2019 May 21

# Landau Lecture 3: Liftings mod p2 and the Nygaard filtration

## Lecturer:

Prof. Luc Illusie (Université Paris-Sud)
1:00pm to 2:00pm

## Location:

Ross 70

### Liftings mod p2 and the Nygaard filtration

Abstract: I will revisit old results on liftings mod p2 and decompositions of de Rham complexes in positive characteristic (Deligne-I.) at the light of relations recently discovered independently by Bhargav Bhatt and myself between cotangent complexes, de Rham-Witt, and derived de Rham complexes.

2019 Jun 13

# Annual conference of the Israel Mathematical Union 2019

9:00am to 7:00pm

### Program and Schedule (IMU website)

• Plenary morning session - Manchester Building, Hall 2.
• Parallel afternoon sessions - Sprinzak Building.
• Poster session - The Israel Institute for Advanced Studies building lobby.
2019 Jun 06

# Groups and dynamics seminar - Yoav Gat (Technion) - Counting lattice points on the Heisenberg groups - A generalization of a classical problem to a non-commutative setting

10:00am to 11:00am

Abstract: In this talk, I shall present a generalization of the lattice point counting problem for Euclidean balls in the context of a certain type of homogeneous groups, the so-called Heisenberg groups.
2019 Jun 13

# No seminar (IMU annual meeting)

10:00am to 11:10am

Abstract: A Markov chain over a finite state space is said to exhibit the total variation cutoff phenomenon if, starting from some Dirac measure, the total variation distance to the stationary distribution drops abruptly from near maximal to near zero. It is conjectured that simple random walks on the family of $k$-regular, transitive graphs with a two sided $\epsilon$ spectral gap exhibit total variation cutoff (for any fixed $k$ and \$\epsilon). This is known to be true only in a small number of cases.
2019 Jun 20

# Groups & dynamics seminar: Noam Kolodner (HUJI) - Surjectivity of morphisms of labeled core-graph under the action of automorphisms of a free group

10:00am to 11:00am

For a finitely generated subgroup H of the free group F_r, the Stallings graph of H is a finite combinatorial graph, whose edges are labeled by r letters (and their inverses), so that paths in the graphs correspond precisely to the words in H. Furthermore, there is a map between the graphs of two subgroups H and J, precisely when one is a subgroups of the other. Stallings theory studies the algebraic information which is encoded in the combinatorics of these graphs and maps.
2019 Jun 04

2:00pm to 3:00pm

2019 May 07

# Dynamics Lunch: Adi Weller "" Bouncing ball modes and quantum chaos " following Burq and Zworski

12:00pm to 1:00pm

2019 May 15

# Tzafriri lecture: Amir Algom - A simultaneous version of Host's equidistribution Theorem

4:00pm to 5:00pm

## Location:

Manchester Building (Hall 2), Hebrew University Jerusalem
Abstract:
2019 Apr 15

# NT & AG Lunch: Yakov Varshavsky "Geometric class field theory"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building
In a series of 2 talks I will try to explain that in the function field case the unramified global class
field theory has a simple geometric interpretation and a conceptual proof. We will only consider the unramified case (see, for example, https://arxiv.org/pdf/1507.00104.pdf or https://dspace.library.uu.nl/handle/1874/206061)
Key words: Abel-Jacobi map, l-adic sheaves, sheaf-function correspondence.
2019 Apr 29

# NT & AG Lunch: Yakov Varshavsky "Geometric class field theory, II"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

Geometric class field theory is an analog of the classical class field theory over function fields in which functions are replaced by sheaves. In the first part of my talk, I will formulate the result and explain its proof over C (the field of complex numbers).

In the  second part of the talk, I will try to outline the proof in the case of finite fields and indicate how this result implies the classical unramified global class field theory over function fields.

Most of the talk will be independent of the first one.
2019 Jun 18

# Dynamics Lunch: Matan Tal " Construction of a random walk on a lattice that is asymptotically appropriate for the ambient group (SLn(R))."

12:00pm to 1:00pm

The talk will be based on work done by Furstenberg, taken mainly from his paper "Randon Walks and Discrete Subgroups of Lie Groups". We will present the idea of a boundary attached to a random walk on a group, and explain intuitively how it can be applied to prove that SL2(R) and SLn(R) - for n greater than 2 - do not have isomorphic lattices. Then we focus on a key step in that proof: Constructing a random walk on a lattice in SLn(R) that has the same boundary as a "spherical" random walk on SLn(R) itself.
2019 May 20

# Landau Lecture 2: Old and new on the de Rham-Witt complex (NT - AG Seminar)

## Lecturer:

Prof. Luc Illusie (Université Paris-Sud)
2:30pm to 3:30pm

## Location:

Ross 70

### Old and new on the de Rham-Witt complex

Abstract: After reviewing the definition and the basic properties of the de Rham-Witt complex for smooth schemes over a perfect field, I will discuss the new approach to the subject developed by Bhatt, Lurie and Mathew.

I will explain the main results and sketch work in progress on the problems raised by this theory.

2019 Apr 11

# Groups & Dynamics Seminar: Erez Nesharim (Technion) - The t-adic Littlewood conjecture is false

10:00am to 11:00am

## Location:

Ross 70
The Littlewood and the p-adic Littlewood conjectures are famous open problems on the border between number theory and dynamics. In a joint work with Faustin Adiceam and Fred Lunnon we show that the analogue of the p-adic Littlewood conjecture over \mathbb{F}_3((1/t)) is false. The counterexample is given by the Laurent series whose coefficients are the regular paper folding sequence, and the method of proof is by reduction to the non vanishing of certain Hankel determinants.
2019 Apr 08

# NT & AG Seminar - Daniel Disegni

2:30pm to 3:30pm

## Location:

Ross 70A

Title: p-adic equidistribution of CM points on modular curves
Abstract: Let X be a modular curve. It is a curve over the integers, whose complex points form a quotient of the upper half-plane by a subgroup of SL(2,Z). In X there is a natural supply of algebraic points called CM points. After an idea of Heegner, they can be used to construct rational points on elliptic curves.
2019 May 02

# Kobi Peterzil (Haifa) - Closure of o-minimal flows on nilmanifolds

10:00am to 11:00am

I will discuss joint work with S. Starchenko, which combines dynamical systems in the nilmanifold setting with definable objects in o-minimal structures (e.g. semi-algebraic sets): Let G be a real algebraic unipotent group and let L be a lattice in G with p:G->G/L the quotient map. Given a subset X of G which is semi-algerbaic, or more generally definable in an o-minimal structure, we describe the closure of p(X) in terms of finitely many definable families of cosets of positive dimensional algebraic subgroups of G.