Geometry/Topology Seminar
Spring 2018
Thursdays (and sometimes Tuesdays) 34pm, in
Ryerson 358

 Thursday October 11 at 34pm in Ry 358
 Rita Gitik, University of Michigan

On Tame Subgroups of Finitely Presented Groups

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.

 Thursday October 18 at 34pm in Ry 358
 Daniel Ramras, IUPUI
 Homological stability for spaces of representations

Abstract: I will discuss recent work with Mentor
Stafa on homological stability for various spaces built from
commuting elements in Lie groups. These results depend on
rational models for these spaces due to T. Baird, and
utilize J. Wilson's theory of FI_{W}modules. A key
aspect of this work is the relationship between stability in
ordinary and in equivariant (co)homology. Time permitting,
I'll also discuss what is known regarding stability for
character varieties of free groups and surface groups.

 Thursday October 25 at 34pm in Ry 358
 Daniel Studenmund, Notre Dame
 Commensurability growth of nilpotent groups

Abstract: A classical area of study in geometric
group theory is subgroup growth, which counts the number of
subgroups of a given group Gamma as a function their index.
We will study a richer function, the commensurability
growth, associated to a subgroup Gamma in an ambient group
G. The main result of this talk concerns the case that Gamma
is an arithmetic subgroup of a unipotent group G, starting
with the simplest example of the integers in the real line.
This is joint work with Khalid BouRabee.

 Thursday November 01 at 34pm in Ry 358
 Yulan Qing, University of Toronto
 Loops with Large Twist Get Short Along Quasigeodesics in Out(Fn)

Abstract: We study the behaviour of quasigeodesics
in Out(Fn) equipped with word metric. Given an element
\phi of Out(Fn), there are several natural paths
connecting the origin to \phi in Out(Fn). We show
that these paths are, in general, not quasigeodesics in
Out(Fn). In fact, we clear up the current misunderstanding
about distance estimating in Out(Fn) by showing that there
exists points in Out(Fn) where all quasigeodesics between
them backtracks in all of the current Out(Fn) complexes .

 Thursday November 08 at 34pm in Ry 358
 Kevin Schreve, University of Chicago
 TBA

Abstract: TBA

 Thursday November 15 at 34pm in Ry 358
 Trevor Hyde, University of Michigan
 TBA

Abstract: TBA

 Thursday November 29 at 34pm in Ry 358
 Kasia Jankiewicz, University of Chicago
 TBA

Abstract: TBA
Due to the high number of requests, we are no longer accepting speakers via selfinvitations.
For questions, contact