerusalem)\n
Abstract:
In 1981, Sansuc obtained a formula for Tamagawa numbers of reductive groups over number fields, modulo some then unknown results on the arithmetic of simply connected groups which have since been proven, particularly Weil's conjecture on Tamagawa numbers over number fields. One easily deduces that this same formula holds for all linear algebraic groups (not just reductive) over number fields. Sansuc's method still works to treat reductive groups in the function field setting, thanks…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2819:field_when:0:186
SUMMARY:An informal discussion on the periplectic Lie superalgebra
DTSTART:2019-05-21T11:00:00
DTEND:2019-05-21T12:30:00
DSCRIPTION:Speaker: Shifra Reif, BIU\n
Abstract:
I will discuss some ideas from a recent breakthrough in the field of Lie superalgebras:
https://arxiv.org/abs/1610.08470
No prior knowledge on Lie superalgebras will be assumed.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2818:field_when:0:187
SUMMARY:SHANNON SAMPLING ON MANIFOLDS AND GRAPHS
DTSTART:2019-05-20T11:00:00
DTEND:2019-05-20T12:40:00
DSCRIPTION:Speaker: Prof. Isaac Pesenson, Temple University, Philadelphia, USA\n
Abstract:
One of the most interesting properties of the so called bandlimited functions
(=Palley-Wiener functions), i. e. functions whose Fourier transform has compact
support, is that they are uniquely determined by their values on some countable sets
of points and can be reconstructed from such values in a stable way. The sampling
problem for band limited functions had attracted attention of many mathematicians.
The mathematical theory of reconstruction of band limited functions from discrete…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2809:field_when:0:188
SUMMARY:A combinatorial argument of p=t, part 2
DTSTART:2019-05-20T10:00:00
DTEND:2019-05-20T12:00:00
DSCRIPTION:Speaker: Jialiang He (BIU) \n
Abstract:
We will finish the proof from the last meeting.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2810:field_when:0:189
SUMMARY:Logical properties of random graphs
DTSTART:2019-05-19T09:00:00
DTEND:2019-05-19T10:00:00
DSCRIPTION:Speaker: Simcha Haber, Bar-Ilan University\n
Abstract:
A graph property is first order expressible if it can be written as a formal sentence using the universal and existential quantifiers with variables ranging over the vertices of the graph, the usual connectives and the relations = and ~, where x~y stands for adjacency.
First order expressible properties have been studied using random finite models. That is, by looking on the possible behavior of first order properties given a probability space of graphs, e.g., G(n,p). A number of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2811:field_when:0:190
SUMMARY:Moduli space of matroids
DTSTART:2019-05-15T07:30:00
DTEND:2019-05-15T08:30:00
DSCRIPTION:Speaker: Prof. Oliver Lorscheid (IMPA)\n
Abstract:
This is an overview talk about my paper with Matt Baker with the same title. I will introduce matroids with coefficients, give a rough idea of how ordered blueprints enter the picture and how the moduli space of matroids is constructed, and then
finally turn to an outline of a new proof of Tutte's theorem that a matroid is regular if and only if it is binary and orientable.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2808:field_when:0:191
SUMMARY:On some aspects of the coupon collector's problem
DTSTART:2019-05-12T09:00:00
DTEND:2019-05-12T10:00:00
DSCRIPTION:Speaker: Daniel Berend, Ben-Gurion University\n
Abstract:
Suppose that a company distributes a commercial product and that each package contains a coupon. There are $n$ types of coupons, and a customer wants to collect at least one of each. How many packages need to be bought on the average until getting all coupons? This is referred to as the coupon collector problem, and goes back at least as far as de Moivre.
Clearly, one expects that, in the beginning of the process, most coupons obtained will be new ones. As we continue, it takes more…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2806:field_when:0:192
SUMMARY:Topologically semisimple topological rings
DTSTART:2019-05-07T11:10:00
DTEND:2019-05-07T13:00:00
DSCRIPTION:Speaker: Leonid Positselski\n
Abstract:
The classical Wedderburn-Artin theorem describes associative rings A for which the category of A-modules is semisimple. This turns out to be a left-right symmetric property: the category of left A-modules is semisimple if and only if the category of right A-modules is. In this talk, I will present a generalization of the Wedderburn-Artin theory to topololgical associative rings R in which open right ideals form a base of neighborhoods of zero. The talk will start with a discussion of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2802:field_when:0:193
SUMMARY:Diamond^{sharp} from LCC, and applications to GDST
DTSTART:2019-05-06T10:00:00
DTEND:2019-05-06T12:00:00
DSCRIPTION:Speaker: Gabriel Fernandes (BIU)\n
Abstract:
Local club condensation (LCC) is an abstract formulation of a condensation property that canonical L-like models have. It was introduced by Friedman and Holy. Diamond^{sharp} is a strengthening of Jensen's diamond principle which was introduced by Devlin.
We shall show that diamond^{sharp} follows from LCC and the existence of a suitable Delta_1 definable well order, and then present an application of diamond^{sharp} to Generalized Descriptive Set Theory (GDST).
This is joint work…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2803:field_when:0:194
SUMMARY:Dynamically defined function graphs
DTSTART:2019-05-05T09:00:00
DTEND:2019-05-05T10:00:00
DSCRIPTION:Speaker: Karoly Simon, Technical University of Budapest\n
Abstract:
This talk is an overview on the dimension theory of some dynamically defined function graphs, like Takagi and Weierstrass function. In particular, we study the dimension of Markovian fractal interpolation functions (which play important role in various applications) and generalized Takagi functions generated by non-Markovian dynamics.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2799:field_when:0:195
SUMMARY:Single-Cell RNA sequencing - statistical challenges and its application to uncovering cancer heterogeneity
DTSTART:2019-05-02T10:00:00
DTEND:2019-05-02T11:30:00
DSCRIPTION:Speaker: Idan Alter from the Weizmann institute\n
Abstract:
Single-Cell RNA sequencing (scRNA-seq) is an emerging technology with the promise to uncover the transcriptome at the ultimate resolution of single cells. However, in order to make sense of the data, one must overcome the technical and biological noise inherent in the process. In this introductory talk which assumes no biological background, I will present the the concept of RNA sequencing and its ability to identify different cell types, the obfuscating factors encountered in such…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2801:field_when:0:196
SUMMARY:Local-global principles via combinatorial topology and rationality
DTSTART:2019-05-01T07:30:00
DTEND:2019-05-01T08:30:00
DSCRIPTION:Speaker: Prof. Daniel Krashen (Rutgers University)\n
Abstract:
Understanding algebraic structures such as Galois extensions, quadratic forms, division algebras and torsors for linear algebraic groups, can give important insights into the arithmetic of fields. In this talk, I will discuss recent work and work in progress showing ways in which parts of the arithmetic of function fields over complete fields may be encoded in the combinatorial topology of the special fiber. I will then describe how these observations lead to algebraic versions of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2800:field_when:0:197
SUMMARY:L-functions and Functoriality
DTSTART:2019-04-30T11:00:00
DTEND:2019-04-30T13:00:00
DSCRIPTION:Speaker: Avner Segal, Bar-Ilan University\n
Abstract:
In my previous talk, I described the partial L-functions of cuspidal automorphic representations and said that their conjectured meromorphic continuation is important for the theory of automorphic forms. I then talked about integral representations as a method for proving this meromorphic continuation.
In this talk (which will be mostly independent of the previous one), I will describe a softened version of functoriality (which is the main theme in the Langlands program) and how L-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2805:field_when:0:198
SUMMARY:On some inverse and nonlocal problems for operator differential equations and numerical methods for their solution
DTSTART:2019-04-29T11:00:00
DTEND:2019-04-29T12:20:00
DSCRIPTION:Speaker: Prof. Yuli Eidelman, Tel-Aviv University\n
Abstract:
We study some nonlocal problems for operator differential equations of the form
$$\frac{dv}{dt} = Av + f(t)$$
with an unbounded operator A in vector spaces. For a wide classes of equations we obtain necessary
and sufficient conditions of the unique solvability and the formulas for solutions of such problems.
In the second part of the talk we present fast numerical algorithms for solution of these problems
for matrix equations with rank structured matrices.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2798:field_when:0:199
SUMMARY:Large cardinals, substructures, and Chang's Conjecture
DTSTART:2019-04-28T09:00:00
DTEND:2019-04-28T10:00:00
DSCRIPTION:Speaker: Yair Hayut, Kurt Goedel Research Center, Vienna\n
Abstract:
One of the basic results in model theory is Lowenheim-Skolem. It states that every infinite model has infinite sub-models of any size. Elementary substructures basically catch all intrinsic properties of the large structure (first order properties). Obtaining substructure with more similarity to the original structure (second order properties) is more subtle, and often independent of the standard axioms of set theory.
In this talk I will discuss a special case of a second-order…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2776:field_when:0:200
SUMMARY:Brackets and superalgebras
DTSTART:2019-04-10T07:30:00
DTEND:2019-04-10T08:30:00
DSCRIPTION:Speaker: Prof. Efim Zelmanov (University of California, San Diego)\n
Abstract:
We will discuss important examples of infinite dimensional Lie superalgebras and their representations.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2795:field_when:0:201
SUMMARY:A general coefficient theorem for univalent functions
DTSTART:2019-04-08T11:00:00
DTEND:2019-04-08T12:20:00
DSCRIPTION:Speaker: Prof. Samuel Krushkal, Bar-Ilan University\n
Abstract:
The estimating holomorphic functionals on the classes of univalent functions depending on the
Taylor coefficients $a_n$ of these functions is important in various geometric and physical
applications of complex analysis, because these coefficients reflect the fundamental intrinsic
features of conformal maps.
The goal of the talk is to outline the proof of a new general theorem on maximization of homogeneous
polynomial (in fact, more general holomorphic) coefficient functionals
$$J(f…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2792:field_when:0:202
SUMMARY:A combinatorial argument of p=t, part 1
DTSTART:2019-04-08T10:00:00
DTEND:2019-04-08T12:00:00
DSCRIPTION:Speaker: Jialiang He (BIU) \n
Abstract:
The Minimal Tower Problem was one of most famous question in Cardinal Invariants. We will present a combinatorial argument of this proof, which without using model theory and forcing, motivated by Malliaris and Shelah's proof.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2791:field_when:0:203
SUMMARY:Products of uncountable structures
DTSTART:2019-04-07T09:00:00
DTEND:2019-04-07T10:00:00
DSCRIPTION:Speaker: Assaf Rinot, Bar-Ilan University\n
Abstract:
It is well-known that the product of two compact topological
spaces is again compact, but that the product of two Lindelof spaces
need not be Lindelof. In this talk, we shall address questions of these
flavor, focusing on a joint project of the speaker together with Chris
Lambie-Hanson.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2790:field_when:0:204
SUMMARY:Modeling flocks of birds and plagues of locusts
DTSTART:2019-04-04T10:00:00
DTEND:2019-04-04T11:30:00
DSCRIPTION:Speaker: Leah Edelstein-Keshet, University of British Columbia \n
Abstract:
Groups of animals display fascinating patterns of collective behavior. But how does group behavior emerge from the underlying actions of individuals and their interactions with one another? I will describe mathematical modeling research in my group that addresses such questions.
What social forces makes for a cohesive flock of birds? Can we infer such rules from observing flocks in nature? I will describe a project carried out in downtown Vancouver (BC, Canada) were flocks of aquatic…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2788:field_when:0:205
SUMMARY:Powering of high-dimensional expanders
DTSTART:2019-04-03T07:30:00
DTEND:2019-04-03T08:30:00
DSCRIPTION:Speaker: Dr. Ori Parzanchevski (Hebrew University of Jerusalem)\n
Abstract:
Powering the adjacency matrix of an expander graph results in a better expander of higher degree. High dimensional expanders are simplicial complexes which generalize the notion of expanders. In these settings, we look for an analogue of the powering operation. We show that the naive approach to powering does not yield high dimensional expanders in general, but that for quotients of Bruhat Tits buildings a powering operation arises from so-called "geodesic walks". The analysis of the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2793:field_when:0:206
SUMMARY:The doubling construction for integral representations of L-functions
DTSTART:2019-04-02T11:00:00
DTEND:2019-04-02T12:30:00
DSCRIPTION:Speaker: Amiya Kumar Mondal \n
Abstract:
In this talk, we will present an overview of the doubling construction for integral representations of L-functions. An explicit construction will be presented for quasi-split special orthogonal groups.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2781:field_when:0:207
SUMMARY:All about mad families
DTSTART:2019-04-01T10:00:00
DTEND:2019-04-01T12:00:00
DSCRIPTION:Speaker: Asger Törnquist (Københavns Universitet)\n
Abstract:
I will give an overview of the developments in the past 5 years regarding mad families.
We'll study families of subsets of the natural numbers, and say that such a family is almost disjoint if any two distinct elements intersect finitely. The Axiom of Choice implies the existence of infinite almost disjoint family which is maximal under inclusion.
Mathias proved in the late 1960s that it is consistent with ZF+DC that there are no mad families. He needed a Mahlo cardinal to do…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2785:field_when:0:208
SUMMARY:Cantor uniqueness along subsequences
DTSTART:2019-03-31T09:00:00
DTEND:2019-03-31T10:00:00
DSCRIPTION:Speaker: Gady Kozma, Weizmann Institute\n
Abstract:
In 1870 Cantor proved that a trigonometric series which converges to zero everywhere must be trivial. In the 50s it was asked: under what conditions is this still true if the convergence is only along a subsequence? We will show a number of results on this topic, hopefully some hints of the proofs will also be showed. Joint work with A. Olevskii.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2787:field_when:0:209
SUMMARY:A Framework for Collective Behavior in Growth-Driven Systems
DTSTART:2019-03-28T11:00:00
DTEND:2019-03-28T12:30:00
DSCRIPTION:Speaker: Yasmine Meroz, The School of Plant Sciences and Food Security at Tel Aviv University\n
Abstract:
A variety of biological systems are not motile, but sessile in nature, relying on growth as the main driver of their movement. Groups of such growing organisms can form complex structures, such as the functional architecture of growing axons, or the adaptive structure of plant root systems. These processes are not yet understood, however the decentralized growth dynamics bear similarities to the collective behavior observed in groups of motile organisms, such as flocks of birds or…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2784:field_when:0:210
SUMMARY:Normal subgroup growth in nilpotent groups
DTSTART:2019-03-27T08:30:00
DTEND:2019-03-27T09:30:00
DSCRIPTION:Speaker: Dr. Michael Schein (Bar-Ilan University)\n
Abstract:
The talk will report on joint work with Angela Carnevale and Christopher Voll and on work in progress with Tomer Bauer.
Let K be a number field with ring of integers O. We explicitly determine the local factors, at all primes unramified in K, of the normal subgroup zeta functions of a large class of finitely generated class-2-nilpotent torsion-free groups over O. This class includes the free class-2-nilpotent groups, various amalgamations of the Heisenberg group, and direct…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2786:field_when:0:211
SUMMARY:Chebyshev-type Quadratures for Doubling Weights
DTSTART:2019-03-25T12:00:00
DTEND:2019-03-25T13:55:00
DSCRIPTION:Speaker: Dr. Shoni Gilboa, The Open University of Israel\n
Abstract:
A Chebyshev-type quadrature for a given weight function is a quadrature formula
with equal weights. We show that a method presented by Kane may be used to determine
the order of magnitude of the minimal number of nodes required in Chebyshev-type
quadratures for doubling weight functions, extending a long line of research on
Chebyshev-type quadratures starting with the 1937 work of Bernstein.
Joint work with Ron Peled.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2728:field_when:0:212
SUMMARY:Variants of the extender algebra and their applications
DTSTART:2019-03-25T11:00:00
DTEND:2019-03-25T13:00:00
DSCRIPTION:Speaker: Ralf Schindler (Universität Münster)\n
Abstract:
In the 1970'ies, Bukowský identified a beautiful and handy criterion for when V is a forcing extension of a given inner model, which proved very useful recently in set theoretical geology. In the 1990'ies, Woodin isolated his extender algebra which makes use of a large cardinal, a Woodin cardinal. It turns out that Bukowský's theorem and Woodin's extender algebra may be presented in a uniform fashion - one proof and one forcing gives both results. We will present the proof and then…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2780:field_when:0:213
SUMMARY:Automorphisms of Weyl Algebra and Conjecture of Kontsevich
DTSTART:2019-03-24T10:00:00
DTEND:2019-03-24T11:00:00
DSCRIPTION:Speaker: Alexei Kanel-Belov, Bar-Ilan University\n
Abstract:
The famous Jacobian Conjecture states that locally invertible polynomial mapping over ${\mathbb C}$ is globally invertible. Dixmier conjecture says that any endomorphism of the ring of differential operators (Weil algebra $A_n$), is an automorphism. In the paper A. Ya. Kanel-Belov and M. L. Kontsevich, "The Jacobian conjecture is stably equivalent to the Dixmier conjecture", Mosc. Math. J., 7:2 (2007), 209-218, arXiv: math0512171. we constructed a homomorphism between the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2767:field_when:0:214
SUMMARY:Intra- vs. inter-group variance in collective behavir
DTSTART:2019-03-14T11:00:00
DTEND:2019-03-14T12:30:00
DSCRIPTION:Speaker: Daniel Knebel\n
Abstract:
Collective motion is the synchronized spatial translation of many individuals concurrently. Its evolutionary importance is emphasized by the wide variety of organisms performing it, ranging from bacteria colonies, to insect swarms, schools of fish, flocks of birds and even human crowds. Thus, collective motion constitutes a key feature in explaining macro-ecological phenomena. In the case of pests such as locusts, understanding the emergence of swarms is also of utmost importance for…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2779:field_when:0:215
SUMMARY:Complex Cellular Structures
DTSTART:2019-03-14T10:00:00
DTEND:2019-03-14T11:00:00
DSCRIPTION:Speaker: Dmitry Novikov, Weizmann Institute\n
Abstract:
Real semialgebraic sets admit so-called cellular decomposition, i.e. representation as a union of cells homeomorphic to cubes. The cell decomposition can be built effectively, and is one of the most powerful tools in studying properties of real semialgebraic sets.
Another most useful tool, the Gromov-Yomdin Lemma, builds a uniform in parameters cover of real algebraic sets by images of $C^r$-smooth mappings of cubes.
There is a non-trivial obstruction to complexification of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2742:field_when:0:216
SUMMARY:The field of definition of the iterates of a rational function
DTSTART:2019-03-13T08:30:00
DTEND:2019-03-13T09:30:00
DSCRIPTION:Speaker: Dr. Solomon Vishkautsan (Tel-Hai Academic College)\n
Abstract:
We will discuss the field of definition of a rational function and in what ways it can change under iteration, in particular when the degree over the base field drops. We present two families of rational functions with the property above, and prove that in the special case of polynomials, only one of these families is possible. We also explain how this relates to Ritt's decomposition theorem on polynomials. Joint work with Francesco Veneziano (SNS Pisa).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2771:field_when:0:217
SUMMARY:New algorithms for convex interpolation
DTSTART:2019-03-11T12:30:00
DTEND:2019-03-11T13:45:00
DSCRIPTION:Speaker: Prof. Jeremy Schiff, Bar-Ilan University\n
Abstract:
In various settings, from computer graphics to financial mathematics, it is necessary
to smoothly interpolate a convex curve from a set of data points. Standard interpolation
schemes do not respect convexity, and existing special purpose methods require arbitrary
choices and/or give interpolants that are very flat between data points. We consider a
broad set of spline-type schemes and show that convexity preservation requires the basic
spline to be infinitely differentiable but…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2770:field_when:0:218
SUMMARY:New algorithms for convex interpolation
DTSTART:2019-03-11T12:30:00
DTEND:2019-03-11T14:00:00
DSCRIPTION:Speaker: Prof. Jeremy Schiff, BIU\n
Abstract:
In various settings, from computer graphics to financial mathematics, it is necessary to smoothly interpolate a convex curve from a set of data points. Standard interpolation schemes do not respect convexity, and existing special purpose methods require arbitrary choices and/or give interpolants that are very flat between data points. We consider a broad set of spline-type schemes and show that convexity preservation requires the basic spline to be infinitely differentiable but…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2766:field_when:0:219
SUMMARY:The Main Gap in the generalized Borel-reducibility hierarchy
DTSTART:2019-03-11T11:00:00
DTEND:2019-03-11T13:00:00
DSCRIPTION:Speaker: Miguel Moreno (BIU)\n
Abstract:
During this talk we will discuss where in the generalized Borel-reducibility hierarchy are the isomorphism relation of first order complete theories. These theories are divided in two kind:classifiable and non-classifiable. To study the classifiable theories case is needed the use of Ehrenfeucht-Fraïssé games. On the other hand the study of the non-classifiable theories is done by using colored trees. The goal of the talk is to see the classifiable theories case and start the non-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2765:field_when:0:220
SUMMARY:New directions in entropy theory
DTSTART:2019-03-10T10:00:00
DTEND:2019-03-10T11:00:00
DSCRIPTION:Speaker: Amos Nevo, the Technion\n
Abstract:
In recent years, the classical theory of entropy for a dynamical system has been revolutionized by the ground-breaking work of several researchers. Two definitions were proposed and developed for actions of general groups : sofic entropy (initiated by L. Bowen) and Rokhlin entropy (initiated by B. Seward). We will start with a very brief account of the latter, and then describe our own recently developed approach to entropy theory for free probability-measure-preserving actions of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2761:field_when:0:221
SUMMARY:Three grand quantum challenges
DTSTART:2019-03-07T11:00:00
DTEND:2019-03-07T12:30:00
DSCRIPTION:Speaker: Emanuele Dalla Torre, physics department BIU\n
Abstract:
In this talk I will describe three computational challenges posed by recent experiments with quantum materials, ultracold atoms, superconducting qubits. The challenges go under the name of "Hubbard model", "Many-body localization", and " Noisy Intermediate-Scale Quantum computers".
END:VEVENT
BEGIN:VEVENT
UID:calendar:2741:field_when:0:222
SUMMARY:Wide simple Lie algebras
DTSTART:2019-03-06T08:30:00
DTEND:2019-03-06T09:30:00
DSCRIPTION:Speaker: Prof. Boris Kunyavski (Bar-Ilan University)\n
Abstract:
We say that a group G is wide if it contains an element which is not representable
as a single commutator of elements of G. Recently it was proven that a finite simple
group cannot be wide, thus confirming a conjecture of Ore of 1950's. On the other hand,
during the past decades there were discovered several examples of wide infinite simple
groups.
In a similar vein, we say that a Lie algebra is wide if it contains an element which is not
representable as a single Lie…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2760:field_when:0:223
SUMMARY:Hardy type inequalities in the category of Hausdorff operators
DTSTART:2019-03-04T12:00:00
DTEND:2019-03-04T13:10:00
DSCRIPTION:Speaker: Prof. E. Liflyand, Bar-Ilan University\n
Abstract:
Classical Hardy's inequalities are concerned with the Hardy operator
and its adjoint, the Bellman operator. Hausdorff operators in their various forms
are natural generalizations of these two operators. We adjust
the scheme used by Bradley for Hardy's inequalities with general weights to the
Hausdorff setting. It is not surprising that the obtained necessary conditions differ
from the sufficient conditions as well as that both depend not only on weights but
also on the kernel that…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2750:field_when:0:224
SUMMARY:Two constructions of gamma spaces
DTSTART:2019-03-04T11:00:00
DTEND:2019-03-04T13:00:00
DSCRIPTION:Speaker: Jialiang He (BIU)\n
Abstract:
An infinite cover of a topological space is an w-cover if every finite subset of this space is contained in some member of the cover, and the whole space is not a member the cover. A cover of a topological space is a gamma-cover if every point of this space belongs to all but finitely many members of this cover. A gamma-space is a space in which every open w-cover contains a gamma-cover.
In this talk, we will present the details how to construct it.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2755:field_when:0:225
SUMMARY:Multiscale substitution schemes and Kakutani sequences of partitions.
DTSTART:2019-03-03T10:00:00
DTEND:2019-03-03T11:00:00
DSCRIPTION:Speaker: Yotam Smilansky, The Hebrew University\n
Abstract:
Substitution schemes provide a classical method for
constructing tilings of Euclidean space. Allowing multiple scales to
appear in the substitution rule, multiscale substitution schemes are
introduced. In the talk we will consider some interesting new
geometric objects which are generated by such multiscale schemes.
We will focus on Kakutani sequences of partitions, in which every
element is defined by the substitution of all tiles of maximal measure
in the previous partition, and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2754:field_when:0:226
SUMMARY:An alternate route to complexity: Trade-off between transcriptome plasticity and genome evolution in cephalopods
DTSTART:2019-02-28T11:00:00
DTEND:2019-02-28T13:30:00
DSCRIPTION:Speaker: Prof. Eli Eisenberg, department of physics, TAU\n
Abstract:
RNA editing is a post-transcriptional process that allows for diversification of proteomes beyond the genomic blueprint, a phenomenon called "recoding". However, it is infrequently used among animals for this purpose. I will review the state-of-the-art understanding of recoding by editing, and discuss at length recent results showing that recoding is particularly common in behaviorally sophisticated coleoid cephalopods. In particular, the trade-off between genome evolution and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2751:field_when:0:227
SUMMARY:A construction of a finitely presented semigroup containing an infinite square-free ideal with zero multiplication
DTSTART:2019-02-27T08:30:00
DTEND:2019-02-27T09:30:00
DSCRIPTION:Speaker: Dr. Sergey Malev (Bar-Ilan University)\n
Abstract:
This work provides an example of a finitely presented semigroup H with zero containing an infinite ideal of the form I = LH, where L is a generator of H, such that every word in generators representing an element of I is square free (i.e. any word of the type LXYYZ, for non-empty Y, equals zero in H).
This is a joint work with Ilya Ivanov-Pogodaev and Olga Sapir.
Keywords: Finitely presented semigroups; nil ideals; nil semigroups; nil rings.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2743:field_when:0:228
SUMMARY:Projective determinacy for games of length $\omega^2$ and longer
DTSTART:2019-02-25T11:00:00
DTEND:2019-02-25T13:00:00
DSCRIPTION:Speaker: Sandra Müller (KGRC)\n
Abstract:
We will study infinite two player games and the large
cardinal strength corresponding to their determinacy. For games of
length $\omega$ this is well understood and there is a tight
connection between the determinacy of projective games and the
existence of canonical inner models with Woodin cardinals. For games
of arbitrary countable length, Itay Neeman proved the determinacy of
analytic games of length $\omega \cdot \theta$ for countable $\theta
\> \omega$ from a sharp…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2749:field_when:0:229
SUMMARY:Discreteness of deformations of co-compact discrete subgroups
DTSTART:2019-02-24T10:00:00
DTEND:2019-02-24T11:00:00
DSCRIPTION:Speaker: Gregory Soifer, Bar-Ilan\n
Abstract:
We prove the discreteness of small deformations of a
discrete co-compact subgroup of the group of isometries of a locally
compact metric space under some natural assumptions.
This is a joint work with G. Margulis.
The talk will be self-contained and should be accessible to master's students.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2748:field_when:0:230
SUMMARY:The strength of very small Jonsson cardinals
DTSTART:2019-02-18T11:00:00
DTEND:2019-02-18T13:00:00
DSCRIPTION:Speaker: Dominik Adolf (BIU)\n
Abstract:
An uncountable cardinal κ is Jonnson if only if the set of proper subsets of κ that are of cardinality κ is stationary. Though this property has large cardinal strength it is not at all clear that Jonnson cardinals do in fact need to be large in the obvious sense. For example, it is known that Jonsson cardinals can be singular.
In this talk we will use the methods of Inner Model Theory to show that, given the assumption that the least singular cardinal is Jonsson, there is a…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2744:field_when:0:231
SUMMARY:On Tame Subgroups of Finitely Presented Groups
DTSTART:2019-02-17T10:00:00
DTEND:2019-02-17T11:00:00
DSCRIPTION:Speaker: Dr. Rita Gitik, Department of Mathematics, University of Michigan\n
Abstract:
We describe several examples of tame subgroups of finitely presented groups and prove that the fundamental groups of certain finite graphs of groups are locally tame.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2699:field_when:0:232
SUMMARY:Uniformization properties and graph edge colourings
DTSTART:2019-02-11T11:00:00
DTEND:2019-02-11T13:00:00
DSCRIPTION:Speaker: Daniel T. Soukup (KGRC)\n
Abstract:
Sierpinski's now classical result states that there is an edge 2-colouring of the complete graph on aleph1 vertices so that there are no uncountable monochromatic subgraphs. In the 1970s, Erdos, Galvin and Hajnal asked what other graphs with large chromatic number admit similar edge colourings i.e., with no 'large' monochromatic subgraphs. We plan to review some recent advances on this problem and in particular, connect the question to Shelah's ladder system uniformization theory.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2783:field_when:0:233
SUMMARY:מונחים לציון חודשים חסרים ומלאים ביהדות העתיקה
DTSTART:2019-02-05T15:30:00
DTEND:2019-02-05T17:00:00
DSCRIPTION:Speaker: ד"ר אשבל רצון\n
Abstract:
בלוחות ירחיים חלק מן החודשים הם בני 29 ימים ואחרים הם בני 30 ימים. בעברית המודרנית אנו מציינים את הסוג הקצר בשם חודש חסר, ואת הסוג הארוך בשם חודש מלא. מונחים אלה מופיעים לראשונה בתלמוד. בהרצאה אנסה לטעון כי ניתן לשחזר שימוש במונח "חודש חסר" כבר בנוסח הארמי של ספר המאורות שנמצא בקומראן. זהו ספר אסטרונומי מן המאה השלישית לפני הספירה לערך, שבין היתר המנסה לסנכרן בין לוח ירחי אידיאלי ללוח שמשי אידיאלי בן 364 ימים שהיה מקובל מאוחר יותר בכת קומראן. המצאותו של המונח בספר קדום כל כך היא…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2698:field_when:0:234
SUMMARY:Selection Principles in Mathematics (an overview)
DTSTART:2019-02-04T11:00:00
DTEND:2019-02-04T13:00:00
DSCRIPTION:Speaker: Piotr Szewczak, Cardinal Stefan Wyszyński University in Warsaw, Poland\n
Abstract:
The theory of selection principles deals with the possibility of obtaining mathematically significant objects by selecting elements from sequences of sets. The studied properties mainly include covering properties, measure- and category-theoretic properties, and local properties in topological spaces, especially functions spaces. Often, the characterization of a mathematical property using a selection principle is a nontrivial task leading to new insights on the characterized…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2745:field_when:0:235
SUMMARY:The geometry of almost-commuting varieties with a flag
DTSTART:2019-01-30T08:30:00
DTEND:2019-01-30T09:30:00
DSCRIPTION:Speaker: Prof. Mee Seong Im (United States Military Academy)\n
Abstract:
In the construction of Hamiltonian reductions in symplectic geometry, interesting and rich connections to Hilbert schemes, Calogero-Moser spaces, and rational spherical Cherednik algebras have emerged over the last two decades. A Borel analogue of the classical general linear group construction (realized after a reduction from the cotangent bundle of enhanced Grothendieck-Springer resolutions) potentially opens doors for its connections to isospectral Hilbert schemes, flag Hilbert…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2764:field_when:0:236
SUMMARY:הנוסחאות המתימטיות של הרמב"ם לחישובי קידוש החודש
DTSTART:2019-01-29T15:30:00
DTEND:2019-01-29T17:00:00
DSCRIPTION:Speaker: הרב איתן צקוני\n
Abstract:
א. נוסחת מנת מסלול השמש (נספחים לספר חזון שמים עמוד 9 מהדורה חמישית)
ב. נוסחת אורך חצי היום (כנ"ל עמוד 10)
ג. נוסחת התוספת על אמצע מסלול הירח (עמוד 12)
ד. נוסחת מנת המסלול הנכון (עמוד 13)
ה. נוסחת שינוי מראה הגובה (עמוד 14)
ו. סקירת השיטות השונות של חישוב זמני היום בהלכה המקובלות בזמננו.
ז. תצוגה של תוכנת הצג החכם.
להרצאה המצולמת
למצגת ההרצאה
END:VEVENT
BEGIN:VEVENT
UID:calendar:2740:field_when:0:237
SUMMARY:Stability of some super-resolution problems
DTSTART:2019-01-24T09:00:00
DTEND:2019-01-24T10:30:00
DSCRIPTION:Speaker: Dmitry Batenkov from MIT\n
Abstract:
The problem of computational super-resolution asks to recover fine
features of a signal from inaccurate and bandlimited data, using an
a-priori model as a regularization. I will describe several
situations for which sharp bounds for stable reconstruction are known,
depending on signal complexity, noise/uncertainty level, and available
data bandwidth. I will also discuss optimal recovery algorithms, and
some open questions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2739:field_when:0:238
SUMMARY:Simple juntas for shifted families
DTSTART:2019-01-20T12:00:00
DTEND:2019-01-20T13:30:00
DSCRIPTION:Speaker: Andrey Kupavskii (Oxford and MIPT Moscow)\n
Abstract:
We say that a family F of k-element sets is a j-junta if there is a set J of size j such that, for any set, its presence in F depends on its intersection with J only. Approximating arbitrary families by j-juntas with small j is a recent powerful technique in extremal set theory.
The weak point of all known approximation by juntas results is that they work in the range n>Ck, where C is an extremely fast growing function of the input parameters. In this talk, we present a simple and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2679:field_when:0:239
SUMMARY:On binary quadratic forms (a few open problems of C. F. Gauss).
DTSTART:2019-01-16T09:00:00
DTEND:2019-01-16T10:00:00
DSCRIPTION:Speaker: Prof. Boris Z. Moroz (Moscow Institute of Physics and Technology and University of Bonn)\n
Abstract:
I shall describe some open problems, relating to representation
of integers by integral binary quadratic forms: new things are just
well forgotten old ones !
END:VEVENT
BEGIN:VEVENT
UID:calendar:2714:field_when:0:240
SUMMARY:Virtually all polynomials are irreducible
DTSTART:2019-01-16T08:00:00
DTEND:2019-01-16T09:00:00
DSCRIPTION:Speaker: Prof. Lior Bary-Soroker (Tel Aviv University)\n
Abstract:
It has been known for almost a hundred years that most polynomials with integral coefficients are irreducible and have a big Galois group.
For a few dozen years, people have been interested in whether the same holds when one considers sparse families of polynomials—notably, polynomials with plus-minus 1 coefficients.
In particular, “some guy on the street” conjectures that the probability for a random plus-minus 1 coefficient polynomial to be irreducible tends to 1 as the degree…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2734:field_when:0:241
SUMMARY:"דברים שאי אפשר הרצאה רביעית בסדרת "חור בהשכלה
DTSTART:2019-01-14T16:00:00
DTEND:2019-01-14T18:00:00
DSCRIPTION:Speaker: פרופ' עוזי וישנה\n
Abstract:
END:VEVENT
BEGIN:VEVENT
UID:calendar:2735:field_when:0:242
SUMMARY:Hankel transforms and general monotonicity
DTSTART:2019-01-14T12:00:00
DTEND:2019-01-14T13:15:00
DSCRIPTION:Speaker: Dr. A. Debernardi, Bar-Ilan University\n
Abstract:
We will discuss some problems related to Hankel transforms of \textbf{real-valued} general monotone functions,
some of them generalize previously known results, and some others are completely new. To mention some, we give
a criterion for uniform convergence of Hankel transforms, and we also give a solution to Boas' problem in this
context. In particular, the latter implies a generalization of the well-known Hardy-Littlewood inequality for
Fourier transforms.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2733:field_when:0:243
SUMMARY:An introduction to generalized descriptive set theory, part 4
DTSTART:2019-01-14T11:00:00
DTEND:2019-01-14T13:00:00
DSCRIPTION:Speaker: Miguel Moreno (BIU)\n
Abstract:
Last week, we gave a detailed proof of Lemma 1.13 from the notes:http://u.math.biu.ac.il/~morenom3/GDST-2018.pdf
This week, we shall continue, proving that, if V=L, then $\kappa$-Borel* class is equal to the $\Sigma1^ 1(\kappa)$ class.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2727:field_when:0:244
SUMMARY:Democratic fair allocation
DTSTART:2019-01-13T12:00:00
DTEND:2019-01-13T13:30:00
DSCRIPTION:Speaker: Erel Segal-Halevi (Ariel University)\n
Abstract:
Several items have to be allocated among several families. In each family, there are members with different preferences over the items. The goal is to divide the items such that, in each family, as many members as possible will perceive the division as "fair".
I will show that this problem combines two seemingly-unrelated problems: fair allocation of items among individuals, and finding winning-strategies in combinatorial games. I will present division algorithms, upper bounds and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2933:field_when:0:245
SUMMARY:Interfacial dynamics of dissolving objects in fluid flow
DTSTART:2019-01-09T12:00:00
DTEND:2019-01-09T13:00:00
DSCRIPTION:Speaker: (Chris H. Rycroft (Harvard\n
Abstract:
Title: Interfacial dynamics of dissolving objects in fluid flow
Abstract:
An advection–diffusion-limited dissolution model of an object being eroded by a two-dimensional potential flow will be presented. By taking advantage of conformal invariance of the model, a numerical method will be introduced that tracks the evolution of the object boundary in terms of a time-dependent Laurent series. Simulations of several dissolving objects will be shown, all of which show collapse to a single…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2710:field_when:0:246
SUMMARY:Ambidexterity in stable infinity categories
DTSTART:2019-01-09T08:30:00
DTEND:2019-01-09T09:30:00
DSCRIPTION:Speaker: Shachar Carmeli (Weizmann Institute of Science)\n
Abstract:
If G is a finite group and M is a G-module, there is a norm map from the homology of G with coefficients in M to the cohomology. This map arises from a morphism in the derived category from the derived co-invariants to the derived invariants of G.
The resulting map is always an isomorphism over the rational numbers but rarely an isomorphism in mod p representation. In stable homotopy theory, there are many "intermediate" characteristics (p.n) associated with the so called "Morava K-…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2711:field_when:0:247
SUMMARY:גלי קול, אור ותקשורת
DTSTART:2019-01-07T16:00:00
DTEND:2019-01-07T18:00:00
DSCRIPTION:Speaker: ד"ר ארז שיינר\n
Abstract:
END:VEVENT
BEGIN:VEVENT
UID:calendar:2713:field_when:0:248
SUMMARY:Nonlinear resolvent of holomorphic generators
DTSTART:2019-01-07T12:00:00
DTEND:2019-01-07T13:45:00
DSCRIPTION:Speaker: Prof. David Shoikhet, Holon Institute of Technology, Israel\n
Abstract:
This talk is based on joint work with Mark Elin and Toshiyuki Sugawa. Let $f$
\ be the infinitesimal generator of a one-parameter semigroup $\left\{
F_{t}\right\} _{t>0}$ of holomorphic self-mappings of the open unit disk,
i.e., $f=\lim_{t\rightarrow 0}\frac{1}{t}\left( I-F_{t}\right) .$ In this
work, we study properties of the resolvent family $R=\left\{ \left(
I+rf\right) ^{-1}\right\} _{r>0}$ \ in the spirit of geometric function
theory. We discovered, in particular, that $R…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2712:field_when:0:249
SUMMARY:An introduction to generalized descriptive set theory, part 3
DTSTART:2019-01-07T11:00:00
DTEND:2019-01-07T13:00:00
DSCRIPTION:Speaker: Miguel Moreno (BIU)\n
Abstract:
After introducing the notions of $\kappa$-Borel class, $\kappa$-$\Delta_1^1$ class, $\kappa$-Borel^* class we saw some subset relations between them in the previous talk ( http://u.math.biu.ac.il/~morenom3/GDST-2018.pdf ). We finished the previous talk with a sketch of the proof of:
if V=L, then $\kappa$-Borel* class is equal to the $\Sigma1^ 1(\kappa)$ class.
We will see this proof in complete detail, starting from the key lemma, Lemma 1.13 on the notes.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2708:field_when:0:250
SUMMARY:An algebraic proof of a conjecture of Erdos and Purdy
DTSTART:2019-01-06T12:00:00
DTEND:2019-01-06T13:30:00
DSCRIPTION:Speaker: Rom Pinchasi (Technion)\n
Abstract:
Erdos and Purdy conjectured that for n \geq 5 one cannot find a set of n red points in general position and another set of n-1 blue points such that every line determined by two red points passes also through a blue point. This conjecture is trivially true for n odd, but turns to be very challenging for n even. The conjecture is, in fact, a special (but important) case of the Magic Configuration conjecture of Murty from 1971. The conjecture of Murty was proved in 2008 in a topological…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2709:field_when:0:251
SUMMARY:"קל, קשה ובלתי אפשרי: P, NP וחבריהן" הרצאה שלישית בסדרה "מה עושים עם זה"
DTSTART:2019-01-02T13:00:00
DTEND:2019-01-02T14:00:00
DSCRIPTION:Speaker: פרופ' ראובן כהן\n
Abstract:
END:VEVENT
BEGIN:VEVENT
UID:calendar:2703:field_when:0:252
SUMMARY:Irreducibility of Galois representations
DTSTART:2019-01-02T08:30:00
DTEND:2019-01-02T09:30:00
DSCRIPTION:Speaker: Ariel Weiss (University of Sheffield)\n
Abstract:
According to the Langlands philosophy, there should be a close relationship between automorphic representations and Galois representations. When are these Galois representations irreducible?
In the 1970s, Ribet proved that the p-adic Galois representation attached to a modular form f is irreducible if and only if f is cuspidal. More generally, it is conjectured that the p-adic Galois representation associated to any cuspidal automorphic representation of GL(n) is irreducible.
The…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2691:field_when:0:253
SUMMARY:An introduction to generalized descriptive set theory, part 2
DTSTART:2018-12-31T11:00:00
DTEND:2018-12-31T13:00:00
DSCRIPTION:Speaker: Miguel Moreno (BIU) \n
Abstract:
After introducing the notions of $\kappa$-Borel class, $\kappa$-$\Delta_1^1$ class, $\kappa$-Borel^* class in the previous talk ( http://u.math.biu.ac.il/~morenom3/GDST-2018.pdf ), in this talk, we will show the relation between this classes.
In descriptive set theory the Borel class, the $\Delta_1^1$ class, the Borel* class are the same class, this doesn't hold in the generalized descriptive set theory, in particular under the assumption V=L the Borel* class is equal to the $\Sigma1…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2704:field_when:0:254
SUMMARY:Learning and counting
DTSTART:2018-12-30T12:00:00
DTEND:2018-12-30T13:30:00
DSCRIPTION:Speaker: Ido Nachum (Technion)\n
Abstract:
A map $Y: X \rightarrow \{+1, -1\}$ over a finite set $X \con R^d $ is (linearly) separable if there exists $w \in R^d$ such that $\sign(w \bigcdot x)=Y(x)$ for all $x \in X$. When the Euclidean norm of $w$ is $\|w\|=1$, the number $\marg (w,Y) = \min_{x \in X} {Y(x) w\bigcdot x }$ is the margin of $w$ with respect to $Y$. The number $\marg(Y) = \sup_{w \in R^d : \|w\|=1} \marg(w,Y)$ is the margin of $Y$. We call $Y$ an $\eps$-partition if its margin is at least $\eps$.
Given a set $…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2705:field_when:0:255
SUMMARY:בניינים - כשחבורה מחפשת גאומטריה ומוצאת קומבינטוריקה
DTSTART:2018-12-26T13:00:00
DTEND:2018-12-26T14:00:00
DSCRIPTION:Speaker: פרופ' עוזי וישנה\n
Abstract:
END:VEVENT
BEGIN:VEVENT
UID:calendar:2683:field_when:0:256
SUMMARY:Optimal assignments with supervisions
DTSTART:2018-12-26T08:30:00
DTEND:2018-12-26T09:30:00
DSCRIPTION:Speaker: Dr. Adi Niv (Kibbutzim College of Education, Technology, and the Arts)\n
Abstract:
In this talk I provide a graph-theoretic proof of the tropical Jacobi identity, alternative
to the matrix-theoretic proof recently obtained jointly with Akian and Gaubert. The latter was inspired by the classical identity:
The (J^c,I^c)-minor of a matrix A corresponds, in some way to be defined, to the (I,J)-minor of A^{-1}).
That is, the compound of order k of A corresponds to the compound of order (n-k) of its inverse.
We provide an application of this theorem to optimal…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2752:field_when:0:257
SUMMARY:המולדות המדוייקים העקרונות עליהם מבוסס הלוח העברי
DTSTART:2018-12-25T15:30:00
DTEND:2018-12-25T16:45:00
DSCRIPTION:Speaker: ד"ר מוטי שלם, סמנכ״ל תוכן ופיתוח, מכון שם עולם\n
Abstract:
1. הלוח העברי עד לחורבן הבית השני. מתוך מקורות המבוססים על המגילות הגנוזות.
2. מחקרה של הפרופ׳ רחל אליאור והביקורת עליו.
3. הלוח הנוהג מתקופה המשנה והתלמוד ועד ימינו. נתוני רקע קצרים והבהרת מושגים.
4. חישוב המולד המקובל והמולד המדוייק הנוהג בקהילת הבבלים ומשמעותו בסוגיית ברכת הלבנה.
להרצאה המצולמת
למצגת ההרצאה
END:VEVENT
BEGIN:VEVENT
UID:calendar:2702:field_when:0:258
SUMMARY:Noise Stability and Majority Functions
DTSTART:2018-12-24T12:00:00
DTEND:2018-12-24T13:25:00
DSCRIPTION:Speaker: Prof. Elchanan Mossel, Massachusets Institute of Technology, USA\n
Abstract:
Two important results in Boolean analysis highlight the role of majority functions in the theory
of noise stability. Benjamini, Kalai, and Schramm (1999) showed that a boolean monotone function
is noise-stable if and only if it is correlated with a weighted majority. Mossel, O’Donnell, and
Oleszkiewicz (2010) showed that simple majorities asymptotically maximize noise stability among
low influence functions. In the talk, we will discuss and review progress from the last decade
in our…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2693:field_when:0:259
SUMMARY:Degree anti-Ramsey numbers
DTSTART:2018-12-23T12:00:00
DTEND:2018-12-23T13:30:00
DSCRIPTION:Speaker: Shoni Gilboa (Open University)\n
Abstract:
The degree anti-Ramsey number of a graph H is the smallest integer k for which there exists a graph G with maximum degree at most k such that any proper edge colouring of G yields a rainbow copy of H (i.e., all edges of this copy of H have distinct colours).
We determine the degree anti-Ramsey number of any tree, and then extend this to any forest using a classical result of Bollobas concerning cross intersecting families. We also use a topological version of Hall's Theorem due to…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2678:field_when:0:260
SUMMARY:Point counting for foliations over number fields
DTSTART:2018-12-19T08:30:00
DTEND:2018-12-19T09:30:00
DSCRIPTION:Speaker: Dr. Gal Binyamini (Weizmann Institute of Science)\n
Abstract:
A foliation subdivides a manifold $M$ into a union of "leafs". It is usually defined by specifying a "distribution": a choice of tangent space at every point of $M$. Going from a distribution to a leaf tangent to it amounts to solving a differential equation, and the leafs are therefore usually transcendental objects.
Consider the case that $M$ and the distribution are algeraic over a number field. We give bounds for the number of intersections between a leaf of the foliation and an…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2684:field_when:0:261
SUMMARY:מה בעצם עשה זאן בטיסט ז'וזף פורייה? הרצאה שלישת בסדרת "חור בהשכלה"
DTSTART:2018-12-17T16:00:00
DTEND:2018-12-17T18:00:00
DSCRIPTION:Speaker: פרופ' ג'רמי שיף\n
Abstract:
סטודנטים למתמטיקה פיזיקה והנדסה(וגם למקצועות אחרים) מקדישים זמן רב ללימוד טורי פורייה וטרנספורם פורייה והישומים שלהם.
אנליזת פורייה (הנקראת גם "אנליזה הרמונית") תוארה מחד ככלי החזק ביותר בארגז הכלים של המתמטיקה האנליטית, ומאידך כדרכו של הטבע לנתח נתונים: העיניים והאוזניים שלנו מחשבות טרנספורם פורייה הרבה לפני שאנו לומדים על כך באוניברסיטה.
בניגוד להמלצה של מדענים שאמרו ששום מידה של הסברים לא יכולה להסביר כראוי את החשיבות של טרנספורם פורייה, אני אנסה בהרצאה להסביר מהו הדבר הזה מבחינה…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2692:field_when:0:262
SUMMARY:On a local version of the fifth Busemann-Petty Problem
DTSTART:2018-12-17T12:00:00
DTEND:2018-12-17T13:30:00
DSCRIPTION:Speaker: Prof. D. Ryabogin, Kent State University, Ohio, USA\n
Abstract:
In 1956, Busemann and Petty posed a series of questions about
symmetric convex bodies, of which only the first one has been solved.
Their fifth problem asks the following.
Let K be an origin symmetric convex body in the n-dimensional Euclidean
space and let H_x be a hyperplane passing through the origin orthogonal to
a unit direction x. Consider a hyperplane G parallel to H_x and supporting
to K and let C(K,x)=vol(K\cap H_x)dist (0, G).
If there exists a constant C…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2632:field_when:0:263
SUMMARY:On countable unions of countable sets
DTSTART:2018-12-17T11:00:00
DTEND:2018-12-17T13:00:00
DSCRIPTION:Speaker: Asaf Karagila (UEA)\n
Abstract:
How big can countable unions of countable sets be? Assuming the axiom of choice, countable. Not assuming the axiom of choice, it is not hard to arrange situation where there are many incomparable cardinals which are the countable union of countable sets. But none of them are "particularly large". While a countable union of countable sets can at most be mapped onto \omega_1, its power set can be made much larger. We prove an old (and nearly forgotten) theorem of Douglass Morris, that…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2682:field_when:0:264
SUMMARY:Topology and combinatorics of the complex of flags
DTSTART:2018-12-16T12:00:00
DTEND:2018-12-16T13:30:00
DSCRIPTION:Speaker: Roy Meshulam (Technion)\n
Abstract:
Let V be an n-dimensional space over a fixed finite field. The complex of flags X(V) is the simplicial complex whose vertices are the non-trivial linear subspaces of V, and whose simplices are ascending chains of subspaces. This complex, also known as the spherical building associated to the linear group GL(V), appears in a number of different mathematical areas, including topology, combinatorics and representation theory. After recalling the classical homological properties of X(V),…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2677:field_when:0:265
SUMMARY:Structure of degenerate principal series of exceptional groups
DTSTART:2018-12-12T08:30:00
DTEND:2018-12-12T09:30:00
DSCRIPTION:Speaker: Dr. Avner Segal (Bar-Ilan University)\n
Abstract:
The reducibility and structure of parabolic inductions is a basic problem in the representation theory of p-adic groups. Of particular interest are principal series and degenerate principal series representations, that is parabolic induction of 1-dimensional representations of Levi subgroups.
In this talk, I will start by describing the functor of normalized induction and its left adjoint, the Jacquet functor, and by going through several examples in the group SL_4(Q_p) will…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2676:field_when:0:266
SUMMARY:אי שיוויון הממוצעים
DTSTART:2018-12-10T16:00:00
DTEND:2018-12-10T18:00:00
DSCRIPTION:Speaker: ד"ר ארז שיינר\n
Abstract:
הממוצע ההרמוני קטן או שווה לממוצע ההנדסי, שקטן או שווה לממוצע החשבוני.
בהרצאה זו נוכיח טענה זו, ונראה כיצד השימוש בה מהווה שיטה מרכזית בעולם המתמטיקה.
בעזרת אי שיוויון הממוצעים נפתור שאלות גיאומטריות, נגדיר את המספר e, נוכיח את כלל המנה ונוכיח את אי-שיוויון ברנולי ואי-שיוויון קושי-שוורץ.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2681:field_when:0:267
SUMMARY:Multivariable Hardy spaces and the classification of universal dilation algebras
DTSTART:2018-12-10T13:05:00
DTEND:2018-12-10T14:00:00
DSCRIPTION:Speaker: Dr. Eli Shamovich, University of Waterloo, Waterloo, Ontario, Canada\n
Abstract:
In this talk, we will discuss what is special about the Hardy spaces $H^2(\mathbb{D})$ and its
multiplier algebra $H^{\infty}(\mathbb{D})$, from the point of view of operators algebras and
function theory. I will present two generalizations of the pair $H^2$ and $H^{\infty}$ to the
multivariable setting. One commutative and one noncommutative. We will then discuss a natural
classification question that arises in the multivariable setups of algebras of analytic functions
on…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2680:field_when:0:268
SUMMARY:Radon Transforms over Horospheres in Real Hyperbolic Space
DTSTART:2018-12-10T12:00:00
DTEND:2018-12-10T13:00:00
DSCRIPTION:Speaker: Prof. Boris Rubin, Louisiana State University, USA\n
Abstract:
The horospherical Radon transform integrates functions on the n-dimensional real
hyperbolic space over d-dimensional horospheres, where d is a fixed integer, $1\le d\le n-1$.
Using the tools of real analysis, we obtain sharp existence conditions and explicit inversion
formulas for these transforms acting on smooth functions and functions belonging to $L^p$. The
case d = n-1 agrees with the classical Gelfand-Graev transform which was studied before in
terms of the distribution theory…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2675:field_when:0:269
SUMMARY:An introduction to generalized descriptive set theory, part 1
DTSTART:2018-12-10T11:00:00
DTEND:2018-12-10T13:00:00
DSCRIPTION:Speaker: Miguel Moreno (BIU) \n
Abstract:
This is the first of many of talks in which an overview of the Borel-reducibility hierarchy in the generalized Baire space will be given. The aim of this talk is to introduce the notions of $\kappa$-Borel class, $\kappa$-$\Delta_1^1$ class, $\kappa$-Borel^* class, and show the relation between these classes.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2674:field_when:0:270
SUMMARY:פירוק גרפים למעגלים ותכנון מסלולי נסיעה הרצאה שניה בסגרה מה עושים עם זה
DTSTART:2018-12-04T22:05:00
DTEND:2018-12-05T14:00:00
DSCRIPTION:Speaker: ד"ר שימי הבר\n
Abstract:
הקמפוסים של אוניברסיטת ג'יין בהודו (Jain University) פרושים בכל רחבי בנגלור רבתי. האוניברסיטה הציעה לסטודנטים ולחברי הסגל שירות הסעות בין המחלקות, כיתות הלימוד והמעונות בעזרת עשרה אוטובוסים. מסלולי האוטובוסים נקבעו על ידי אנשי האוניברסיטה והנהגים באופן ידני. בסקר שנערך ב 2010 בין משתמשי השירות עלתה תמונה של חוסר שביעות רצון מזמני ההמתנה, אורך הנסיעות וזמינות האוטובוסים. בעקבות הסקר תוכננו מסלולי ההסעות מחדש ע"י חבר סגל מהמחלקה להנדסה בשיתוף עם שני מתמטיקאים. לאחר השינוי נדרשו רק שבעה…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2673:field_when:0:271
SUMMARY:Finite sums of ridge functions on convex subsets of R^n
DTSTART:2018-12-03T12:00:00
DTEND:2018-12-03T13:10:00
DSCRIPTION:Speaker: Dr. A. Kuleshov, Moscow State University, Russia\n
Abstract:
We prove that each function of one variable forming a continuous finite sum of ridge functions
on a convex body belongs to the VMO space on every compact interval of its domain. Also, we prove that for the existence of finite limits of the functions of one variable forming the sum at the
corresponding boundary points of their domains, it suffices to assume the Dini condition on the
modulus of continuity of some continuous sum of ridge functions on a convex body E at some boundary…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2670:field_when:0:272
SUMMARY:חבורת בראוור, הרצאה שניה בסדרה "מתמטיקה של גדולים"
DTSTART:2018-11-28T13:00:00
DTEND:2018-11-28T14:00:00
DSCRIPTION:Speaker: פרופ' עוזי וישנה\n
Abstract:
חבורת בראוור, המתארת את האלגברות הפשוטות מעל שדה, היא אובייקט מרכזי באלגברה, אריתמטיקה וגאומטריה. בהרצאה נפתח את הכלים הנחוצים להגדרת האובייקט הזה, ונלמד להכיר אותו בכמה מקרים מיוחדים.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2668:field_when:0:273
SUMMARY:Towards a group-like small cancellation theory for rings
DTSTART:2018-11-28T08:30:00
DTEND:2018-11-28T09:30:00
DSCRIPTION:Speaker: Dr. Agatha Atkarskaya (Bar-Ilan University)\n
Abstract:
Let a group G be given by generators and defining relations. It is known that we cannot, in general, extract specific information about the structure of G using the defining relations. However, if the defining relations satisfy small cancellation conditions, then we possess a great deal of knowledge about G. In particular, such groups are hyperbolic, that is, we can express the multiplication in the group by means of thin triangles. It seems of interest to develop a similar theory for…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2669:field_when:0:274
SUMMARY:The Fourier transform of a convex function revisited
DTSTART:2018-11-26T12:00:00
DTEND:2018-11-26T13:50:00
DSCRIPTION:Speaker: Prof. E. Liflyand, Bar-Ilan University\n
Abstract:
Asymptotic-wise results for the Fourier transform of a function of convex type are proved.
Certain refinement of known one-dimensional results due to Trigub gives a possibility to
obtain their multidimensional generalizations.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2659:field_when:0:275
SUMMARY:Stationary Reflection from subcompactness
DTSTART:2018-11-26T11:00:00
DTEND:2018-11-26T13:00:00
DSCRIPTION:Speaker: Yair Hayut (HUJI)\n
Abstract:
We discuss a joint work with Unger about stationary reflection at subcompact cardinals and the consistency of stationary reflection at successor of singular cardinal from a $Pi^1_1$-$kappa^+$-subcompact cardinal.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2666:field_when:0:276
SUMMARY:Simple connectivity in random 2-complexes
DTSTART:2018-11-25T12:00:00
DTEND:2018-11-25T13:30:00
DSCRIPTION:Speaker: Zur Luria (JCE)\n
Abstract:
The random Linial-Meshulam complex Y_d(n,p) is the higher-dimensional analogue of the random graph model G(n,p). In recent years, the properties of random hypergraphs and simplicial complexes have been studied intensively. In this talk, we consider the fundamental group of a random 2-dimensional simplicial complex.
Babson, Hoffman and Kahle proved that the threshold for the fundamental group to vanish, i.e. simple connectivity, is approximately p=n^(-1/2). We show that in fact this…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2663:field_when:0:277
SUMMARY:Automorphisms of the category of free finitely generated algebras
DTSTART:2018-11-21T08:30:00
DTEND:2018-11-21T09:30:00
DSCRIPTION:Speaker: Dr. Elena Aladova (Universidade Federal do Rio Grande do Norte)\n
Abstract:
One of the natural questions of Universal Algebraic Geometry is the following one: when do two algebras from a variety of algebras have the same algebraic geometry?
This question can be interpreted in various ways. For instance, one can say that algebraic geometries of the algebras are the same if the categories of algebraic sets over the given algebras are isomorphic.
An important role in the study of the categories of algebraic sets is played by investigations of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2664:field_when:0:278
SUMMARY:מערכות מספרים – מהשלמים ועד הקווטרניונים והאוקטוניונים
DTSTART:2018-11-19T16:00:00
DTEND:2018-11-19T17:30:00
DSCRIPTION:Speaker: פרופ' עוזי וישנה\n
Abstract:
מערכות מספרים הן בין הישויות המתמטיות הבסיסיות ביותר: המספרים הטבעיים, השלמים, הרציונליים, הממשיים, המרוכבים. נסקור את ההתפתחות של המערכות האלה ואת המאפיינים הייחודיים שלהן, ונראה איך מערכות מוכרות פחות, כגון הקווטרניונים והאוקטוניונים, משתלבות בסיפור.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2661:field_when:0:279
SUMMARY:Selection covering properties and Cohen reals, part 2
DTSTART:2018-11-19T11:00:00
DTEND:2018-11-19T13:00:00
DSCRIPTION:Speaker: JiaLiang He (BIU)\n
Abstract:
We will address preservation theorems under Cohen forcing for various selection covering properties (Menger, Hurewicz, Rothberger and Gamma property).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2662:field_when:0:280
SUMMARY:The threshold problem for Latin squares
DTSTART:2018-11-18T12:00:00
DTEND:2018-11-18T13:30:00
DSCRIPTION:Speaker: Michael Simkin (Hebrew University of Jerusalem)\n
Abstract:
An order-$n$ Latin square is equivalent to a triangle-decomposition of the complete tripartite hypergraph $K_{n,n,n}$. Let $H \sim H_3(n,n,n;p)$ be a tripartite, balanced, binomial random $3$-uniform hypergraph on $3n$ vertices where each edge is present with probability $p$. What is the threshold $p$ for the property that $H$ contains a Latin square? The general heuristic is that spanning structures appear together with the disappearance of local obstructions. Thus the natural…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2652:field_when:0:281
SUMMARY:Factorization of tensor products of modules over infinite dimensional Lie algebras
DTSTART:2018-11-14T08:30:00
DTEND:2018-11-14T09:30:00
DSCRIPTION:Speaker: Dr. Shifra Reif (Bar-Ilan University)\n
Abstract:
A classical theorem of Rajan states that a tensor product of simple finite-dimensional modules over a simple Lie algebra admits unique factorization. In this talk, we shall discuss various types of infinite dimensional Lie algebras and the factorization of tensor products for these algebras. Joint with Venkatesh.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2660:field_when:0:282
SUMMARY:Completely monotonic gamma ratio and infinitely divisible H-function of Fox
DTSTART:2018-11-12T12:00:00
DTEND:2018-11-12T13:25:00
DSCRIPTION:Speaker: Prof. Dmitry Karp, Institute of Applied Mathematics, Far Eastern Branch of Russian Academy of Sciences, Russia\n
Abstract:
We investigate conditions for the logarithmic complete
monotonicity of a quotient of two products of gamma functions, where
the argument of each gamma function has a different scaling factor. We
give necessary and sufficient conditions in terms of non-negativity of
some elementary functions and some more practical sufficient
conditions in terms of parameters. Further, we study the representing
measure in Bernstein’s theorem for both equal and non-equal scaling
factors. This leads to…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2633:field_when:0:283
SUMMARY:Selection covering properties and Cohen reals, part 1
DTSTART:2018-11-12T11:00:00
DTEND:2018-11-12T13:00:00
DSCRIPTION:Speaker: JiaLiang He (BIU)\n
Abstract:
We will introduce four selection covering properties (Menger, Hurewicz, Rothberger and Gamma property), and consider preserving results on these properties under Cohen forcing.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2658:field_when:0:284
SUMMARY:Helly type theorems for open connected sets in the plane
DTSTART:2018-11-11T12:00:00
DTEND:2018-11-11T13:30:00
DSCRIPTION:Speaker: Minki Kim (Technion)\n
Abstract:
Helly's theorem is a classical result in combinatorial geometry about the intersection patterns of convex sets in Euclidean spaces. For the 2-dimensional case, it asserts that for a family of convex sets in the plane, if every 3 members have a point in common, then all members in the family have a point in common. The topological Helly theorem, also proved by Helly, shows that the same assertion holds for a family of open and contractible sets where each intersection is again open and…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2657:field_when:0:285
SUMMARY:כשתורת הגרפים פגשה משוואות דיפרנציאליות הרצאה ראשונה בסדרה מה עושים עם זה
DTSTART:2018-11-07T13:00:00
DTEND:2018-11-07T14:00:00
DSCRIPTION:Speaker: ד"ר ברוך ברזל \n
Abstract:
כמה אנשים דרושים כדי להחליף נורה?
התשובה הרצינית אומרת שדרושים עשרות אלפים. החל מהמוכר בחנות מוצרי החשמל, דרך נהגת המשאית שהובילה את המנורות, יצרני הזכוכית, חרשי המתכת, כורי הנחושת...
אם כן, החלפת מנורה, הזמנת כוס בירה, גלישה באינטרנט - כמעט כל פעולה שאנו עושים - היא תוצאה של שיתוף פעולה של המוני בני אדם.
אך כמה מאיתנו באמת מרגישים חלק משיתוף פעולה המוני וחוצה יבשות שכזה? מי מנהיג את שיתוף הפעולה הזה? הרי בלעדיו - לא היו לנו מנורות להחליף. או בירה.
למעשה, שיתופי פעולה שכאלה…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2649:field_when:0:286
SUMMARY:Extensions of integral domains and quasi-valuations
DTSTART:2018-11-07T08:30:00
DTEND:2018-11-07T09:30:00
DSCRIPTION:Speaker: Dr. Shai Sarussi (Sami Shamoon College of Engineering)\n
Abstract:
Let S be an integral domain with field of fractions F, and let A be an F-algebra having an S-stable basis. We prove the existence of an S-subalgebra R of A lying over S whose localization with respect to S is A (we call such R an S-nice subalgebra of A). We also show that there is no such minimal S-nice subalgebra of A. Given a valuation v on F with a corresponding valuation domain Ov, and an Ov-stable basis of A over F, we prove the existence of a quasi-valuation on A extending v on…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2655:field_when:0:287
SUMMARY:Dimension of attractors for Iterated Function Systems of linear fractional transformations and the Diophantine property of matrix semigroups
DTSTART:2018-11-05T12:00:00
DTEND:2018-11-05T13:15:00
DSCRIPTION:Speaker: Dr. Yuki Takahashi, Bar-Ilan University\n
Abstract:
We consider Iterated Function Systems of linear fractional transformations, and show that the
Hausdorff dimension of the attractor is given by the Bowen's pressure formula, if the Iterated
Function Systems satisfy the exponential separation condition. We also show that almost every
finite collections of $GL_n( \mathbb{R} )$ matrices are Diophantine if the matrices have positive
entries. This is a joint work with Boris Solomyak.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2631:field_when:0:288
SUMMARY:Algebraic Ramsey-theoretic results with small monochromatic sets
DTSTART:2018-11-05T11:00:00
DTEND:2018-11-05T13:00:00
DSCRIPTION:Speaker: David Fernández-Bretón (KGRC)\n
Abstract:
We will explore some (recent and not so recent; some positive,
some negative) Ramsey-type results (each of which is due to some subset
of the set {Komj\'ath, Hindman, Leader, H.S. Lee, P. Russell, Shelah, D.
Soukup, Strauss, Rinot, Vidnyánszky, myself}) where abelian groups are
coloured, and one attempts to obtain monochromatic sets defined in terms
of the group structure. We will focus specifically on two families of
very recent results: the first one concerns colouring groups with…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2646:field_when:0:289
SUMMARY:Aldous' spectral gap conjecture for normal sets
DTSTART:2018-11-04T12:00:00
DTEND:2018-11-04T13:30:00
DSCRIPTION:Speaker: Doron Puder (Tel-Aviv University)\n
Abstract:
Aldous' spectral gap conjecture, proved in 2009 by Caputo, Liggett and Richthammer, states the following a priori very surprising fact: the spectral gap of a random walk on a finite graph is equal to the spectral gap of the interchange process on the same graph.
This seminal result has a very natural interpretation in Representation Theory, which leads to natural conjectural generalizations. In joint works with Gadi Kozma and Ori Parzanchevski we study some of these possible…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2654:field_when:0:290
SUMMARY:עקרון הסה - המציאות ואינסוף הצללים - מתמטיקה של גדולים הרצאה מס' 1
DTSTART:2018-10-31T13:00:00
DTEND:2018-10-31T14:00:00
DSCRIPTION:Speaker: פרופסור עוזי וישנה\n
Abstract:
"העקרון הלוקלי-גלובלי", הנקרא גם עקרון הסה, אחראי להתפתחויות רבות באריתמטיקה המודרנית. הרעיון פשוט: אם אפשר לפתור משוואה מעל השלמים, בוודאי אפשר לפתור אותה מודולו כל מספר ראשוני. אם כך, אם אפשר לפתור את המשוואה מודולו כל מספר ראשוני, אולי אפשר לפתור אותה גם בשלמים? נסקור כמה דוגמאות לעקרון הזה, שבהן המשוואה מוחלפת באובייקטים מתוחכמים יותר.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2635:field_when:0:291
SUMMARY:The shuffle algebra and Galois cohomology
DTSTART:2018-10-31T08:30:00
DTEND:2018-10-31T09:30:00
DSCRIPTION:Speaker: Prof. Ido Efrat (Ben-Gurion University)\n
Abstract:
Consider a prime number p and a free profinite group S on basis X.
We describe the quotients of S by the lower p-central filtration in terms of the shuffle algebra on X. This description is obtained by combining tools from the combinatorics of words with Galois cohomology methods.
In the context of absolute Galois groups, this machinery gives a new general perspective on recent arithmetical results on Massey products and other cohomological operations.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2642:field_when:0:292
SUMMARY:Grid peeling and the affine curve-shortening flow
DTSTART:2018-10-28T12:00:00
DTEND:2018-10-28T13:30:00
DSCRIPTION:Speaker: Gabriel Nivasch (Ariel University)\n
Abstract:
Experimentally, the convex-layer decomposition of subsets of the integer grid ("grid peeling") seems to behave at the limit like the affine curve-shortening flow. We offer some theoretical arguments to explain this phenomenon. In particular, we derive some rigorous results for the special case of peeling the quarter-infinite grid: We prove that, in this case, the number of grid points removed up to iteration n is Theta(n^(3/2)log n), and moreover, the boundary at iteration n is…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2645:field_when:0:293
SUMMARY:On the weak Muckenhoupt-Wheeden conjecture
DTSTART:2018-10-26T11:05:00
DTEND:2018-10-26T12:05:00
DSCRIPTION:Speaker: Prof. Andrei Lerner, Bar-Ilan University\n
Abstract:
We construct an example showing the sharpness of certain weighted weak type (1,1) bounds
for the Hilbert transform. This is joint work with Fedor Nazarov and Sheldy Ombrosi.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2625:field_when:0:294
SUMMARY:Generalized and degenerate Whittaker quotients and Fourier coefficients
DTSTART:2018-10-24T07:30:00
DTEND:2018-10-24T08:30:00
DSCRIPTION:Speaker: Prof. Dmitry Gourevitch (Weizmann Institute of Science)\n
Abstract:
The study of Whittaker models for representations of reductive groups over
local and global fields has become a central tool in representation theory and the theory of automorphic forms, though their Fourier coefficients. We will start by recalling the classical results on the existence and uniqueness of such models.
In order to encompass representations that do not have Whittaker models, one attaches a degenerate (or a generalized) Whittaker model WO, or a Fourier coefficient…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2656:field_when:0:295
SUMMARY:ראשוניים - כמה, איך ולמה, הרצאה מס' 1 בסדרת חור בהשכלה
DTSTART:2018-10-22T15:00:00
DTEND:2018-10-22T17:00:00
DSCRIPTION:Speaker: פרופ' עוזי וישנה\n
Abstract:
כולם יודעים מהם מספרים ראשוניים. כולם גם יודעים שאוקלידס הוכיח שיש אינסוף כאלה. בהרצאה נדבר על כמה מהמשפטים החשובים והפחות מוכרים על פיזור המספרים הראשוניים, ואפילו נוכיח אותם (בערך).
זוהי הרצאה ראשונה בסדרת "חור בהשכלה", שמטרתה להשלים נושאים חשובים שאינם מכוסים בקורסי התואר הראשון. תלמידי שנים ב' וג' מוזמנים במיוחד, אבל ההרצאה פתוחה לכל.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2641:field_when:0:296
SUMMARY:Spectral gap and sign changes of Gaussian stationary processes
DTSTART:2018-10-22T11:00:00
DTEND:2018-10-22T12:20:00
DSCRIPTION:Speaker: Dr. Naomi Feldheim, Bar-Ilan University\n
Abstract:
It is known that the Fourier transform of a measure which vanishes on [-a,a]
must have asymptotically at least a/pi zeroes per unit interval.
One way to quantify this further is using a probabilistic model:
Let f be a Gaussian stationary process on R whose spectral measure vanishes on [-a,a].
What is the probability that it has no zeroes on an interval of length L?
Our main result shows that this probability is at most e^{-c a^2 L^2}, where c>0 is an absolute constant.
This settles…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2630:field_when:0:297
SUMMARY:The representation theory of monoids associated to Coxeter groups and other combinatorial structures
DTSTART:2018-10-21T11:00:00
DTEND:2018-10-21T12:30:00
DSCRIPTION:Speaker: Stuart Margolis (Bar-Ilan University)\n
Abstract:
In the last twenty years it has been noticed that many combinatorial and geometric structures also have the structure of a monoid. These include real and complex hyperplane arrangements, Bruhat order of Coxeter groups, Schubert cells of linear algebraic groups and more.
The representation theory of these monoids can be used to study random walks and give other information about these structures. Connections between combinatorial and geometric structures and representations of finite…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2618:field_when:0:298
SUMMARY:Generating lamplighter groups with bireversible automata
DTSTART:2018-10-17T08:00:00
DTEND:2018-10-17T09:00:00
DSCRIPTION:Speaker: Dr. Rachel Skipper (Georg-August-Universität Göttingen)\n
Abstract:
We use the language of formal power series to construct finite state automata generating groups of the form A \wr Z, where A is the additive group of a finite commutative ring and Z is the integers. We then provide conditions on the ring and the power series which make automata bireversible.
This is a joint work with Benjamin Steinberg.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2617:field_when:0:299
SUMMARY:Common slots of bilinear and quadratic Pfister forms
DTSTART:2018-10-17T07:00:00
DTEND:2018-10-17T08:00:00
DSCRIPTION:Speaker: Dr. Adam Chapman (Tel-Hai Academic College)\n
Abstract:
We say that I^n(F) is m-linked if any m bilinear n-fold Pfsiter forms have a common (n-1)-fold factor. In a recent publication, Karim Becher pointed out that when F is a global field, I^n(F) is m-linked for every positive integer m, and raised the question of whether I^n(F) being 3-linked implies that it is m-linked for every positive integer m. In the special case of characteristic 2, this question can be phrased in two versions - one for bilinear forms and another for quadratic…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2665:field_when:0:300
SUMMARY:לוח ס"א ראשים ככלי לבחינת הפרשי שנים בין מופעים חוזרים של סימני השנה
DTSTART:2018-10-16T14:30:00
DTEND:2018-10-16T15:30:00
DSCRIPTION:Speaker: ד"ר ערן רביב, בר אילן\n
Abstract:
בהרצאות קודמות בבמה זאת ניתחנו והסברנו את חשיבותו של לוח ס"א ראשים (לוח טבלאי בן 61 שורות ו- 19 עמודות שנכתב בתקופת הראשונים בצרפת) ככלי לבדיקת שכיחויות של סימני השנה ושכיחות של סדרות של סימני השנה.
בהרצאה המוצעת נראה כיצד לוח זה משמש גם ככלי לבדיקת מרווחי השנים בין רצפים בלוח.
את הדיון התאורטי נבהיר בעזרת ניתוח הדוגמא שהעלה ידידנו מר אריה רוקח מקדומים, ולהלן דוגמתו:
השנים תשע"ט תש"פ סימנם בשז בשה בהתאמה, בעיון בלוח סימני השנים רואים שצירוף זה יופיע בעוד 71 שנים ואח"כ בדילוג של 98…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2629:field_when:0:301
SUMMARY:Trace reconstruction for the deletion channel
DTSTART:2018-10-15T11:00:00
DTEND:2018-10-15T12:10:00
DSCRIPTION:Speaker: Prof. Yuval Peres, Microsoft Research\n
Abstract:
In the trace reconstruction problem, an unknown string $x$ of $n$ bits is observed through
the deletion channel, which deletes each bit with some constant probability $q$, yielding
a contracted string. How many independent outputs (traces) of the deletion channel are needed
to reconstruct $x$ with high probability?
The best lower bound known is of order $n^{1.25}$. Until 2016, the best upper bound available
was exponential in the square root of $n$. With Fedor Nazarov, we improve the…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2616:field_when:0:302
SUMMARY:Trace reconstruction for the deletion channel
DTSTART:2018-10-15T11:00:00
DTEND:2018-10-15T12:00:00
DSCRIPTION:Speaker: Prof. Yuval Peres, Microsoft Research\n
Abstract:
In the trace reconstruction problem, an unknown string $x$ of $n$ bits is observed through the deletion channel, which deletes each bit with some constant probability $q$, yielding a contracted string. How many independent outputs (traces) of the deletion channel are needed to reconstruct $x$ with high probability?
The best lower bound known is of order $n^{1.25}$. Until 2016, the best upper bound available was exponential in the square root of $n$. With Fedor Nazarov, we…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2615:field_when:0:303
SUMMARY:Search games and Kakeya sets
DTSTART:2018-10-14T11:30:00
DTEND:2018-10-14T12:30:00
DSCRIPTION:Speaker: Yuval Peres (Microsoft Research)\n
Abstract:
I'll describe a search game with a surprising geometric connection. A hunter and a rabbit move on an n-vertex graph without seeing each other until they meet. At each step, the hunter moves to a neighboring vertex or stays in place, while the rabbit is free to jump to any node. Thus they are engaged in a zero sum game, where the payoff is the capture time. We show that an optimal rabbit strategy for the cycle yields a Kakeya set: a plane set of zero area that contains a unit segment…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2614:field_when:0:304
SUMMARY:Gravitational matching and allocation for uniform points on the sphere
DTSTART:2018-10-14T09:00:00
DTEND:2018-10-14T10:00:00
DSCRIPTION:Speaker: Prof. Yuval Peres, Microsoft Research\n
Abstract:
Given n uniform points on the surface of a two-dimensional sphere, how can we partition the sphere fairly among them? "Fairly" means that each region has the same area. It turns out that if the given points apply a two-dimensional gravity force to the rest of the sphere, then the basins of attraction for the resulting gradient flow yield such a partition—with exactly equal areas, no matter how the points are distributed. (See the cover of the AMS Notices at http://www.ams.org/…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2610:field_when:0:305
SUMMARY:Stable character theory and representation stability
DTSTART:2018-08-29T07:30:00
DTEND:2018-08-29T08:30:00
DSCRIPTION:Speaker: Nir Gadish (University of Chicago)\n
Abstract:
Various algebraic and topological situations give rise to compatible sequences of representations of different groups, such as the symmetric groups, with stable asymptotic behavior. Representation stability is a recent approach to studying such sequences, which has proved effective for extracting important invariants. Coming from this point of view, I will introduce the associated character theory, which explains many of the approach's strengths (in char 0). Central examples are…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2648:field_when:0:306
SUMMARY:המחלוקת המכונה ״בין סעדיה לבן מאיר״: שאלות ועניינים.
DTSTART:2018-06-26T14:00:00
DTEND:2018-06-26T15:30:00
DSCRIPTION:Speaker: פרופ' סשה שטרן, אוניברסיטה קולג׳ לונדון.\n
Abstract:
בהמשך להרצאתי של כ"ה בניסן תשע"ח על המחלוקת הידועה של שנת רל״ג לשטרות (המכונה ״בין סעדיה לבן מאיר״), אציג כאן שתי נקודות העולות ממחקרי החדש בנושא זה.
1. ידוע שלדעת בן מאיר גבולו של מולד זקן היה מאוחר מחצות היום, ובגלל זה קבע את מועדיו בתאריכים שונים מאלה שבבבל. רבו הניסיונות להסביר את מקור שיטתו (ויש להעדיף את הסברו של צ״ה יפה, כפי שטען לאחרונה הרב רחמים שר-שלום). ברם, כל ההסברים סמכו על הנחת יסוד שבן מאיר הוסיף 642 חלקים על גבול חצות היום, ואילו ברור למדי שבאמת לא הוסיף אלה 641…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2592:field_when:0:307
SUMMARY:Monomial braidings
DTSTART:2018-06-17T09:00:00
DTEND:2018-06-17T10:15:00
DSCRIPTION:Speaker: Jianrong Li (Weizmann Institute)\n
Abstract:
A braided vector space is a pair $(V, \Psi)$, where $V$ is a vector space
and $\Psi: V \otimes V \to V \otimes V$ is an invertible linear operator
such that $\Psi_1 \Psi_2 \Psi_1 = \Psi_2 \Psi_1 \Psi_2$. Given a braided
vector space $(V, \Psi)$, we constructed a family of braided vector spaces
$(V, \Psi^{(\epsilon)})$, where $\epsilon$ is a bitransitive function. Here a
bitransitive function is a function $\epsilon: [n] \times [n] \to \{1, -1\}$ such
that both of $\{(i,j…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2591:field_when:0:308
SUMMARY:Vologodsky and Coleman integration on curves with semi-stable reduction
DTSTART:2018-06-13T07:30:00
DTEND:2018-06-13T08:30:00
DSCRIPTION:Speaker: Prof. Amnon Besser (Ben-Gurion University)\n
Abstract:
Let X be a curve over a p-adic field K with semi-stable reduction and let ω be a meromorphic differential on X. There are two p-adic integrals one may associate to this data. One is the Vologodsky (abelian, Zarhin, Colmez) integral, which is a global function on the K-points of X defined up to a constant. The other is the collection of Coleman integrals on the subdomains reducing to the various components of the smooth locus. In this talk I will prove the following Theorem, joint with…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2604:field_when:0:309
SUMMARY:חיבורו של יעקב בר שמשון על הלוח העברי
DTSTART:2018-06-12T14:00:00
DTEND:2018-06-12T15:30:00
DSCRIPTION:Speaker: ד"ר אילנה ורטנברג, אוניברסיטת ברן\n
Abstract:
הרצאתי תתמקד בחיבורו הלוחי של יעקב בר שמשון, תלמידו של רש"י, שנכתב בצפון צרפת במאה ה-12, תקופה בה אנו עדים לפריחתה של סוגה זו בעברית.
החלקים ששרדו מן החיבור חושפים מסורות שונות של לוח השנה, בבליות וארץ ישראליות.
בניגוד למחברים ספרדים של אותה התקופה, כמו אברהם בר חייא ואברהם אבן עזרא, שהיו אנשי מדע מובהקים, אופן העברת הידע על הלוח העברי וארגונו על ידי בר שמשון אינם מדעיים כלל ועיקר.
תוכן החיבור מצביע, באופן לא מפתיע, על שליטה ספרותית במקרא ובספרות הרבנית אך בד בבד גם על השקפת עולם…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2581:field_when:0:310
SUMMARY:Asymptotic dilation of regular homeomorphisms
DTSTART:2018-06-11T11:00:00
DTEND:2018-06-11T12:45:00
DSCRIPTION:Speaker: Prof. Anatoly Golberg, Holon Institute of Technology\n
Abstract:
We study the asymptotic behavior of the ratio $|f(z)|/|z|$ as $z\to 0$ for homeomorphic mappings
differentiable almost everywhere in the unit disc with non-degenerated Jacobian. The main tools
involve the length-area functionals and angular dilatations depending on some real number $p.$
The results are applied to homeomorphic solutions of a nonlinear Beltrami equation. The estimates
are illustrated by examples.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2589:field_when:0:311
SUMMARY:Chang's Conjecture, club-increasing sequences, and P_max forcing, Part 2
DTSTART:2018-06-11T10:00:00
DTEND:2018-06-11T12:10:00
DSCRIPTION:Speaker: Chris Lambie-Hanson (BIU) \n
Abstract:
In this talk, we will continue the investigation of questions involving Chang's Conjectures and the existence of certain club-increasing sequences. We begin by finishing our introduction of P_max forcing and sketching proofs of the facts that comprise the basic analysis thereof. We then present Larson's P_max variation that can be used to force the existence of a club-increasing sequence of length omega_2 in omega^omega over a model of AD^+ + V=L(A,R).
END:VEVENT
BEGIN:VEVENT
UID:calendar:2585:field_when:0:312
SUMMARY:Extremal subsets of the boolean cube with respect to projections
DTSTART:2018-06-10T11:00:00
DTEND:2018-06-10T12:30:00
DSCRIPTION:Speaker: Noam Solomon (Harvard University)\n
Abstract:
In this talk, we will present an asymptotically tight bound on the largest number of distinct projections onto \alpha n coordinates guaranteed in any family of n^r binary vectors of length n, where 0 < \alpha \le 1 and r = n^{o(1)}, thus closing a gap open since a work of Bollobas and Radcliffe from 1995. For the proof, we establish a “sparse” version of a classical result, the Kruskal-Katona Theorem, where we give a stronger guarantee when the hypergraph does not induce dense…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2588:field_when:0:313
SUMMARY:Counting holomorphic disks using bounding chains
DTSTART:2018-06-10T09:15:00
DTEND:2018-06-10T10:15:00
DSCRIPTION:Speaker: Sara Tukachinsky, Princeton University\n
Abstract:
In 2003, Welschinger defined invariants of real symplectic
manifolds of complex dimensions 2 and 3, which are related to counts
of pseudo-holomorphic disks with boundary and interior point
constraints (Solomon, 2006). The problem of extending the definition
to higher dimensions remained open until recently (Georgieva, 2013,
and Solomon-Tukachinsky, 2016-17).
In the talk I will give some background on the problem, and describe
a generalization of Welschinger's invariants to higher…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2587:field_when:0:314
SUMMARY:Interlocking Structures
DTSTART:2018-06-10T08:00:00
DTEND:2018-06-10T09:00:00
DSCRIPTION:Speaker: Alexei Kanel-Belov, Bar-Ilan University\n
Abstract:
Consider a set of convex figures in R^2. It can be proven
that one of these figures can be moved out of the set by translation
without disturbing the others. Therefore, any set of planar figures
can be disassembled by moving all figures one by one. However,
attempts to generalize it to R^3 have been unsuccessful and finally,
quite unexpectedly, interlocking structures of convex bodies were
found. These structures can be used in engineering. In a small grain
there is no room for cracks…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2584:field_when:0:315
SUMMARY:The combinatorics of odd and chiral partitions
DTSTART:2018-06-03T11:00:00
DTEND:2018-06-03T12:30:00
DSCRIPTION:Speaker: Arvind Ayyer (Indian Institute of Science)\n
Abstract:
We say that a partition is odd if its dimension (computed by the hook-length formula) is odd. It turns out that the number a(n) of odd partitions of a positive integer is always a power of 2. This was proven independently by Macdonald and McKay. We will show that the subposet of the Young lattice consisting of odd partitions is a binary tree, and give an explicit recursive characterisation of this tree.
We say that a partition is chiral if the associated irreducible representation…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2580:field_when:0:316
SUMMARY:Complements of closed geodesics
DTSTART:2018-06-03T09:00:00
DTEND:2018-06-03T10:00:00
DSCRIPTION:Speaker: Tali Pinsky, Technion\n
Abstract:
I will describe some nice connections between closed
geodesics on surfaces, knot theory, continued fractions and hyperbolic
three-manifolds. Using a certain gadget called a "template" for the
modular surface, found by Ghys, it is possible to obtain an upper
bound for the volume of a geodesic (or its complement in the unit
tangent bundle) in terms of its length. This is joint work with Maxime
Bergeron and Lior Silberman.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2574:field_when:0:317
SUMMARY:Invariable generation
DTSTART:2018-05-30T08:00:00
DTEND:2018-05-30T09:00:00
DSCRIPTION:Speaker: Gil Goffer (Weizmann Institute of Science)\n
Abstract:
A group is said to be invariably generated (IG) by a set S if any conjugation of elements of S still generates G, and topologically invariably generated (TIG) by S if every such conjugation generates G topologically.
I will give a short review of this notion and present new results from joint work with Gennady Noskov.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2575:field_when:0:318
SUMMARY:Octonion algebras via G_2-torsors and triality
DTSTART:2018-05-30T07:00:00
DTEND:2018-05-30T08:00:00
DSCRIPTION:Speaker: Dr. Seidon Alsaody (Institut Camille Jordan, Université Lyon 1)\n
Abstract:
An octonion algebra is a unital, non-associative algebra endowed with a non-degenerate, multiplicative quadratic form. Such algebras are crucial in the construction of exceptional groups. Over fields, it is known that the quadratic form determines the algebra structure completely. Remarkably, this is not true over commutative rings in general, as was shown by P. Gille in 2014 using cohomological arguments.
I will talk about a recent joint work with Gille, where we give an explicit…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2573:field_when:0:319
SUMMARY:Chang's Conjecture, club-increasing sequences, and P_max forcing, part 1
DTSTART:2018-05-28T10:00:00
DTEND:2018-05-28T12:00:00
DSCRIPTION:Speaker: Chris Lambie-Hanson (BIU)\n
Abstract:
The consistency of the Chang's Conjecture (CC) variant (aleph_{omega + 1}, aleph_omega) ->> (aleph_2, aleph_1) is a major open question. A combinatorial consequence of this instance of CC is the existence of a certain strongly increasing sequence, of length aleph_2, of functions from omega to some fixed ordinal below omega_2 (we are calling such a sequence a club-increasing sequence). In response to a question from the speaker, Paul Larson proved the consistency of the existence…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2583:field_when:0:320
SUMMARY:Card shuffling, quantum mechanics and representation theory
DTSTART:2018-05-27T11:30:00
DTEND:2018-05-27T13:00:00
DSCRIPTION:Speaker: Gady Kozma (Weizmann Institute)\n
Abstract:
It has been known since work of Feynman in the 50s that the behaviour of quantum systems is related to cycles of random permutations,
and for some systems this can be made a precise mathematical claim. Similar problems appear in the, mostly recreational, field of card shuffling.
All these problems can be attacked by representation theory, but algebra alone is not enough, as the functions involved are not class functions.
This creates an exciting analytic-algebraic nexus which…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2562:field_when:0:321
SUMMARY:On some applications of group representation theory to algebraic problems related to the congruence principle for equivariant maps
DTSTART:2018-05-23T07:30:00
DTEND:2018-05-23T08:30:00
DSCRIPTION:Speaker: Prof. Mikhail Muzychuk (Ben-Gurion University)\n
Abstract:
Given a finite group G and two unitary G-representations V and W, possible restrictions on Brouwer degrees of equivariant maps between the representation spheres S(V) and S(W) are usually expressed in terms of congruences modulo the greatest common divisor of lengths of orbits in S(V) (denoted α(V)). Effective application of these congruences is limited by answers to the following questions:
(i) Under which conditions is α(V)>1?
(ii) Does there exist an equivariant map whose…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2558:field_when:0:322
SUMMARY:Supersingular representations of unramified U(2,1)
DTSTART:2018-05-16T07:30:00
DTEND:2018-05-16T08:30:00
DSCRIPTION:Speaker: Dr. Peng Xu (Hebrew University of Jerusalem)\n
Abstract:
The recent work of Abe--Henniart--Herzig--Vigneras gives a classification of irreducible admissible mod-p representations of a p-adic reductive group in terms of supersingular/supercuspidal representations. However, supersingular representations remain mysterious largely, and in general we know them very little. So far, there are only classifications of them for the group GL_2 (Q_p) and a few other closely related cases.
In this talk, we will present some work on the unramified…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2560:field_when:0:323
SUMMARY:On cycles in asymmetric models of circular gene networks
DTSTART:2018-05-14T12:05:00
DTEND:2018-05-14T13:00:00
DSCRIPTION:Speaker: Prof. Vladimir Golubyatnikov, Sobolev institute of mathematics, Novosibirsk, Russia\n
Abstract:
We study geometry and combinatorial structures of phase portrait of some nonlinear
kinetic dynamical systems as models of circular gene networks in order to find conditions
of existence of cycles of these systems. Some sufficient conditions of existence of their
stable cycles are obtained as well.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2559:field_when:0:324
SUMMARY:Spectrality of Product Domains
DTSTART:2018-05-14T11:00:00
DTEND:2018-05-14T12:00:00
DSCRIPTION:Speaker: Rachel Greenfeld, Bar-Ilan University\n
Abstract:
A set $\Omega$ in $R^d$ is called spectral if the space $L^2(\Omega)$ admits an orthogonal basis consisting of exponential
functions. Which sets $\Omega$ are spectral? This question is known as "Fuglede's spectral set problem".
In the talk we will be focusing on the case of product domains, namely, when $\Omega = AxB$.
In this case, it is conjectured that $\Omega$ is spectral if and only if the factors A and B are both spectral.
We will discuss some new results, joint with Nir Lev,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2556:field_when:0:325
SUMMARY:Cardinal characteristics of omega_1
DTSTART:2018-05-14T10:00:00
DTEND:2018-05-14T12:00:00
DSCRIPTION:Speaker: William Chen (BGU)\n
Abstract:
We introduce a new cardinal invariant related to stick, prove some basic facts about it, and ask some open questions. Joint work with Geoff Galgon.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2554:field_when:0:326
SUMMARY:The Amit-Vishne condition for semi-rationality of groups
DTSTART:2018-05-09T07:30:00
DTEND:2018-05-09T08:30:00
DSCRIPTION:Speaker: Tzoor Plotnikov (Hebrew University of Jerusalem)\n
Abstract:
A finite group is called semi-rational if the distribution induced on it by any word map is a virtual character. Amit and Vishne give a sufficient condition for a group to be semi-rational, and ask whether it is also necessary. We answer this in the negative, by exhibiting two new criteria for semi-rationality, each giving rise to an infinite family of semi-rational groups which do not satisfy the Amit-Vishne condition. On the other hand, we use recent work of Lubotzky to show that…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2555:field_when:0:327
SUMMARY:Methods of Nonassociative Algebras in Differential Equations
DTSTART:2018-05-07T11:00:00
DTEND:2018-05-07T12:45:00
DSCRIPTION:Speaker: Prof. Ya. Krasnov, Bar-Ilan University\n
Abstract:
Many well-known (classes of) differential equations may be viewed as an equation in a certain
commutative nonassociative algebra. We develop further the principal idea of L. Markus for deriving
algebraic properties of solutions to ODEs and PDEs directly from the equations defining them.
Our main purpose is a) to show how the algebraic formalism can be applied with great success to a
remarkably elegant description of the geometry of curves being solutions to homogeneous polynomial…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2582:field_when:0:328
SUMMARY:Open problems related to adjacency eigenvalues and zeta functions
DTSTART:2018-05-06T11:00:00
DTEND:2018-05-06T12:15:00
DSCRIPTION:Speaker: Joel Friedman (University of British Columbia, Canada)\n
Abstract:
We express some open problems in graph theory in terms of Ihara graph zeta
functions, or, equivalently, non-backtracking matrices of graphs. We focus
on "expanders" and random regular graphs, but touch on some seemingly
unrelated problems encoded in zeta functions.
We suggest that zeta functions of sheaves on graphs may have relevance to
complexity theory and to questions of Stark and Terras regarding whether
coverings of a fixed graph can ramify like number field extensions.
This…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2553:field_when:0:329
SUMMARY:On semi-conjugate rational functions
DTSTART:2018-05-06T09:00:00
DTEND:2018-05-06T10:00:00
DSCRIPTION:Speaker: Fedor Pakovich, Ben-Gurion University\n
Abstract:
Let $A$ and $B$ be rational functions on the Riemann sphere. The function $B$ is said to be semi-conjugate to the function $A$ if
there exists a non-constant rational function $X$ such that
$$
A\circ X=X\circ B. (*)
$$
The semi-conjugacy condition generalises both the classical conjugacy relation and the commutativity condition. In the talk we present a description of solutions of functional equation (*) in terms of orbifolds of non-negative Euler characteristic on the Riemann…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2550:field_when:0:330
SUMMARY:Stability, invariant random subgroups, and property testing
DTSTART:2018-05-02T07:30:00
DTEND:2018-05-02T08:30:00
DSCRIPTION:Speaker: Oren Becker (Hebrew University of Jerusalem)\n
Abstract:
Given two permutations A and B which "almost" commute, are they "close" to permutations A' and B' which really commute? Arzhantseva and Paunescu (2015) formalized this question and answered affirmatively. This can be viewed as a property of the equation XY=YX, and turns out to be equivalent to the following property of the group Z^2 = < X,Y | XY=YX >: Every "almost action" of Z^2 on a finite set is close to a genuine action of Z^2. This leads to the notion of stable groups.…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2578:field_when:0:331
SUMMARY:לוח השנה ותולדותיו: ההבדל בין הגישה המחקרית לבין הגישה המסורתית.
DTSTART:2018-05-01T14:15:00
DTEND:2018-05-24T15:30:00
DSCRIPTION:Speaker: הרב מאיר שמואלביץ, עורך באנציקלופדיה התלמודית\n
Abstract:
להרצאה המצולמת
END:VEVENT
BEGIN:VEVENT
UID:calendar:2552:field_when:0:332
SUMMARY:Holomorphic extensions of trace formulas
DTSTART:2018-04-30T11:00:00
DTEND:2018-04-30T12:35:00
DSCRIPTION:Speaker: Dr. Serge Itshak Lukasuewicz, Bar-Ilan University\n
Abstract:
The Chazarain-Poisson summation formula for Riemannian manifolds (which generalizes the Poisson Summation formula)
computes the distribution trace. In the case of Riemannian surfaces with constant (sectional) curvature, we study
the holomorphic extension of the shifted trace. We have three generic cases according to the sign of the curvature:
the sphere, the torus and the compact hyperbolic surfaces of negative constant curvature. We use the shifted
Laplacian in order to be able to…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2546:field_when:0:333
SUMMARY:Uniqueness triples from the diamond axiom
DTSTART:2018-04-30T10:00:00
DTEND:2018-04-30T12:00:00
DSCRIPTION:Speaker: Ari Brodsky (Ariel University)\n
Abstract:
We work with a $\lambda$-frame, which is an abstract elementary class endowed with a collection of basic types and a non-forking relation satisfying certain natural properties with respect to models of cardinality $\lambda$.
We will show that assuming the diamond axiom, any basic type admits a non-forking extension that has a uniqueness triple.
Prior results of Shelah in this direction required either some form of diamond at two consecutive cardinals, or a constraint on the number of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2551:field_when:0:334
SUMMARY:Exotic cluster structures on SL_n
DTSTART:2018-04-29T11:00:00
DTEND:2018-04-29T13:00:00
DSCRIPTION:Speaker: Alek Vainshtein (University of Haifa)\n
Abstract:
Back in 2005, Berenstein, Fomin and Zelevinsky discovered a cluster
structure in the ring of regular functions on a double Bruhat cell in a
semisimple Lie group, in particular, SL_n. This structure can be easily
extended to the whole group. The compatible Poisson bracket is given by
the standard r-matrix Poisson-Lie structure on SL_n. The latter is a
particular case of Poisson-Lie structures corresponding to
quasi-triangular Lie bialgebras. Such structures where classified in 1982
by…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2549:field_when:0:335
SUMMARY:Angles of Gaussian primes
DTSTART:2018-04-29T09:00:00
DTEND:2018-04-29T10:00:00
DSCRIPTION:Speaker: Zeev Rudnick, Tel-Aviv University\n
Abstract:
Fermat showed that every prime p = 1 mod 4 is a sum of two squares: $p = a^2 + b^2$, and hence such a prime gives rise to an angle whose tangent is the ratio $b/a$. Do these angles exhibit order or randomness? I will discuss the statistics of these angles and present a conjecture, motivated by a random matrix model and by function field considerations.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2542:field_when:0:336
SUMMARY:The Herzog-Schönheim conjecture for finitely generated groups
DTSTART:2018-04-25T07:30:00
DTEND:2018-04-25T08:30:00
DSCRIPTION:Speaker: Dr. Fabienne Chouraqui (Haifa University)\n
Abstract:
Let G be a group and H_1,...,H_s be subgroups of G of indices d_1,...,d_s respectively. In 1974, M. Herzog and J. Schönheim conjectured that if \{H_i a_i\}_{i=1}^{i=s} is a coset partition of G, then d_1,..,d_s cannot be distinct. We consider the Herzog-Schönheim conjecture for free groups of finite rank and develop a new combinatorial approach, using covering spaces. We give some sufficient conditions on the coset partition that ensure the conjecture is satisfied. Furthermore,…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2548:field_when:0:337
SUMMARY:L^p estimates for graph eigenfunctions
DTSTART:2018-04-22T09:00:00
DTEND:2018-04-22T10:00:00
DSCRIPTION:Speaker: Shimon Brooks, Bar-Ilan University\n
Abstract:
Do “chaotic” waves spread out randomly, or can they
concentrate near a point? In the 70s, Berard gave non-trivial bounds
for the sup-norm of a Laplace eigenfunction on a manifold of negative
sectional curvature; though far from the conjectured bounds for
surfaces of negative curvature, and those predicted by the random-wave
model, the bound has not been improved on since. Recently, Hassel and
Tacy extended Berard’s result to L^p norms, for all p>6.
In this talk we will focus on…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2545:field_when:0:338
SUMMARY:Smooth parametrizations (of semi-algebraic, o-minimal, … sets), and their applications in Dynamics, Analysis, and Diophantine geometry (and, maybe, in Complex Hyperbolic Geometry)
DTSTART:2018-04-16T11:00:00
DTEND:2018-04-16T12:15:00
DSCRIPTION:Speaker: Prof. Yosef Yomdin, Weizmann Institute\n
Abstract:
Smooth parametrization consists in a subdivision of a mathematical object under consideration into simple pieces,
and then parametric representation of each piece, while keeping control of high order derivatives. Main examples
for this talk are C^k or analytic parametrizations of semi-algebraic and o-minimal sets.
We provide an overview of some results, open and recently solved problems on smooth parametrizations, and their
applications in several apparently rather separated domains:…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2544:field_when:0:339
SUMMARY:Symplectic geometry and C^0 rigidity
DTSTART:2018-04-15T09:00:00
DTEND:2018-04-15T10:00:00
DSCRIPTION:Speaker: Lev Buhovski, Tel-Aviv University\n
Abstract:
I will talk about the Eliashberg-Gromov theorem on C^0 rigidity of symplectic diffeomorphisms, and its extensions obtained recently in the framework of C^0 symplectic geometry.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2541:field_when:0:340
SUMMARY:Convolutions of algebraic morphisms and applications
DTSTART:2018-04-11T07:30:00
DTEND:2018-04-11T08:30:00
DSCRIPTION:Speaker: Yotam Hendel (Weizmann Institute of Science)\n
Abstract:
In analysis, the convolution of two functions results in a smoother, better behaved function. A natural question is then whether this phenomenon has an analogue in the setting of algebraic geometry.
Let f,g be two morphisms from algebraic varieties X,Y to an algebraic group G. We define their convolution to be a morphism f*g from X x Y to G by first applying each morphism to its respective coordinate and then multiplying using the group structure of G.
In this talk, we will…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2568:field_when:0:341
SUMMARY:המחלוקת המכונה ״בין סעדיה לבן מאיר״: מהדורה חדשה והערכה מחודשת
DTSTART:2018-04-10T14:30:00
DTEND:2018-04-10T15:30:00
DSCRIPTION:Speaker: פרופ' סשה שטרן, אוניברסיטה קולג׳, לונדון\n
Abstract:
בהרצאה זו אציג את מחקרי בנושא המחלוקת בין ראש הגולה וראשי ישיבות בבל לבין בן-מאיר, ראש ישיבת ארץ ישראל, בענין קביעת הלוח של שנת רל״ג למנין השטרות (921-922 לס׳).
חלק ניכר מעבודתי היא מהדורה חדשה של כל קטעי הגניזה. המהדורות הקודמות שסמכו עליהם בורנשטיין והחוקרים אחריו היו שגויות ביותר. חזרתי לקטעי הגניזה במטרה לא רק לההדיר את הטקסט אלא גם לשחזר כנכון את כתבי היד, ועל ידי זה להבין איך ולמה נמסרו ונשמרו כתבי בעלי המחלוקת במאות שלאחר המחלוקת. מהדורתי הביאה אותי להערכה מחודשת של פרשה…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2543:field_when:0:342
SUMMARY:An $L^2$ identity and pinned distance problem
DTSTART:2018-04-09T11:00:00
DTEND:2018-04-09T12:35:00
DSCRIPTION:Speaker: Dr. Bochen Liu, Bar-Ilan University\n
Abstract:
Given a measure on a subset of Euclidean spaces. The $L^2$ spherical averages of the Fourier transform of this measure was originally used to attack Falconer distance conjecture, via Mattila’s integral. In this talk, we will consider pinned distance problem, a stronger version of Falconer distance problem, and show that spherical averages imply the same dimensional threshold on both problems. In particular, with the best known spherical averaging estimates, we improve a result of…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2536:field_when:0:343
SUMMARY:Filter compactness and squares
DTSTART:2018-04-09T10:00:00
DTEND:2018-04-09T12:00:00
DSCRIPTION:Speaker: Yair Hayut (TAU) \n
Abstract:
Strongly compact cardinals are characterized by the property that any $\kappa$-complete filter can be extended to a $\kappa$-complete ultrafilter. When restricting the cardinality of the underlying set, we obtain a nontrivial hierarchy. For example, when requiring the extension property to hold only for filters on $\kappa$, we obtain Gitik's $\kappa$-compact cardinals, which are known to be consistently weaker than $\kappa$ being $\kappa^+$-strongly compact.
In this talk I will focus…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2537:field_when:0:344
SUMMARY:The Junta Method for Hypergraphs
DTSTART:2018-04-08T09:00:00
DTEND:2018-04-08T10:00:00
DSCRIPTION:Speaker: Nathan Keller, Bar-Ilan University\n
Abstract:
Numerous problems in extremal hypergraph theory ask to determine the maximal size of a k-uniform hypergraph on n vertices that does not contain an 'enlarged' copy H^+ of a fixed hypergraph H. These include well-known problems such as the Erdos-Sos 'forbidding one intersection' problem and the Frankl-Furedi 'special simplex' problem.
In this talk we present a general approach to such problems, using a 'junta approximation method' that originates from analysis of Boolean…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2528:field_when:0:345
SUMMARY:Finite subgroups of special linear groups, with arithmetic applications
DTSTART:2018-03-21T08:30:00
DTEND:2018-03-21T09:30:00
DSCRIPTION:Speaker: Prof. Yuval Flicker (Ariel University and Ohio State University)\n
Abstract:
The classification of finite subgroups of SL(2,C) has many applications from automorphy of Galois representations to singularity theory and to string theory. I shall describe the classification of finite subgroups of SL(3,C), and a few applications to questions of rationality and linearly reductive groups.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2531:field_when:0:346
SUMMARY:Differential and Difference Inclusions and the Filippov Theorem
DTSTART:2018-03-19T12:00:00
DTEND:2018-03-19T13:40:00
DSCRIPTION:Speaker: Prof. Elza Farkhi, Tel-Aviv University\n
Abstract:
The talk surveys joint works with T. Donchev and more recent ones with R. Baier.
We discuss some (continuous and discrete) versions of the celebrated Filippov
theorem on approximate solutions of differential (and difference) equations and
inclusions that extend classical stability results for differential equations
with continuous and discontinuous right-hand sides. We present some applications
related to numerical solution of differential equations and inclusions.
END:VEVENT
BEGIN:VEVENT
UID:calendar:2530:field_when:0:347
SUMMARY:Knaster and friends
DTSTART:2018-03-19T11:00:00
DTEND:2018-03-19T13:00:00
DSCRIPTION:Speaker: Assaf Rinot\n
Abstract:
In the 1970's, consistent examples of k-cc posets whose square is not k-cc were constructed by Laver, Fleissner, and Galvin. Later on, ZFC examples were constructed by Todorcevic, Shelah and others. The hardest case, being k=w2, was resolved by Shelah in 1997.
In this work, we obtain analogous results for k-Knaster posets. Among others, for any successor cardinal k, we produce a ZFC example of a k-Knaster poset whose w-power is not k-cc.
To do so, we introduce a new coloring principle…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2532:field_when:0:348
SUMMARY:Modelling processes on the Z^d-lattice
DTSTART:2018-03-18T10:00:00
DTEND:2018-03-18T11:00:00
DSCRIPTION:Speaker: Nishant Chandgotia, Tel-Aviv University\n
Abstract:
Suppose that we are given a stationary stochastic process
{X_n}_{n\in Z}. Can we model it by another stationary stochastic
process {Y_n}_{n\in Z} where Y_n can take only two values? In 1971,
Krieger answered with an affirmative under certain natural
assumptions. It is now well-known that the analogous result holds true
for modelling stationary random fields {X_n}_{n\in Z^d} as well. What
if we now constrain the stationary stochastic process {Y_n}_{n\in Z^d}
to take only three…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2527:field_when:0:349
SUMMARY:A non-abelian analogue of Herbrand-Ribet
DTSTART:2018-03-14T08:30:00
DTEND:2018-03-14T09:30:00
DSCRIPTION:Speaker: Dr. Devika Sharma (Weizmann Institute of Science)\n
Abstract:
Following the natural instinct that when a group operates on a number field k, every term in the class number formula factorizes “compatibly” according to the representation theory (both complex and modular) of the group, we are led to some questions about the p-part of the class group of k. The case when k is the cyclotomic extension Q(\mu_p) is the famous Herbrand-Ribet theorem. We generalize these questions to k = Q(E[p]), where E[p] is the group of p-torsion points on an…
END:VEVENT
BEGIN:VEVENT
UID:calendar:2525:field_when:0:350
SUMMARY:The proper way to color a grid
DTSTART:2018-03-11T10:00:00
DTEND:2018-03-11T11:00:00
DSCRIPTION:Speaker: Prof. Ron Peled, Tel-Aviv University\n
Abstract:
We consider the task of coloring the vertices of a large discrete box in the integer lattice Z^d with q colors so that no two adjacent vertices are colored the same. In how many ways can this be done? How does a typical coloring look like? What is the proportion of proper colorings in which two opposite corners of the box receive the same color? Is it about one in q?
We discuss these questions and the way their answers depend on the dimension d and the number of colors q, presenting…
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