Events & Seminars

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.
2017 Apr 24

Logic seminar

Repeats every week every Monday until Sun May 21 2017 except Mon May 01 2017.
12:00pm to 2:00pm

12:00pm to 2:00pm
12:00pm to 2:00pm

Location: 

Ross 63
We will take a close look at the first few steps of the construction of the Bristol model, which is a model intermediate to L[c], for a Cohen real c, satisfying V eq L(x) for all x.
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 22

Logic Seminar - Yair Hayut - "Chang's Conjecture at many cardinals simultaneously"

11:00am to 1:00pm

Location: 

Math 209







Chang's Conjecture is a strengthening of Lowenheim-Skolem-Tarski theorem. While Lowenheim-Skolem-Tarski theorem is provable in ZFC, any instance of Chang's Conjecture is independent with ZFC and has nontrivial consistency strength. Thus, the question of how many instances of Chang's Conjecture can consistently hold simultaneously is natural.


I will talk about some classical results on the impossibility of some instances of Chang's Conjecture and present some results from a joint work with Monroe Eskew.
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 27

Special logic seminar - Itaï BEN YAACOV, "Baby version of the asymptotic volume estimate"

10:00am to 12:00pm

Location: 

Shprinzak 102
I'll show how the Vandermonde determinant identity allows us to estimate the volume of certain spaces of polynomials in one variable (or rather, of homogeneous polynomials in two variables), as the degree goes to infinity. I'll explain what this is good for in the context of globally valued fields, and, given time constraints, may give some indications on the approach for the "real inequality" in higher projective dimension.
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 08

Logic Seminar- Itai Ben Yaacov - "Reconstruction for non-aleph0-categorical theories?"

11:00am to 1:00pm

Location: 

Math 209
It is a familiar fact (sometimes attributed to Ahlbrandt-Ziegler, though it is possibly older) that two aleph0-categorical theories are bi-interpretable if and only if their countable models have isomorphic topological isomorphism groups. Conversely, groups arising in this manner can be given an abstract characterisation, and a countable model of the theory (up to bi-interpretation, of course) can be reconstructed.
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
2018 Mar 21

Logic Seminar - Jorge Julián Prieto Jara - "Differentially closed fields and quasiminimality"

11:00am to 1:00pm

Location: 

Ross 63
Zilber introduced quasi-minimal classes to generalize the model theory of pseudo exponential fields. They are equipped with a pregeometry operator and satisfy interesting properties such as having only countable or co-countable definable sets. Differentially closed fields of characteristic 0, rich examples of a \omega-stable structures, are good candidates to be quasiminimal. The difficulty is that a differential equation may have uncountably many solutions, and thus violate the countable closure requirement of quasiminimal structures.

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