Fall 2019

All the talks are 4:00pm-5:00pm in Room 5417 at the CUNY Graduate Center.

Wine and cheese are served afterwards in the math lounge on the 4th floor.

*September 13,  Heejoung Kim (University of Illinois at Urbana-Champaign)

TitleAlgorithms detecting stability and Morseness for finitely generated groups


For a word-hyperbolic group G, the notion of quasiconvexity is independent on the choice of a generating set and a quasiconvex subgroup of G is quasi-isometrically embedded in G. In 1994 Kapovich provided a partial algorithm which, on input a finite set S of G, halts if S generates a quasiconvex subgroup of G and runs forever otherwise.

However, beyond word-hyperbolic groups, the notion of quasiconveixty is not as useful.

For a finitely generated group, there are two recent generalizations of the notion of a quasiconvex subgroup of a word-hyperbolic group, a ``stable'' subgroup and a ``Morse'' subgroup.

In this talk, we will discuss various detection and decidability algorithms for stability and Morseness of a finitely generated subgroup of mapping class groups, right-angled Artin groups, toral relatively hyperbolic groups.

*September 20,  Susan Hermiller (University of Nebraska)

TitleAlgorithms for groups of PL homeomorphisms


The group PL_+(I) of orientation-preserving piecewise-linear homeomorphisms of the unit interval includes many important subgroups, most notably R. Thompson's group F. We study dynamical properties of the homeomorphisms in `computable' subgroups of PL_+(I) (including F) to give an algorithm which determines whether or not any given finite subset of such a computable group generates a solvable group. We give an application of this to solving the subgroup membership problem for a large family of finitely generated solvable subgroups of finitely generated groups of PL homeomorphisms. This is joint work with Collin Bleak and Tara Brough.

*September 27,   

*October 4,  Ariane Masuda (New York City College of Technology)



*October 18, Denis Osin (Vanderbilt  University)

*October 25, Piotr Nowak (McGill University)

The seminar meets Friday 4:00-5:00 p.m. at the Graduate Center of the City University of New York (Room 5417).  
The current organizers are:  

If you would like to give a talk, or have a suggestion for a seminar speaker, please e-mail one of the organizers. If you want to be added to/removed from the NYGT Seminar mailing list, please e-mail Ilya Kapovich at ikapovitch@gmail.com.
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