2017 Nov 06

4:00pm to 6:00pm

Room 130
2017 Nov 13

# HD-Combinatorics: Shmuel Weinberger, "L^2 cohomology"

2:00pm to 4:00pm

## Location:

Room 130, Feldman Building, Givat Ram
Abstract: I will give an introduction to the cohomology of universal covers of finite complexes. These groups are (for infinite covers) either trivial or infinite dimensional, but they have renormalized real valued Betti numbers. Their study is philosophically related to the topic of our year, and they have wonderful applications in geometry, group theory, topology etc and I hope to explain some of this.
2017 Nov 30

# Fedor Manin, "Introduction to quantitative topology"

9:00am to 10:00am

## Location:

Room 115, Feldman Building (IIAS), Givat Ram
2017 Oct 23

# Alex Lubotzky: High-Dimensional expanders and stability in group theory (course)

9:00am to 11:00am

## Location:

Feldman building, Eilat Hall
2017 Nov 20

# HD-Combinatorics: Ran Levi, "Neuro-Topology: An interaction between topology and neuroscience"

3:00pm to 4:00pm

## Location:

Room 130, Feldman Building, Givat Ram
Abstract: While algebraic topology is now well established as an applicable branch of mathematics, its emergence in neuroscience is surprisingly recent. In this talk I will present a summary of an ongoing joint project with mathematician and neuroscientists. I will start with some basic facts on neuroscience and the digital reconstruction of a rat’s neocortex by the Blue Brain Project in EPFL.
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
2017 Apr 19

# Logic seminar- Shimon Garti, "Forcing axioms and saturated ideals"

4:00pm to 6:00pm

## Location:

Ross 70
Abstract: Paul Larson proved that under Martin's axiom and large continuum there are no Laver ideals over aleph_1. He asked about weakly Laver ideals under some forcing axiom. We shall address two issues: 1. Under Martin's axiom and the continuum is above aleph_2, there are no weakly Laver ideals over aleph_1.. 2. Under Baumgartner's axiom, the parallel of Larson's theorem holds for ideals over aleph_2.
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 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.
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 Jul 26

# Logic seminar - Andrés Villaveces, "Around non-elementary dependence"

2:00pm to 4:00pm

## Location:

Ross 70
Dependent theories have now a very solid and well-established collection of results and applications. Beyond first order, the development of "dependency" has been rather scarce so far. In addition to the results due to Kaplan, Lavi and Shelah (dependent diagrams and the generic pair conjecture), I will speak on a few lines of current research around the extraction of indiscernibles for dependent diagrams and on various forms on dependence for abstract elementary classes. This is joint work with Saharon Shelah.