# Events & Seminars

# HD-Combinatorics: Special day on sparsification (by Ilan Newman and Yuri Rabinovich)

## Location:

*Special day on sparsification*

Speakers:

**Ilan Newman**and

**Yuri Rabinovich**.

Part I: 10:30 - 12:30

Part II: 14:00 - 15:50

*Abstract for the day:*

Time permitting, we plan to discuss the following topics (in this order):

1.

* Additive Sparsification and VC dimension

* Multiplicative Sparsification

* Examples: cut weights, cut-dimension of L_1 metrics, general metrics,

and their high-dimensional analogues

2.

# IIAS outreach lecture: Prof. Gil Kalai "Sailing into High Dimensions"

## Lecturer:

## Location:

We will explain what high dimensions are, and describe some questions and answers in geometry and combinatorics of the high dimensional world.

# No Basic notions seminar - deferred to 25.6

# Basic Notions: Elon Lindenstrauss (HUJI) : Effective Equidistribution of closed orbits, property tau, and other applications

## Location:

# Elon Lindenstrauss (HUJI) - Effective Equidistribution and property tau

# CS Theory -- Erdős Lecture II: Counting contigency tables

## Lecturer:

## Location:

Contingency tables are matrices with fixed row and column sums. They are in natural correspondence with bipartite multi-graphs with fixed degrees and can also be viewed as integer points in transportation polytopes. Counting and random sampling of contingency tables is a fundamental problem in statistics which remains unresolved in full generality.

In the talk, I will review both asymptotic and MCMC approaches, and then present a new Markov chain construction which provably works for sparse margins. I conclude with some curious experimental results and conjectures. Read more about CS Theory -- Erdős Lecture II: Counting contigency tables