2018 May 08

# Dynamics Seminar: Tsviqa Lakrec (Huji)

12:00pm to 1:00pm

## Location:

Manchester 209
Consider a simple random walk on $\mathbb{Z}$ with a random coloring of $\mathbb{Z}$.
Look at the sequence of the first $N$ steps taken and colors of the visited locations.
From it, you can deduce the coloring of approximately $\sqrt{N}$ integers.
Suppose an adversary may change $\delta N$ entries in that sequence. What can be deduced now?
We show that for any $\theta<0.5,p>0$, there are $N_{0},\delta_{0}$
such that if $N>N_{0}$ and $\delta<\delta_{0}$ then with probability $>1-p$ we can reconstruct
2018 Apr 26

# Basic Notions: Alex Lubotzky "From expander graphs to high dimensional expanders: a road map"

4:00pm to 5:30pm

## Location:

Math Hall 2
Expander graphs have been a topic of great interest in the last 50 years for mathematicians and computer scientists. In recent years a high dimensional theory is emerging.  We will describe some of its main directions and questions.
2018 May 16

# Analysis Seminar: Nadav Dym (WIS) "Linear algorithms for computing conformal mappings"

12:00pm to 1:00pm

## Location:

Ross Building
Abstract:
(joint with Noam Aigerman, Raz Sluzky and Yaron Lipman)
2018 May 29

# Dynamics Lunch: Matan Seidel (Huji) - "The Mass Transport Principle in Percolation Theory"

12:00pm to 1:00pm

## Location:

Manchester lounge
The Mass Transport Principle is a useful technique that was introduced to the study of automorphism-invariant percolations by Häggström in 1997. The technique is a sort of mass conservation principle, that allows us to relate random properties (such as the random degree of a vertex) to geometric properties of the graph.
I will introduce the principle and the class of unimodular graphs on which it holds, as well as a few of its applications.
2018 Apr 16

# Special talk: Yonatan Harpaz (Paris 13) - "Towards a universal property for Hermitian K-theory"

## Lecturer:

Yonatan Harpaz (Paris 13)
4:30pm to 5:30pm

## Location:

Ross 70

Abstract: Hermitian K-theory can be described as the "real" analogue of algebraic K-theory, and plays a motivic role similar to the role played by real topological K-theory in classical stable homotopy theory. However, the abstract framework surrounding and supporting Hermitian K-theory is less well understood than its algebraic counterpart, especially in the case when 2 is not assumed to be invertible in the ground ring.

2018 Jun 27

# Analysis Seminar: Barry Simon (Caltech) "Heinävarra’s Proof of the Dobsch–Donoghue Theorem"

12:00pm to 1:00pm

## Location:

Ross Building, Room 70
Abstract:
In 1934, Loewner proved a remarkable and deep theorem about matrix monotone functions. Recently, the young Finnish mathematician, Otte Heinävarra settled a 10 year old conjecture and found a 2 page proof of a theorem in Loewner theory whose only prior proof was 35 pages. I will describe his proof and use that as an excuse to discuss matrix monotone and matrix convex functions including, if time allows, my own recent proof of Loewner’s original theorem.
2018 May 29

# Yuri Lima (Paris 11): Symbolic dynamics for non-uniformly hyperbolic systems with singularities

2:15pm to 3:15pm

## Location:

Ross 70
Symbolic dynamics is a tool that simplifies the study of dynamical systems in various aspects. It is known for almost fifty years that uniformly hyperbolic systems have good'' codings. For non-uniformly hyperbolic systems, Sarig constructed in 2013 good'' codings for surface diffeomorphisms. In this talk we will discuss some recent developments on Sarig's theory, when the map has discountinuities and/or critical points, such as multimodal maps of the interval and Bunimovich billiards.
2018 May 08

# Dynamics Seminar: Yinon Spinka (TAU): Finitary codings of Markov random fields

2:15pm to 4:15pm

## Location:

Ross 70

Let X be a stationary Z^d-process. We say that X is a factor of an i.i.d. process if there is a (deterministic and translation-invariant) way to construct a realization of X from i.i.d. variables associated to the sites of Z^d. That is, if there is an i.i.d. process Y and a measurable map F from the underlying space of Y to that of X, which commutes with translations of Z^d and satisfies that F(Y)=X in distribution. Such a factor is called finitary if, in order to determine the value of X at a given site, one only needs to look at a finite (but random) region of Y.
2018 Apr 12

# Special talk: Yonatan Harpaz (Paris 13) - "Small extensions in algebra and topology"

## Lecturer:

Yonatan Harpaz (Paris 13)
1:15pm to 2:15pm

## Location:

Ross 70
Abstract: In this talk, we will discuss the notion of small extensions in its various incarnations, from torsors under abelian groups to square-zero extensions of algebras. We will then focus on the somewhat less familiar case of small extensions of ∞-categories. Our main goal is to make this abstract concept concrete and intuitive through a variety of examples. In particular, we will advocate the point of view that small extensions of  ∞-categories offer a unifying perspective in understanding many constructions appearing in obstruction, classification, and deformation theoretic problems
2018 Apr 16

# HD-Combinatorics Special Day on Grassman Expanders and Unique Games (organized by Irit Dinur)

(All day)

## Location:

Room 130, IIAS, Feldman Building, Givat Ram
2018 Apr 11

4:00pm to 6:00pm

Ross 70A
2018 Apr 15

# GAME THEORY AND MATHEMATICAL ECONOMICS RESEARCH SEMINAR: Ron Peretz, Bar Ilan University: "The Rate of Innovation Diffusion in Social Networks (joint with Itai Arieli, Yakov Babichenko, and Peyton H Young)"

1:30pm to 2:30pm

## Location:

Elath Hall, 2nd floor, Feldman Building, Edmond Safra Campus
2018 May 22

# Dynamics Lunch: Tsviqa Lakrec (Huji)

12:00pm to 1:00pm

## Location:

Manchester lounge