2018 Jun 20

# Logic Seminar - Daniel Palacin - "On definable Bohr compactifications of ultraproducts of finite groups"

11:00am to 1:00pm

## Location:

Ross 63
Abstract: In this talk I will discuss some suitable definable Bohr compactification of an ultraproduct of finite groups, and relate it to ultra quasirandom groups.
2017 Apr 19

# Logic seminar- Shimon Garti, "Forcing axioms and saturated ideals"

4:00pm to 6:00pm

## Location:

Ross 70
Abstract: Paul Larson proved that under Martin's axiom and large continuum there are no Laver ideals over aleph_1. He asked about weakly Laver ideals under some forcing axiom.
We shall address two issues:
1. Under Martin's axiom and the continuum is above aleph_2, there are no weakly Laver ideals over aleph_1..
2. Under Baumgartner's axiom, the parallel of Larson's theorem holds for ideals over aleph_2.
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 Jan 24

# Logic Seminar - Vadim Kulikov - Borel Reducibility in Generalised Descriptive Set Theory"

11:00am to 1:00pm

## Location:

Ross 63

I will review some recent results in the Borel reducibility on uncountable cardinals of the Helsinki logic group.
Borel reducibility on the generalised Baire space \kappa^\kappa for uncountable \kappa is defined analogously to that for \kappa=\omega. One of the corollaries of this work is that under some mild cardinality assumptions on kappa, if T1 is classifiable and T2 is unstable or superstable with OTOP, then the ISOM(T1) is continuously reducible ISOM(T2) and ISOM(T2) is not Borel reducible to ISOM(T1).
2017 May 29

# Logic seminar - Ur Yaar, "A Toy Multiverse"

2:00pm to 4:00pm

## Location:

Shprinzak 101
We will present briefly the "multiverse view" of set theory, advocated by Hamkins, that there are a multitude of set-theoretic universes, and not one background universe, and his proposed "Multiverse Axioms". We will then move on to present the main result of Gitman and Hamkins in their paper "A natural model of the multiverse axioms" - that the countable computably saturated models of ZFC form a "toy model" of the multiverse axioms.
2018 Jun 06

# Logic Seminar - Gabriel Conant - "Local NIP group theory and pseudofinite groups"

11:00am to 1:00pm

## Location:

Ross 63
Much of the early development of model theoretic stability theory was motivated by stable groups, which include algebraic groups as guiding examples. Later work of Hrushovski and Pillay showed that many tools from stable group theory can be adapted to the local setting, where one works around a single stable formula rather than a stable theory. More recently, groups definable in NIP theories have been intensively studied, bringing back the importance of measures in model theory. On the other hand, local NIP group theory is not as well understood.
2017 May 24

# Logic seminar - Katrin Tent, "Ample geometries of finite Morley rank"

4:00pm to 6:00pm

## Location:

Ross 70
Abstract: I will explain the model theoretic notion of ampleness and present the geometric context of recent constructions.
2017 Nov 29

# Logic Seminar - Isabel Muller - "Zil'bers Conjecture and Building-like Geometries"

11:00am to 1:00pm

In an attempt to classify the geometries arising in strongly minimal sets, Zil'ber conjectured them to split into three different types: Trivial geometries, vector space-like geometries and field-like geometries. Soon after, Hrushovski refuted this conjecture while introducing a new construction method, which has been modified and used a lot ever since.
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 24

2:00pm to 3:00pm

2018 Apr 10

2:15pm to 3:15pm

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