2018
Apr
11

# Logic Seminar - Shahar Oriel - "The infinite random simplicial complex"

11:00am to 1:00pm

## Location:

Ross 63

This talk will be a review of a paper by Andrew Brooke-Taylor and Damiano Testa:

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2018
Apr
11

11:00am to 1:00pm

Ross 63

This talk will be a review of a paper by Andrew Brooke-Taylor and Damiano Testa:

2017
Jul
10

11:00am to 1:00pm

Ross 70

This talk is about three published papers of mine that form my phd. In the first two chapters I focus in the model theory of real closed fields and in the third one I take one step back and investigate in greater genearility dependent theories.
The results are the following:
1. Boundedness criterion for rational functions over generalized semi-algebraic sets in real closed fields.
2. Positivity criterion for polynomials over generalized semi-algebraic sets in real closed valued fields.

2018
May
09

11:00am to 1:00pm

Ross 63

Arbault sets (briefly, A-sets) were first introduced by Jean Arbault in the context of Fourier analysis. One of his major results concerning these sets,asserts that the union of an A-set with a countable set is again an A-set. The next obvious step is to ask what happens if we replace the word "countable" by א_1. Apparently, an א_1 version of Arbault's theorem is independent of ZFC. The aim of this talk would be to give a proof (as detailed as possible) of this independence result. The main ingredients of the proof are infinite combinatorics and some very basic Fourier analysis.

2018
May
21

11:00am to 12:30pm

IIAS, Eilat hall, Feldman Building, Givat Ram

First speaker: Daniel kalmanovich, HU
Title: On the face numbers of cubical polytopes
Abstract:
Understanding the possible face numbers of polytopes, and of subfamilies of interest, is a fundamental question.
The celebrated g-theorem, conjectured by McMullen in 1971 and proved by Stanley (necessity) and by Billera and Lee (sufficiency) in 1980-81, characterizes the f-vectors of simplicial polytopes.

2018
Apr
09

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

2018
Apr
16

2018
Apr
09

2018
May
10

2:30pm to 3:30pm

Manchester Building (Hall 2), Hebrew University Jerusalem

The study of the representations theoretic properties of the group of diffeormorphisms of locally compact non compact Riemmanian manifolds which equal to the identity outside a compact set is is linked to a natural quasi invariant action of the group which moves all points of a Poisson point process according to the diffeomorphism (Gelfand-Graev-Vershik and Goldin et al.).
Neretin noticed that the local diffeomorphism group is a subgroup of a larger group which he called GMS and that GMS also acts in a similar manner on the Poisson point process.

2018
May
31

2:30pm to 3:30pm

Manchester Building (Hall 2), Hebrew University Jerusalem

A major difficulty in finding polynomial patterns in primes is the need to understand their distribution properties at short scales. We describe how for some polynomial configurations one can overcome this problem by concatenating short scale behavior in "many directions" to long scale behavior for which tools from additive combinatorics are available.

2018
Jun
07

2:15pm to 3:15pm

Manchester Building (Hall 2), Hebrew University Jerusalem

Given a set X, the notion of VC-dimension provides a way to measure randomness in collections of subsets of X. Specifically, the VC-dimension of a collection S of subsets of X is the largest integer d (if it exists) such that some d-element subset Y of X is ""shattered"" by S, meaning that every subset of Y can be obtained as the intersection of Y with some element of S. In this talk, we will focus on the case that X is a group G, and S is the collection of left translates of some fixed subset A of G.

2018
Apr
24