2017 Dec 13

# Logic seminar - Omer Mermelstein - "Template structures for the class of Hrushovski ab initio geometries"

11:00am to 1:00pm

## Location:

Math 209
Zilber's trichotomy conjecture, in modern formulation, distinguishes three flavours of geometries of strongly minimal sets --- disintegrated/trivial, modular, and the geometry of an ACF. Each of these three flavours has a classic template'' --- a set with no structure, a projective space over a prime field, and an algebraically closed field, respectively. The class of ab initio constructions with which Hrushovski refuted the conjecture features a new flavour of geometries --- non-modular, yet prohibiting any algebraic structure.
2018 May 09

# Logic Seminar - Immanuel Benporat - "Arbault sets"

11:00am to 1:00pm

## Location:

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

# Combinatorics: Daniel Kalmanovich and Or Raz (HU) "2 talks back-to-back"

11:00am to 12:30pm

## Location:

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

# HD-Combinatorics Special Day: "Cohomology vanishing: from continuous to discrete", organized by Jozef Dodziuk

(All day)

## Location:

Room 130, IIAS, Feldman Building, Givat Ram
2018 Jun 05

# Tom Meyerovitch (BGU): On expansivness, topological dimension and mean dimesnion

2:15pm to 3:15pm

## Location:

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
2018 Apr 10

2:15pm to 3:15pm

2018 Apr 24

2:00pm to 3:00pm

2018 May 01

2:00pm to 3:00pm

2018 Apr 16

# NT&AG: Linda Frey (University of Basel), "Explicit Small Height Bound for Q(E_tor)"

2:00pm to 3:00pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
2018 Apr 09

# Combinatorics: David Ellis (Queen Mary) "Random graphs with constant r-balls"

11:00am to 12:30pm

## Location:

IIAS, room 130, Feldman Building, Givat Ram

2018 May 10

# Colloquium: Zemer Kosloff (Hebrew University) - "Poisson point processes, suspensions and local diffeomprhisms of the real line"

2:30pm to 3:30pm

## Location:

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

# Tamar Ziegler (Hebrew University) - "Concatenating cubic structure and polynomial patterns in primes"

2:30pm to 3:30pm

## Location:

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

# Colloquium: Gabriel Conant (Notre Dame) - "Pseudofinite groups, VC-dimension, and arithmetic regularity"

2:15pm to 3:15pm

## Location:

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 Jun 19

# Dynamics Lunch: Amichai Lampert (Huji) "Equidistribution of Zeros of Polynomials"

12:00pm to 1:00pm

## Location:

Manchester lounge
A classical theorem of Erdos and Turan states that if a monic polynomial has small values on the unit circle (relative to its constant coefficient), then its zeros cluster near the unit circle and are close to being equidistributed in angle. In February 2018, K. Soundararajan gave a short and elementary proof of their result using Fourier analysis. I'll present this new proof.
2018 May 01

# Dynamics Lunch: Ofir David (Huji) "On Minkowski's conjecture"

12:00pm to 1:00pm

## Location:

Manchester lounge
One of the first algorithm any mathematician learns about is the Euclidean division algorithm for the rational integer ring Z. When asking whether other integer rings have similar such division algorithms, we are then led naturally to a geometric interpretation of this algorithm which concerns lattices and their (multiplicative) covering radius.