Events & Seminars

2017 Jul 26

Logic seminar - Andrés Villaveces, "Around non-elementary dependence"

2:00pm to 4:00pm

Location: 

Ross 70
Dependent theories have now a very solid and well-established collection of results and applications. Beyond first order, the development of "dependency" has been rather scarce so far. In addition to the results due to Kaplan, Lavi and Shelah (dependent diagrams and the generic pair conjecture), I will speak on a few lines of current research around the extraction of indiscernibles for dependent diagrams and on various forms on dependence for abstract elementary classes. This is joint work with Saharon Shelah.
2017 Mar 01

Logic seminar - Yair Hayut, "Weak Prediction Principles"

4:00pm to 6:00pm

Location: 

Ross 70
Weak Prediction Principles
Speaker: Yair Hayut
Abstract: Jensen's diamond is a well studied prediction principle. It holds in L (and other core models), and in many cases it follows from local instances of GCH.
In the talk I will address a weakening of diamond (due to Shaleh and Abraham) and present Abraham's theorem about the equivalence between weak diamond and a weak consequence of GCH. Abraham's argument works for successor cardinals. I will discuss what is known and what is open for inaccessible cardinals.
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 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 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.

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