2019 Apr 29

# Combinatoric: Karthik C. Srikanta (Weizmann Institute) "On Closest Pair Problem and Contact Dimension of a Graph"

11:00am to 1:00pm

## Location:

CS B-500, Safra campus
Speaker: Karthik C. Srikanta (Weizmann Institute)
Title: On Closest Pair Problem and Contact Dimension of a Graph
Abstract: Given a set of points in a metric space, the Closest Pair problem asks to find a pair of distinct points in the set with the smallest distance. In this talk, we address the fine-grained complexity of this problem which has been of recent interest. At the heart of all our proofs is the construction of a family of dense bipartite graphs with special embedding properties and are inspired by the construction of locally dense codes.
2019 Apr 08

# Combinatorics: Kim Minki (Technion) "The fractional Helly properties for families of non-empty sets"

11:00am to 1:00pm

## Location:

CS B-500, Safra campus
Speaker: Kim Minki, Technion
Title: The fractional Helly properties for families of non-empty sets
Abstract:
Let $F$ be a (possibly infinite) family of non-empty sets.
The Helly number of $F$ is defined as the greatest integer $m = h(F)$ for which there exists a finite subfamily $F'$ of cardinality $m$ such that every proper subfamily of $F'$ is intersecing and $F'$ itself is not intersecting.
For example, Helly's theorem asserts that the family of all convex sets in $d$-dimensional Euclidean space has Helly number $d+1$.
2019 Mar 25

# Combinatorics: Roy Meshulam (Technion) "Topology and combinatorics of the complex of flags"

11:00am to 1:00pm

## Location:

CS B-500, Safra campus
Speaker: Roy Meshulam (Technion)
Title: Topology and combinatorics of the complex of flags
Abstract:
2019 Mar 07

(All day)

2019 Mar 07

1:30pm to 2:30pm

Ross 70
2019 Mar 07

# Alexandre Danilenko (ILTPE) Forcing conservativeness of nonsingular Bernoulli shifts.

4:15pm to 5:15pm

Abstract: We first survey a recent progress related to the nonsingular Bernoulli transformations. Then we construct inductively new examples of conservative Bernoulli maps of type III. They appear as a limit of a sequence of Bernoulli maps of type II_1.
2019 Mar 07

# Emmanuel Roy (Paris 13) Non-singular Poisson suspensions

2:45pm to 3:45pm

## Location:

Ross 70
Poisson suspensions are random sets of points endowed with a transformation that displaces each point according to a single transformation of the sigma-finite space where the points lie. In this ongoing work, instead of dealing with measure-preserving transformations (which is the classical case), we are going to present our attempt to explore the non-singular case. The difficulties are counterbalanced by new tools that are trivial in the measure-preserving case but highly informative in the non-singular one.
2019 Apr 03

# Set Theory Seminar - Jialiang He (BIU), A combinatorial argument of p=t

2:00pm to 3:30pm

## Location:

Ross 63

Abstract:
The Minimal Tower Problem was one of most famous question in Cardinal
Invariants. We will present a combinatorial argument of this proof, which without using model theory
and forcing, motivated by Malliaris and Shelah's proof.
2019 Mar 10

# Ari Shnidman "Geometric expressions for derivatives of L-functions of automorphic forms" (after Yun and Zhang)

Repeats every week every Sunday until Sun Jun 23 2019 except Sun Apr 21 2019.
2:00pm to 4:00pm

2:00pm to 4:00pm
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Yun and Zhang compute the Taylor series expansion of an automorphic L-function over a function field, in terms of intersection pairings of certain algebraic cycles on the so-called moduli stack of shtukas. This generalizes the Waldspurger and Gross-Zagier formulas, which concern the first two coefficients.
2019 Mar 10

# Zlil Sela and Alex Lubotzky "Model theory of groups"

Repeats every week every Sunday until Sat Jun 29 2019 except Sun Apr 21 2019.
11:00am to 1:00pm

11:00am to 1:00pm
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Zlil Sela and Alex Lubotzky "Model theory of groups"
In the first part of the course we will present some of the main results in the theory of free,
hyperbolic and related groups, many of which appear as lattices in rank one simple Lie groups
We will present some of the main objects that are used in studying the theory of these groups,
and at least sketch the proofs of some of the main theorems.
In the second part of the course, we will talk about the model theory of lattices in high rank simple Lie groups.
2019 Apr 10

# Set Theory Seminar - Yair Hayut (KGRC) - Partial Strong Compactness

2:00pm to 3:30pm

## Location:

Ross 63

Abstract: The ultrafilter lemma, saying that every filter can be extended to an ultrafilter, is one of the fundamental consequences of the axiom of choice. By adding closure assumptions, and asking for extension of $\kappa$-complete filters to $\kappa$-complete ultrafilters, we obtain the notion of strongly compact cardinal, which has a very high consistency strength.
2019 Mar 14

# Manuel Luethi (ETH) : Effective equidistribution of primitive rational points along long horocycle orbits and disjointness to Kloosterman sums

10:00am to 11:30am

## Location:

Ross 70
Abstract: An observation by Jens Marklof shows that the primitive rational points of a fixed denominator along the periodic unipotent orbit of volume equal to the square of the denominator equidistribute inside a proper submanifold of the modular surface. This concentration as well as the equidistribution are intimately related to classical questions of number theoretic origin. We discuss the distribution of the primitive rational points along periodic orbits of intermediate size. In this case, we can show joint equidistribution with polynomial rate in the modular surface and in the torus.
2019 Apr 03

# Analysis Seminar: Malte Gerhold (Technion) "Dilations of q-commuting unitaries"

12:00pm to 1:00pm

## Location:

Ross 70
Title:
Dilations of q-commuting unitaries
Abstract:
Let (u,v) be a pair of unitary operators on a Hilbert space H such that vu=quv for a complex number q of modulus 1. For q' another complex number of modulus 1, we determine the smallest constant c>0 for which there exists a pair of q' commuting unitaries (U,V) on a larger Hilbert space K containing H such that (u,v) is the compression of (cU,cV) to H.
2019 Mar 19

# T&G: Viatcheslav Kharlamov (Strasbourg), Segre indices, Welschinger weights, and an invariant signed count of real lines on real projective hypersurfaces

1:00pm to 2:30pm

## Location:

Room 110, Manchester Building, Jerusalem, Israel
As it was observed a few years ago, there exists a certain signed count of real lines on real projective hypersurfaces of degree 2n+1 and dimension n that, contrary to the honest "cardinal" count, is independent of the choice of a hypersurface, and by this reason provides, as a consequence, a strong lower bound on the honest count. Originally, in this invariant signed count the input of a line was given by its local contribution to the Euler number of an appropriate auxiliary universal vector bundle.
2019 Jun 25

# Amitsur Memorial Symposium 2019

9:00am to 6:00pm

## Location:

Manchester House, Lecture Hall 2

#### The 26th Amitsur Memorial Symposium will be held at the Einstein Institute of Mathematics, the Hebrew University of Jerusalem.

Coordinators: Avinoam Mann, Aner Shalev