Wednesday, March 28, 2018 - 14:00 , Location: Skiles 006 , Justin Lanier , GaTech , Organizer: Anubhav Mukherjee
We will discuss a celebrated theorem of Sharkovsky: whenever a continuous self-map of the interval contains a point of period 3, it also contains a point of period n , for every natural number n.
Wednesday, March 14, 2018 - 14:00 , Location: Skiles 006 , Surena Hozoori , GaTech , Organizer: Anubhav Mukherjee
Assuming some "compatibility" conditions between a Riemannian metric and a contact structure on a 3-manifold, it is natural to ask whether we can use methods in global geometry to get results in contact topology. There is a notion of compatibility in this context which relates convexity concepts in those geometries and is well studied concerning geometry questions, but is not exploited for topological questions. I will talk about "contact sphere theorem" due to Etnyre-Massot-Komendarczyk, which might be the most interesting result for contact topologists.
Wednesday, March 7, 2018 - 14:00 , Location: Atlanta , Agniva Roy , GaTech , Organizer: Anubhav Mukherjee
Three dimensional lens spaces L(p,q) are well known as the first examples of 3-manifolds that were not known by their homology or fundamental group alone. The complete classification of L(p,q), upto homeomorphism, was an important result, the first proof of which was given by Reidemeister in the 1930s. In the 1980s, a more topological proof was given by Bonahon and Hodgson. This talk will discuss two equivalent definitions of Lens spaces, some of their well known properties, and then sketch the idea of Bonahon and Hodgson's proof. Time permitting, we shall also see Bonahon's result about the mapping class group of L(p,q).
Wednesday, February 28, 2018 - 14:00 , Location: Skiles 006 , Hyun Ki Min , GaTech , Organizer: Anubhav Mukherjee
I will introduce the notion of satellite knots and show that a knot in a 3-sphere is either a torus knot, a satellite knot or a hyperbolic knot.
Wednesday, February 21, 2018 - 14:00 , Location: Skiles 006 , Kevin Kodrek , GaTech , Organizer: Anubhav Mukherjee
There are a number of ways to define the braid group. The traditional definition involves equivalence classes of braids, but it can also be defined in terms of mapping class groups, in terms of configuration spaces, or purely algebraically with an explicit presentation. My goal is to give an informal overview of this group and some of its subgroups, comparing and contrasting the various incarnations along the way.
Wednesday, February 14, 2018 - 14:00 , Location: Skiles 006 , Anubhav Mukherjee , GaTech , Organizer: Anubhav Mukherjee
We will discuss the relationship between diffeomorphis groups of spheres and balls. And try to give an idea of existense of exotic structures on spheres.
Wednesday, February 7, 2018 - 13:55 , Location: Skiles 006 , Hyun Ki Min , GaTech , Organizer: Anubhav Mukherjee
The figure 8 knot is the simplest hyperbolic knot. In the late 1970s, Thurston studied how to construct hyperbolic manifolds from ideal tetrahedra. In this talk, I present the Thurston’s theory and apply this to the figure 8 knot. It turns out that every Dehn surgery on the figure 8 knot results in a hyperbolic manifold except for 10 exceptional surgery coefficients. If time permits, I will also introduce the classification of tight contact structures on these manifolds. This is a joint work with James Conway.
Wednesday, January 31, 2018 - 13:55 , Location: Skiles 006 , Sudipta Kolay , GaTech , Organizer: Anubhav Mukherjee
The Jordan curve theorem states that any simple closed curve decomposes the 2-sphere into two connected components and is their common boundary. Schönflies strengthened this result by showing that the closure of either connected component in the 2-sphere is a 2-cell. While the first statement is true in higher dimensions, the latter is not. However under the additional hypothesis of locally flatness, the closure of either connected component is an n-cell. This result is called the Generalized Schönflies theorem, and was proved independently by Morton Brown and Barry Mazur. In this talk, I will describe the proof of due to Morton Brown.
Wednesday, January 24, 2018 - 13:55 , Location: Skiles 006 , Justin Lanier , GaTech , Organizer: Anubhav Mukherjee
Take a map from the interval [0,1] to itself. Such a map can be iterated, and many phenomena (such as periodic points) arise. An interval self-map is an example of a topological dynamical system that is simple enough to set up, but wildly complex to analyze. In the late 1970s, Milnor and Thurston developed a combinatorial framework for studying interval self-maps in their paper "Iterated maps of the interval". In this talk, we will give an introduction to the central questions in the study of iterated interval maps, share some illustrative examples, and lay out some of the techniques and results of Milnor and Thurston.