The Dynamics & Probability Seminar meets every Tuesday at 14:15 at Ross 70.

The HUJI dynamics group webpage can be found here.

2018
Nov
13

# Dynamics Seminar: Amir Algom (HUJI)

2:15pm to 3:15pm

The HUJI dynamics group webpage can be found here.

2018
Nov
13

2:15pm to 3:15pm

2018
Dec
04

2:15pm to 3:15pm

2018
Oct
23

2:15pm to 3:15pm

2018
Nov
20

2:15pm to 3:15pm

2018
Jun
26

2:15pm to 3:15pm

Suppose that a countable group $G$ acts on a compact metric space $X$ and that $S \subset G$ is a semigroup not containing the identity of $G$. If every continuous function $f$ on $X$ is contained in the closed algebra generated by $\{sf : s \in S\}$, the action is said to be $S$-predictable.
In this talk, we consider the following question due to Hochman:
When $G$ is amenable, does $S$-predictability imply zero topological entropy?
To provide an affirmative answer, we introduce the notion of a random invariant order.

2018
May
22

2:15pm to 3:15pm

A longstanding open question concerning the horocycle flow on moduli space of translation surfaces, is whether one can classify the invariant measures and orbit-closures for this action. Related far-reaching results of Eskin, Mirzakhani and Mohammadi indicated that the answer might be positive. However, in recent work with Jon Chaika and John Smillie, we find unexpected examples of orbit-closures; e.g. orbit closures which are not generic for any measure, and others which have fractional Hausdorff dimension. Such examples exist even in genus 2.

2018
May
08

12:00pm to 1:00pm

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
the coloring of $>N^{\theta}$ integers.

2018
Jun
19

2:15pm to 3:15pm

Ross 70

In recent years, topological dynamics have become an important tool in model theory. I will talk about some topological dynamical results from my PhD thesis about the so-called group-like equivalence relations. I plan to give a glimpse of the motivations in model theory (mostly related to the model-theoretic Galois groups and connected components of definable groups) and to show some ideas of the proofs.
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.

2018
May
15

2:15pm to 3:15pm

2018
May
29

2:15pm to 3:15pm

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

2:15pm to 4:15pm

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
Jun
05

2:15pm to 3:15pm

Ross 70

Expansivness is a fundamental property of dynamical systems.
It is sometimes viewed as an indication to chaos.
However, expansiveness also sets limitations on the complexity of a system.
Ma\~{n}'{e} proved in the 1970’s that a compact metric space that
admits an expansive homeomorphism is finite dimensional.
In this talk we will discuss a recent extension of Ma\~{n}'{e}’s
theorem for actions generated by multiple homeomorphisms,
based on joint work with Masaki Tsukamoto. This extension relies on a
notion called “topological mean dimension’’ , introduced by Gromov and

2018
Apr
10

2018
Apr
24

2:00pm to 3:00pm

2018
May
01

2:00pm to 3:00pm