Seminars

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.
2015 Nov 11

Logic seminar

Repeats every week every Wednesday until Tue Mar 28 2017 except Wed Nov 11 2015.
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Location: 

Ross 70
Reflections on the coloring and chromatic numbers Speaker: Chris Lambie-Hanson Abstract: Compactness phenomena play a central role in modern set theory, and the investigation of compactness and incompactness for the coloring and chromatic numbers of graphs has been a thriving area of research since the mid-20th century, when De Bruijn and Erdős published their compactness theorem for finite chromatic
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).
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.
2016 Dec 19

Special logic seminar - Elad Levi "Algebraic regularity lemma for hypergraphs"

10:00am to 12:00pm

Location: 

Sprinzak 101
Speaker: Elad Levi Algebraic regularity lemma for hypergraphs Abstract: Szemer´edi’s Regularity Lemma is a fundamental tool in graph theory. It states that for every large enough graph, the set of vertices has a partition A1,..,Ak, such that for almost every two subsets Ai,Aj the induced bipartite graph on (Ai,Aj) is regular, i.e. similar to a random bipartite graph up to a given error.
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 notion called “topological mean dimension’’ , introduced by Gromov and

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