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 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.
2017 Nov 15

# Logic Seminar - Shimon Garti - " Length of Boolean algebras"

11:00am to 1:00pm

## Location:

Math 209
We shall prove that there is a sequence of Boolean algebras for which the ultraproduct of the lengths divided by an ultrafilter is strictly less than the length of the product algebra. This is a joint work with Saharon Shelah.
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.
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 30

# Logic Seminar - Gianluca Paolini - "On the Admissibility of a Polish Group Topology"

11:00am to 1:00pm

## Location:

Ross 63
In [Sh771] Shelah rediscovered an old result of Dudley on the non-admissibility of a Polish group topology on an uncountable free group. Crucial to his proof is a so-called Compactness Lemma for Polish groups, concerning satisfaction of algebraic equations for certain sequences of group elements converging to 0 (in distance).
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 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.
2018 Apr 11

# Logic Seminar - Shahar Oriel - "The infinite random simplicial complex"

11:00am to 1:00pm

## Location:

Ross 63
This talk will be a review of a paper by Andrew Brooke-Taylor and Damiano Testa
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.
2017 Dec 27

# Logic Seminar - Omer Ben-Neria - "Singular Stationarity and Set Theoretic Generalizations of Algebras"

11:00am to 1:00pm

## Location:

Ross 63
Abstract: The set theoretic generalizations of algebras have been introduced in the 1960s to give a set theoretic interpretation of usual algebraic structures. The shift in perspective from algebra to set theory is that in set theory the focus is on the collection of possible algebras and sub-algebras on specific cardinals rather than on particular algebraic structures. The study of collections of algebras and sub-algebras has generated many well-known problems in combinatorial set theory (e.g., Chang’s conjecture and the existence of small singular Jonsson cardinals).
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 Jul 10

# Special logic seminar - Noa Lavi, "Independent chapters in dependent theories"

11:00am to 1:00pm

## Location:

Ross 70
This talk is about three published papers of mine that form my phd. In the first two chapters I focus in the model theory of real closed fields and in the third one I take one step back and investigate in greater genearility dependent theories. The results are the following: 1. Boundedness criterion for rational functions over generalized semi-algebraic sets in real closed fields. 2. Positivity criterion for polynomials over generalized semi-algebraic sets in real closed valued fields.
2018 May 23

# Logic Seminar - Alejandro Poveda Ruzafa - "A Magidor-like study of $C^{(n)}$-cardinals"

11:00am to 1:00pm

## Location:

Ross 63
The notion of reflection plays a central role in modern Set Theory since the descovering of the well-known Lévy and Montague \textit{Reflection principle}. For any $n\in\omega$, let $C^{(n)}$ denote the class of all ordinals $\kappa$ which correctly interprets the $\Sigma_n$-statements of the universe, with parametes in $V_\kappa$.
2017 Mar 15

# Logic seminar - Rizos Sklinos, "Non-equational stable groups"

4:00pm to 6:00pm

## Location:

Ross 70
Non-equational stable groups. Speaker: Rizos Sklinos Abstract: The notion of equationality has been introduced by Srour and further developed by Pillay-Srour. It is best understood intuitively as a notion of Noetherianity on instances of first-order formulas. A first-order theory is equational when every first-order formula is equivalent to a boolean combination of equations. Equationality implies stability and for many years these two notions were identified, as only an "artificial" example of Hrushovski (a tweaked pseudo-space) was witnessing otherwise. Recently Sela proved that the