Events & Seminars

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.

 
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.
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).
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.
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.
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 Dec 07

Combinatorics: Shira Zerbib Gelaki (MSRI, U. Michigan) "Colorful coverings of polytopes -- the hidden topological truth behind different colorful phenomena"

12:00pm to 1:00pm

Location: 

Room 101 in Sprinzak
Speaker: Shira Zerbib Gelaki (MSRI, University of Michigan) Title: Colorful coverings of polytopes -- the hidden topological truth behind different colorful phenomena Abstract: The topological KKMS Theorem is a powerful extension of the Brouwer's Fixed-Point Theorem, which was proved by Shapley in 1973 in the context of game theory. We prove a colorful and polytopal generalization of the KKMS Theorem, and show that our theorem implies some seemingly unrelated results in discrete geometry and combinatorics involving colorful settings.
2016 Dec 05

NT&AG: Michael Temkin (Hebrew University), "Topological transcendence degree"

2:00pm to 3:00pm

Abstract: my talk will be devoted to a basic theory of extensions of complete real-valued fields L/K. Naturally, one says that L is topologically-algebraically generated over K by a subset S if L lies in the completion of the algebraic closure of K(S). One can then define topological analogues of algebraic independence, transcendence degree, etc. These notions behave much more wierd than their algebraic analogues. For example, there exist non-invertible continuous K-endomorphisms of the completed algebraic closure of K(x). In my talk, I will tell which part
2017 Jun 19

NT&AG: Ehud de Shalit (HUJI) "Ordinary foliations on unitary Shimura varieties"

2:00pm to 3:00pm

Abstract: Inseparable morphisms proved to be an important tool for the study of algebraic varieties in characteristic p. In particular, Rudakov-Shafarevitch, Miyaoka and Ekedahl have constructed a dictionary between "height 1" foliations in the tangent bundle and "height 1" purely inseparable quotients of a non-singular variety in characteristic p. In a joint work with Eyal Goren we use this dictionary to study the special fiber S of a unitary Shimura variety of signature (n,m), m < n, at a prime p which is inert in the underlying imaginary quadratic field. We
2016 Nov 28

NT&AG: Boris Zilber (University of Oxford), "On algebraically closed field of characteristic 1"

2:00pm to 3:00pm

Location: 

Ros Building, 70A
Abstract: I will start with a motivation of what algebraic (and model-theoretic) properties an algebraically closed field of characteristic 1 is expected to have. Then I will explain how these properties can be obtained by the well-known in model theory Hrushovski's construction and then formulate very precise axioms that such a field must satisfy. The axioms have a form of statements about existence of solutions to systems of equations in terms of a 'multi-dimansional' valuation theory and the validity of these statements is an open problem to be discussed.
2017 Apr 03

NT&AG: Izzet Coskun (University of Illinois at Chicago), "Birational geometry of moduli spaces of sheaves on surfaces"

4:00pm to 5:00pm

Location: 

Tel Aviv University, Schreiber building, 209
Abstract: In the last five years Bridgeland stability has revolutionized our understanding of the geometry of moduli spaces of sheaves on surfaces, allowing us to compute ample and effective cones and describe different birational models. In this talk, I will survey some of my joint work with Daniele Arcara, Aaron Bertram, Jack Huizenga and Matthew Woolf on the birational geometry of moduli spaces of sheaves on the plane. I will describe the ample and effective cones of these moduli spaces, concentrating on Hilbert schemes of points and concrete examples.

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