# Events & Seminars

# Special Talk : W Chacholski (Copenhagen) - "What is persistence?"

## Lecturer:

## Location:

# Basic Notions - Alex Lubotzky: "Group stability and approximation"

## Location:

# Barak Weiss (TAU): New examples for the horocycle flow on the moduli space of translation surfaces

# Combinatorics: Chris Cox (CMU) "Nearly orthogonal vectors"

## Location:

Title -- Nearly orthogonal vectors

Abstract -- How can $d+k$ vectors in $\mathbb{R}^d$ be arranged so that they are as close to orthogonal as possible? In particular, define $\theta(d,k):=\min_X\max_{x

# Combinatorics -- Erdos lecture cancelled; instead (NOTE THE TIME!) :

## Location:

Title: Sparsifiers - Part I (Part II from 2pm to 4pm, same day and place)

Abstract:

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.

* Multiplicative Sparsification and Triangular Rank;

* Karger-Benczur sparsification of cuts weights

# Combinatorics: Daniel Jerison (TAU) "Random walks on sandpile groups"

## Location:

Title: Random walks on sandpile groups

Abstract:

# Combinatorics: Roman Glebov (HU) "Perfect Matchings in Random Subgraphs of Regular Bipartite Graphs"

## Location:

Title: Perfect Matchings in Random Subgraphs of Regular Bipartite Graphs

Abstract:

Consider the random process in which the edges of a graph $G$ are

added one by one in a random order. A classical result states that if

$G$ is the complete graph $K_{2n}$ or the complete bipartite graph

$K_{n,n}$, then typically a perfect matching appears at the moment at

which the last isolated vertex disappears. We extend this result to

arbitrary $k$-regular bipartite graphs $G$ on $2n$ vertices for all

$k=\Omega(n)$.

# High-Dim Combinatorics: Stefan Glock, "Designs via iterative absorption"

# NT&AG: Max Gurevich (University of Singapore), "Branching laws for non-generic representations"

## Location:

# GAME THEORY AND MATHEMATICAL ECONOMICS RESEARCH SEMINAR:Michal Feldman, Tel Aviv University "Interdependent Values without Single-Crossing (Joint work with Alon Eden, Amos Fiat and Kira Goldner)"

## Location:

Abstract:

We consider a setting where an auctioneer sells a single item to n potential agents with {\em interdependent values}. That is, each agent has her own private signal, and the valuation of each agent is a function of all n private signals. This captures settings such as valuations for oil fields, broadcast rights, art, etc. Read more about GAME THEORY AND MATHEMATICAL ECONOMICS RESEARCH SEMINAR:Michal Feldman, Tel Aviv University "Interdependent Values without Single-Crossing (Joint work with Alon Eden, Amos Fiat and Kira Goldner)"

# Special Talk : Justin Noel (University of Regensburg) - "Blue-shift and thick tensor ideals"

## Lecturer:

## Location:

Abstract:

I will discuss a recent generalization of Kuhn's Blue-shift theorem about Tate cohomology. Combining this result with work of Arone, Dwyer, and Lesh we resolve a conjecture of Balmer and Sanders and classify the thick tensor ideals of compact genuine $A$-spectra, where $A$ is a finite abelian group. This is joint work with Tobias Barthel, Markus Hausmann, Niko Naumann, Thomas Nikolaus, and Nathaniel Stapleton.

# Tomasz Rzepecki (Uniwersytet Wrocławski): Topological dynamics and Galois groups in model theory

## Location:

I will briefly recall the required notions from topological dynamics. Some knowledge of model theory will help to understand the motivations, but otherwise, it will not be necessary.