2018 Jan 15

# HD-Combinatorics: Alexander Gamburd, "Arithmetic and Dynamics on Markoff-Hurwitz Varieties"

2:00pm to 4:00pm

## Location:

IIAS, Feldman Building, Givat Ram
Markoff triples are integer solutions to Markoff equation $x^2+y^2+z^2=3xyz$ which arose in Markoff's spectacular and fundamental work (1879) on diophantine approximation and has been henceforth ubiquitous in a tremendous variety of different fields in mathematics and beyond.
2017 Nov 06

4:00pm to 6:00pm

Room 130
2018 Mar 26

# NG&AT: Stephan Ehlen, TBA

2:00pm to 3:00pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
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.
2018 Jan 15

# NT&AG: Dmitry Vaintrob (IAS), "The log-coherent category and Hodge theory of open varieties"

2:00pm to 3:00pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
I will talk about a new Abelian category associated to an open variety with normal-crossings (or more generally, logarithmic) choice of compactification, which behaves in remarkable (and remarkably nice) ways with respect to changes of compactification and duality, and which first appeared in work on mirror symmetry.
2018 Jan 01

# NT&AG: Alexander Polischchuk (University of Oregon), "Associative Yang-Baxter equation and related 1-CY categories"

3:00pm to 4:00pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel
The talk is based on the joint work with Yanki Lekili. The associative Yang-Baxter equation is a quadratic equation related to both classical and quantum Yang-Baxter equations. It appears naturally in connection with triple Massey products in the derived category of coherent sheaves on elliptic curve and its degenerations. We show that all of its nondegenerate trigonometric solutions are obtained from Fukaya categories of some noncompact surfaces. We use this to prove that any two simple vector bundles on a cycle of projective lines are related by a sequence of spherical twists.
2017 Dec 13

# Logic seminar - Omer Mermelstein - "Template structures for the class of Hrushovski ab initio geometries"

11:00am to 1:00pm

## Location:

Math 209
Zilber's trichotomy conjecture, in modern formulation, distinguishes three flavours of geometries of strongly minimal sets --- disintegrated/trivial, modular, and the geometry of an ACF. Each of these three flavours has a classic template'' --- a set with no structure, a projective space over a prime field, and an algebraically closed field, respectively. The class of ab initio constructions with which Hrushovski refuted the conjecture features a new flavour of geometries --- non-modular, yet prohibiting any algebraic structure.
2017 Dec 28

# Amitsur Algebra: Ari Shnidman (Boston College), "The behavior of rational points in one-parameter families"

12:00pm to 1:00pm

## Location:

Ross 70, Math Building, Givat Ram
Title: The behavior of rational points in one-parameter families Abstract: How often does a "random" algebraic plane curve f(x,y) = 0 have a solution with rational coordinates? In one-parameter "twist" families of elliptic curves, Goldfeld conjectured that there should be a rational point exactly half of the time. Recent progress towards this conjecture makes use of Selmer groups, and I'll explain the geometric idea underlying their construction. I'll also describe results for families of curves of higher genus, and abelian varieties of higher dimension.
2017 Dec 06

# Logic Seminar - Daoud Siniora - "Automorphism groups of homogeneous structures"

11:00am to 1:00pm

## Location:

Math 209
A special class among the countably infinite relational structures is the class of homogeneous structures. These are the structures where every finite partial isomorphism extends to a total automorphism. A countable set, the ordered rationals, and the random graph are all homogeneous.
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.
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.