Tuesday, August 22, 2017 - 11:00 , Location: Skiles 006 , Juliette Bavard , University of Chicago , Organizer: Balazs Strenner
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.
Monday, August 14, 2017 - 14:11 , Location: Skiles 006 , Albert Fathi , Georgia Tech , Organizer: Dan Margalit
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.
Monday, August 7, 2017 - 14:05 , Location: Skiles Conference Room 114 , Ingrid Irmer , University of Melbourne , Organizer: Stavros Garoufalidis
Friday, July 7, 2017 - 10:30 , Location: Skiles 006 , Nick Vlamis , Michigan , Organizer: Justin Lanier
There has been a recent interest in studying surfaces of infinite type, i.e. surfaces with infinitely-generated fundamental groups. In this talk, we will focus on their mapping class groups, often called big mapping class groups. In contrast to the finite-type case, there are many open questions regarding the basic algebraic and topological properties of big mapping class groups. I will discuss several such questions and provide some answers. In particular, I will discuss automorphism groups of mapping class groups as well as relations between topological invariants of a surface and algebraic invariants of its mapping class group. The results in the talk are based on recent joint work with Priyam Patel and ongoing joint work with Javier Aramayona and Priyam Patel.
Tuesday, June 27, 2017 - 14:05 , Location: Skiles 006 , Lei Chen , University of Chicago , Organizer: Dan Margalit
I will talk about homomorphisms between surface braid groups. Firstly, we will see that any surjective homomorphism from PB_n(S) to PB_m(S) factors through a forgetful map. Secondly, we will compute the automorphism group of PB_n(S). It turns out to be the mapping class group when n>1.
Friday, June 23, 2017 - 10:00 , Location: Skiles 006 , William Worden , Temple University , email@example.com , Organizer: Justin Lanier
Certain fibered hyperbolic 3-manifolds admit a layered veering triangulation, which can be constructed algorithmically given the stable lamination of the monodromy. These triangulations were introduced by Agol in 2011, and have been further studied by several others in the years since. We present experimental results which shed light on the combinatorial structure of veering triangulations, and its relation to certain topological invariants of the underlying manifold. We will begin by discussing essential background material, including hyperbolic manifolds and ideal triangulations, and more particularly fibered hyperbolic manifolds and the construction of the veering triangulation.
Tuesday, June 20, 2017 - 14:05 , Location: Skiles 006 , Dan Margalit and Justin Lanier , Georgia Tech , Organizer: Justin Lanier
We give a simple geometric criterion for an element to normally generate the mapping class group of a surface. As an application of this criterion, we show that when a surface has genus at least 3, every periodic mapping class except for the hyperelliptic involution normally generates. We also give examples of pseudo-Anosov elements that normally generate when genus is at least 2, answering a question of D. Long.