2019
Sep
21

# Yuka received תולעת הפרק vaccination

10:15am to 11:15am

- 2019 Sep 21
# Yuka received תולעת הפרק vaccination

10:15am to 11:15am - 2019 Jun 27
# Groups and Dynamics seminar: Asaf Katz (Chicago) - An application of Margulis' inequality to effective equidistribution.

11:30am to 12:45pmAbstract: Ratner's celebrated equidistribution theorem states that the trajectory of any point in a homogeneous space under a unipotent flow is getting equidistributed with respect to some algebraic measure. In the case where the action is horospherical, one can deduce an effective equidistribution result by mixing methods, an idea that goes back to Margulis' thesis.

- 2019 Jun 27
# Group and dynamics seminar: Michael Chapman (HUJI): Cutoff on Ramanujan complexes

10:00am to 11:15am## Location:

Ross 70Abstract: A Markov chain over a finite state space is said to exhibit the total variation cutoff phenomenon if, starting from some Dirac measure, the total variation distance to the stationary distribution drops abruptly from near maximal to near zero. It is conjectured that simple random walks on the family of $k$-regular, transitive graphs with a two sided $\epsilon$ spectral gap exhibit total variation cutoff (for any fixed $k$ and $\epsilon). This is known to be true only in a small number of cases. - 2019 Jun 20
# Groups & dynamics seminar: Noam Kolodner (HUJI) - Surjectivity of morphisms of labeled core-graph under the action of automorphisms of a free group

10:00am to 11:00amFor a finitely generated subgroup H of the free group F_r, the Stallings graph of H is a finite combinatorial graph, whose edges are labeled by r letters (and their inverses), so that paths in the graphs correspond precisely to the words in H. Furthermore, there is a map between the graphs of two subgroups H and J, precisely when one is a subgroups of the other. Stallings theory studies the algebraic information which is encoded in the combinatorics of these graphs and maps. - 2019 Jun 16
# Yuka received תולעת הפרק vaccination

5:00pm to 6:00pm - 2019 Jun 13
# No seminar (IMU annual meeting)

10:00am to 11:10amAbstract: A Markov chain over a finite state space is said to exhibit the total variation cutoff phenomenon if, starting from some Dirac measure, the total variation distance to the stationary distribution drops abruptly from near maximal to near zero. It is conjectured that simple random walks on the family of $k$-regular, transitive graphs with a two sided $\epsilon$ spectral gap exhibit total variation cutoff (for any fixed $k$ and $\epsilon). This is known to be true only in a small number of cases. - 2019 Jun 12
# Seminar - Yoav Tamir

1:20pm to 2:20pm - 2019 Jun 06
# Groups and dynamics seminar - Yoav Gat (Technion) - Counting lattice points on the Heisenberg groups - A generalization of a classical problem to a non-commutative setting

10:00am to 11:00amAbstract: In this talk, I shall present a generalization of the lattice point counting problem for Euclidean balls in the context of a certain type of homogeneous groups, the so-called Heisenberg groups. - 2019 Jun 04
# Groups & dynamics seminar: Arie Levit(Yale) - Surface groups are flexibly stable

12:00pm to 1:00pmAbstract: A group G is stable in permutations if every almost-action of G on a finite set is close to some actual action. Part of the interest in this notion comes from the observation that a non-residually finite stable group cannot be sofic. I will show that surface groups are stable in a flexible sense, that is if one is allowed to "add a few extra points" to the action. This is the first non-trivial stability result for a non-amenable group. - 2019 May 21
# Special groups theory seminar: Abdalrazzaq R A Zalloum (Suny Buffalo) "Regular languages for hyperbolic-like geodesics".

4:00pm to 5:00pm## Location:

Ross 63Combinatorial group theory began with Dehn's study of surface groups, where he used arguments from hyperbolic geometry to solve the word/conjugacy problems. In 1984, Cannon generalized those ideas to all "hyperbolic groups", where he was able to give a solution to the word/conjugacy problem, and to show that their growth function satisfies a finite linear recursion. The key observation that led to his discoveries is that the global geometry of a hyperbolic group is determined locally: first, one discovers the local picture of G, then the recursive structure