Events & Seminars

2018 Jun 27

Logic Seminar - Shahar Oriel - "Erdos-Hajnal property for stable graphs"

11:00am to 1:00pm

Location: 

Ross 63
We will follow a short note by Artem Chernikov & Sergei Starchenko: "A note on the Erdos-Hajnal Conjecture." “In this short note we provide a relatively simple proof of the Erd ̋os–Hajnal conjecture for families of finite (hyper-)graphs without the m-order property. It was originally proved by M. Malliaris and S. Shelah”
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 13

Logic Seminar - Nick Ramsey - "Keisler measures in simple theories"

11:00am to 1:00pm

Location: 

Ross 63
Keisler measures were introduced in the late 80's by Keisler but they became central objects in model theory only recently with the development of NIP theories. This led naturally to the question of whether there might be a parallel theory of measures in other tame classes, especially in the simple theories where pseudofinite counting measures supply natural and interesting examples. We will describe some first steps toward establishing such a theory, based on Keisler randomizations and the theory of independence for NSOP1 theories in continuous logic.
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.
2017 Jun 28

Logic seminar - Shimon Garti, "Tiltan"

4:00pm to 6:00pm

Location: 

Ross 70
We shall try to prove some surprising (and hopefully, correct) theorems about the relationship between the club principle (Hebrew: tiltan) and the splitting number, with respect to the classical s at omega and the generalized s at supercompact cardinals.
2016 Dec 28

Logic seminar - Matthew Foreman, "Better lucky than smart: realizing a quasi-generic class of measure preserving transformations as diffeomorphisms"

4:00pm to 6:00pm

Location: 

Ross 70
Better lucky than smart: realizing a quasi-generic class of measure preserving transformations as diffeomorphisms. Speaker: Matthew Foreman Abstract: In 1932, von Neumann proposed classifying measure preserving diffeomorphisms up to measure isomorphism. Joint work with B. Weiss shows this is impossible in the sense that the corresponding equivalence relation is not Borel; hence impossible to capture using countable methods.
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 10

Logic Seminar - Alex Lubotzky - "First order rigidity of high-rank arithmetic groups"

11:00am to 1:00pm

Location: 

Ross 63
The family of high rank arithmetic groups is a class of groups playing an important role in various areas of mathematics. It includes SL(n,Z), for n>2 , SL(n, Z[1/p] ) for n>1, their finite index subgroups and many more. A number of remarkable results about them have been proven including; Mostow rigidity, Margulis Super rigidity and the Quasi-isometric rigidity.
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. This is a joint work with Shimon Garti and Omer Ben-Neria.
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 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.
2017 Nov 01

Logic Seminar - Immanuel BenPorat - "Cardinal conditions for strong Fubini theorems"

11:00am to 1:00pm

Location: 

Math209
This talk will be largely based on a paper by Joseph Shipman with the same title. We will discuss some variations of Fubini type theorems. The focus will be on what is known as "strong Fubini type theorems". Apparently these versions were proved to be independent of ZFC,and our main aim will be to sketch a proof of this result. We will assume basic knowledge in measure theory. Aside from that, the material is rather self contained.

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