Seminars and Colloquia by Series

Joint GT-UGA Seminar at GT - Fibered, homotopy-ribbon disk-knots by Jeff Meier

Series
Geometry Topology Seminar
Time
Monday, October 2, 2017 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Jeff Meier – UGA
I'll introduce you to one of my favorite knotted objects: fibered, homotopy-ribbon disk-knots. After giving a thorough overview of these objects, I'll discuss joint work with Kyle Larson that brings some new techniques to bear on their study. Then, I'll present new work with Alex Zupan that introduces connections with Dehn surgery and trisections. I'll finish by presenting a classification result for fibered, homotopy-ribbon disk-knots bounded by square knots.

Joint GT-UGA Seminar at GT - Homology Cobordism of Seifert Spaces

Series
Geometry Topology Seminar
Time
Monday, October 2, 2017 - 13:55 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Matt Stoffregen – MIT
We use Manolescu's Pin(2)-equivariant Floer homology to study homology cobordisms among Seifert spaces. In particular, we will show that the subgroup of the homology cobordism group generated by Seifert spaces admits a \mathbb{Z}^\infty summand. This is joint work with Irving Dai.

On boundaries of relatively hyperbolic right-angled Coxeter groups

Series
Geometry Topology Seminar
Time
Monday, September 25, 2017 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Hung Tran – Georgia
We give "visual descriptions" of cut points and non-parabolic cut pairs in the Bowditch boundary of a relatively hyperbolic right-angled Coxeter group. We also prove necessary and sufficient conditions for a relatively hyperbolic right-angled Coxeter group whose defining graph has a planar flag complex with minimal peripheral structure to have the Sierpinski carpet or the 2-sphere as its Bowditch boundary. We apply these results to the problem of quasi-isometry classification of right-angled Coxeter groups. Additionally, we study right-angled Coxeter groups with isolated flats whose $\CAT(0)$ boundaries are Menger curve. This is a joint work with Matthew Haulmark and Hoang Thanh Nguyen.

Taut branched surfaces from veering triangulations

Series
Geometry Topology Seminar
Time
Monday, September 18, 2017 - 13:55 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Michael Landry – Yale –
Let M be a closed hyperbolic 3-manifold with a fibered face \sigma of the unit ball of the Thurston norm on H_2(M). If M satisfies a certain condition related to Agol’s veering triangulations, we construct a taut branched surface in M spanning \sigma. This partially answers a 1986 question of Oertel, and extends an earlier partial answer due to Mosher. I will not assume knowledge of the Thurston norm, branched surfaces, or veering triangulations.

Around a big mapping class group

Series
Geometry Topology Seminar
Time
Tuesday, August 22, 2017 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Juliette Bavard – University of Chicago
The mapping class group of the plane minus a Cantor set naturally appears in many dynamical contexts, including group actions on surfaces, the study of groups of homeomorphisms on a Cantor set, and complex dynamics. In this talk, I will present the 'ray graph', which is a Gromov-hyperbolic graph on which this big mapping class group acts by isometries (it is an equivalent of the curve graph for this surface of infinite topological type). If time allows, I will give a description of the Gromov-boundary of the ray graph in terms of long rays in the plane minus a Cantor set. This involves joint work with Alden Walker.

Did you say Brouwer?

Series
Geometry Topology Seminar
Time
Monday, August 14, 2017 - 14:11 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Albert Fathi – Georgia Tech
We will give different topological very simple statements that seem not to have been noticed, although they are of the level of Brouwer’s fixed point theorem. The main result is: Let F be a compact subset of the manifold M. Assume g:F->M is a continuous map which is the identity on the boundary (or frontier) of F, then the image g(F) contains either F or M\F.

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