2019
Jun
04

# Events & Seminars

2019
May
07

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.
P.S. Michael will continue his series of lectures on May 6.

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.

2019
Apr
04

2019
Apr
10

# Logic Seminar - Yatir Halevi

11:00am to 1:00pm

## Location:

Ross 63

**Type Definable Semigroups in Stable Structures**

A semigroup is a set together with an associative binary operation. As opposed to stable groups, the model theory of stable semigroups is not so rich. One reason for that is their abundance.

We will review (and prove) some known results on type-definable semigroups in stable structures and offer some examples and counter-examples.

2019
May
06

# NT & AG Lunch: Michael Temkin "Elliptic curves with complex multiplication"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

We'll talk about explicit class field theory of imaginary quadratic fields

2019
Apr
08

# NT & AG Lunch: Michael Temkin, "Explicit Class Field Theory"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

In a series of talks I will describe in the chronological order all cases where an explicit
construction of CFT is known:
0. The multiplicative group and Kronecker-Weber -- the case of Q.
1. Elliptic curves with complex multiplication and
Kronecker's Jugendraum -- the case of imaginary quadratic extensions.
2. Formal O-models of Lubin-Tate -- the local case.
3. Drinfeld's elliptic modules -- the function field case.
\infinity. Extending this to real quadratic fields and, more generally,
solving Hilbert's problem 12 will be left to the audience as an exercise.

2019
Apr
01

# NT & AG Lunch: Ehud DeShalit "An overview of class field theory, III"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

Class field theory classifies abelian extensions of local and global fields
in terms of groups constructed from the base. We shall survey the main results of class
field theory for number fields and function fields alike. The goal of these introductory lectures
is to prepare the ground for the study of explicit class field theory in the function field case,
via Drinfeld modules.
I will talk for the first 2 or 3 times.