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:**

Edmond J. Safra Campus The Hebrew University of Jerusalem

2019
Nov
25

10:00am to 12:00pm

C-400, CS building

2019
Nov
11

10:00am to 12:00pm

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

2020
Jan
28

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

https://arxiv.org/abs/1908.07812

2019
Nov
05

2019
Oct
28

10:00am to 12:00pm

CS building, room C-221

Speaker: Zlil Sela, HUJI

Title: Combinatorics and geometry in non-commutative algebraic geometry

Abstract:

Title: Combinatorics and geometry in non-commutative algebraic geometry

Abstract:

2020
Apr
30

2019
Oct
31

10:00am to 11:00am

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.

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

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

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

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

2019
Oct
31

4:00pm to 5:15pm

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.

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

12:00pm to 1:00pm

Ross 70

Title: Optimal growth of frequently oscillating subharmonic functions.

Abstract

2019
Dec
03

2019
Nov
12

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.

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