2019 Nov 25

# Combinatorics: Itamar Vigdorovich (Weizmann)

10:00am to 12:00pm

## Location:

C-400, CS building

Speaker: Itamar Vigdorovich (Weizmann)

Title: Complexes, Lie groups, lattices and quantum homological codes

Abstract:
2019 Nov 11

# Combinatorics: Barak Weiss (TAU)

10:00am to 12:00pm

## Location:

C-400, CS building

Speaker: Barak Weiss (TAU)

Title:  New bounds on the covering radius of a lattice.

Abstract:

We obtain new upper bounds on the minimal density of lattice coverings of R^n by dilates of a convex body K. We also obtain bounds on the probability (with respect to the natural Haar-Siegel measure on the space of lattices) that a randomly chosen lattice L satisfies L + K = R^n. As a step in the proof, we utilize and strengthen results on the discrete Kakeya problem. This is joint work with Or Ordentlich and Oded Regev.

2019 Nov 26

# Zvi Shem Tov (UBC): Quantum unique ergodicity for SL(2,Z)/H (following Soundararajan)

12:00pm to 1:00pm

2020 Jan 28

# Uri Bader (Weizmann) - The evolution of Margulis Normal Subgroup Theorem and non-commutative ergodic theory, following Peterson and Boutonnet-Houdayer

12:00pm to 1:00pm

This will be more of a survey talk than usual, but one relevant paper is
https://arxiv.org/abs/1908.07812
2019 Nov 05

# Karim Adiprasito (HUJI): A discrete billiard problem from scientific computing

12:00pm to 1:00pm

2019 Oct 28

# Combinatorics: Zlil Sela (HUJI) "Combinatorics and geometry in non-commutative algebraic geometry"

10:00am to 12:00pm

## Location:

CS building, room C-221
Speaker: Zlil Sela, HUJI
Title: Combinatorics and geometry in non-commutative algebraic geometry
Abstract:
2020 Apr 30

# Colloquium: (CANCELLED)

2:30pm to 3:30pm

## Location:

Manchester Building (Hall 2), Hebrew University Jerusalem
2019 Oct 31

# Groups & Dynamics seminar - Vincent Guirardel (Universite de Rennes 1) "Measure Equivalence rigidity for Out(Fn)"

10:00am to 11:00am

## Location:

Ross 70
Abstract:
Measure equivalence of countable groups is a measure theoretic analogue
of quasi-isometry.
For example, any two lattices in the same Lie group are by definition
measure equivalent.
We prove that any countable group that is measure equivalent to Out(Fn)
is virtually isomorphic to Out(Fn). This is a joint work with Camille
Horbez.
2019 Oct 29

# Zemer Kosloff, Finitary isomorphisms of Brownian motions

2:00pm to 3:00pm

Ornstein and Shields (Advances in Math., 10:143-146, 1973) proved that Brownian motion reflected on a bounded region is an infinite entropy Bernoulli flow and thus Ornstein theory yielded the existence of a measure-preserving isomorphism between any two such Brownian motions. For fixed h >0, we construct by elementary methods, isomorphisms with almost surely finite coding windows between Brownian motions reflected on the intervals [0, qh] for all positive rationals q. This is joint work with Terry Soo.
2019 Nov 19

# Tom Meyerovitch (BGU), Efficient finitary codings by Bernoulli processes

2:00pm to 3:00pm

Abstract:
Recently Uri Gabor refuted an old conjecture stating that any
finitary factor of an i.i.d process is finitarly isomorphic to an
i.i.d process. Complementing Gabor's result,
in this talk, which is based on work in progress with Yinon Spinka,
we will prove that any countable-valued process which is admits a
finitary a coding by some i.i.d process furthermore admits an
$\epsilon$-efficient finitary coding, for any positive $\epsilon$.
Here an `$\epsilon$-efficient coding'' means that the entropy
2019 Nov 26

2:00pm to 3:00pm

Ross 70

2019 Oct 31

# Basic Notions: Gil Kalai (HUJI) "Classical and quantum computation"

4:00pm to 5:15pm

## Location:

Ross 70
In the lecture I will describe basic notions of computational complexity:
Boolean functions, basic algorithmic tasks, Boolean circuits, P, NP, randomness, quantum circuits, noisy quantum circuits, bounded depth circuits, and more.
If time permits I will describe some (or more realistically one) mathematical challenge in the field and briefly
describe some examples (more realistically, one example) on how theory meets reality.
2019 Dec 25

# Analysis Seminar: Adi Glucksam (Toronto) "Optimal growth of frequently oscillating subharmonic functions"

12:00pm to 1:00pm

## Location:

Ross 70

Title: Optimal growth of frequently oscillating subharmonic functions.

Abstract: In this talk I will present Nevanlinna-type tight bounds on the minimal possible growth of subharmonic functions with a large zero set.  We use a technique inspired by a paper of Jones and Makarov.
2019 Dec 03

# Uri Gabor (HUJI) - A measurable-group-theoretic solution to von Neumann’s problem (following D. Gaboriau and R. Lyons)

12:00pm to 1:00pm

2019 Nov 12

# Uri Gabor (HUJI), On the failure of Ornstein's theory in the finitary category.

2:00pm to 3:00pm

Abstract: In this talk, I'll show the invalidity of finitary counterparts for three main theorems in classification theory: The preservation of being a Bernoulli shift through factors, Sinai's factor theorem, and the weak Pinsker property. This gives a negative answer to an old conjecture and to a recent open problem.