Nonpositive immersions and counting cycles

Wed, 25/05/2016 - 10:30
Speaker: 
Seminar: 
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Abstract: 

The "nonpositive immersion" property is a condition on a 2-complex X

 that generalizes being a surface. When X has this property,  its

 fundamental group appears to have has some very nice properties which

 I will discuss. I will spend the remainder of the talk outlining a

 proof that the nonpositive immersion property holds for a 2-complex

 obtained by attaching a single 2-cell to a graph. This was proven

 recently with Joseph Helfer and also independently by Lars Louder and Henry Wilton.