• 2019 Jun 25

# Amitsur Memorial Symposium 2019

9:00am to 6:00pm

## Location:

Manchester House, Lecture Hall 2

#### The 26th Amitsur Memorial Symposium will be held at the Einstein Institute of Mathematics, the Hebrew University of Jerusalem.

Coordinators: Avinoam Mann, Aner Shalev

• 2019 Jun 25

# Dynamics Lunch: Michael Chapman ״Markoff triples״

12:00pm to 1:00pm

Partially based on the paper "The Markoff Group of Transformations in Prime and Composite Moduli" by Meiri and Puder.
• 2019 Jun 26

(All day)

• 2019 Jun 26

# Logic Seminar - tba

11:00am to 1:00pm

Ross 63
• 2019 Jun 26

# Analysis Seminar - Dvoretzky lecture - Assaf Naor "The (in)compatibility of 3 and 5 dimensional Heisenberg geometry with Lebesgue spaces"

12:00pm to 1:00pm

## Location:

Ross 70
Title: The (in)compatibility of 3 and 5 dimensional Heisenberg geometry with Lebesgue spaces Abstract: The 3-dimensional (discrete) Heisenberg geometry is the shortest-path metric on the infinite graph whose vertex set is the integer grid $\Z^3$ and the neighbors of each integer vector $(a,b,c)$ are the four integer vectors $$(a+ 1,b,c), (a- 1,b,c), (a,b+ 1,c+ a), (a,b- 1,c- a).$$
• 2019 Jun 26

# Minicourse: Jared Weinstein (Boston University "Geometrization of the local Langlands program"

2:00pm to 4:00pm

## Location:

Ross 70
Prof. Jared Weinstein (Boston University) will give a series of 3 talks titled "Geometrization of the local Langlands program"
• 2019 Jun 27

# Group and dynamics seminar: Michael Chapman (HUJI): Cutoff on Ramanujan complexes

10:00am to 11:15am

## Location:

Ross 70
Abstract: 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 27

# Groups and Dynamics seminar: Asaf Katz (Chicago) - An application of Margulis' inequality to effective equidistribution.

11:30am to 12:45pm

Abstract: 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

# Colloquium Dvoretzky lecture: Assaf Naor(Princeton) - An average John theorem

2:30pm to 3:30pm

## Location:

Manchester Building (Hall 2), Hebrew University Jerusalem

Abstract: We will prove a sharp average-case variant of a classical embedding theorem of John through the theory of nonlinear spectral gaps. We will use this theorem to provide a new answer to questions of Johnson and Lindenstrauss (1983) and Bourgain (1985) on metric dimension reduction, and explain how it leads to algorithms for approximate nearest neighbor search.
• 2019 Jun 27

# Basic Notions: Hillel Furstenberg (HUJI) : "Affine (Convex) representations and harmonic functions on symmetric spaces." Part 2

4:00pm to 5:15pm

## Location:

Ross 70
Classical group representation theory deals with group actions on linear spaces; we consider group actions on compact convex spaces, preserving topological and convex structure. We focus on irreducible actions, and show that for a large class of groups - including connected Lie groups - these can be determined. There is a close connection between this and the theory of bounded harmonic functions on symmetric spaces and their boundary values.