2019
Mar
31

# Events & Seminars

2019
Apr
04

# Special talk : Prof. Efim Zelmanov (UCSD) : Growth Functions

## Lecturer:

Prof. Efim Zelmanov (UCSD)

12:00pm to 1:00pm

## Location:

Ross 70

We will discuss growth functions of algebras and monoids.

2019
Mar
26

# Dynamics Seminar: Nattalie Tamam "Diagonalizable groups with non-obvious divergent trajectories"

12:00pm to 1:00pm

## Location:

Manchester faculty club

Singular vectors are the ones for which Dirichlet’s theorem can be infinitely improved. For example, any rational vector is singular. The sequence of approximations for any rational vector q is 'obvious'; the tail of this sequence contains only q. In dimension one, the rational numbers are the only singulars. However, in higher dimensions there are additional singular vectors. By Dani's correspondence, the singular vectors are related to divergent trajectories in Homogeneous dynamical systems. A corresponding 'obvious' divergent trajectories can also be defined.

2019
Mar
28

# Basic Notions: Benjamin Weiss (HUJI) "Groups with property T have and "cost" of equivalence relations"

4:00pm to 5:15pm

## Location:

Ross 70

The cost of a measure-preserving equivalence relation is a quantitative measure of its complexity. I will
explain what the cost is and then discuss a recent result of Tom Hutchcroft and Gabor Pete in which they construct,
for any group with property T, a free ergodic measure preserving action with cost 1.

2019
Mar
25

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

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.

2019
Mar
26

# T&G: Vivek Shende (Berkeley), Quantum topology from symplectic geometry

1:00pm to 2:30pm

## Location:

Room 110, Manchester Building, Jerusalem, Israel

The discovery of the Jones polynomial in the early 80's was the beginning of ``quantum topology'': the introduction of various invariants which, in one sense or another, arise from quantum mechanics and quantum field theory. There are many mathematical constructions of these invariants, but they all share the defect of being first defined in terms of a knot diagram, and only subsequently shown by calculation to be independent of the presentation. As a consequence, the geometric meaning has been somewhat opaque.

2019
Apr
03

# Logic Seminar - Tomasz Rzepecki

11:00am to 1:00pm

## Location:

Ross 63

**G-compactness, hereditary G-compactness and related phenomena**

The notion of G-compactness, along with the Galois groups, was introduced by Lascar in order to find a sufficient condition under which a first order theory can be recovered from the category of its models.

I will recall this notion. In order to do that, I will also recall various classical notions of strong types, and possibly the Galois group of the theory (and briefly discuss their importance).

2019
Jun
26

# Logic Seminar - Nick Ramsey

11:00am to 1:00pm

## Location:

Ross 63

Possibilities for a theory of independence beyond NSOP_1 and NTP_2

2019
Mar
20

# Logic Seminar - Spencer Unger

11:00am to 1:00pm

## Location:

Ross 63

**Stationary reflection and the singular cardinals hypothesis.**

2019
Jun
19

# Logic Seminar - Shlomo Eshel

11:00am to 1:00pm

## Location:

Ross 63

**A generalization of the Szemeredi-Trotter theorem to o-minimal expansions of fields**

2019
May
29

2019
May
01

2019
May
15

# Logic Seminar - Shimon Garti

11:00am to 1:00pm

## Location:

Ross 63

**On the cofinality of some classical cardinal characteristics.**

We will try to prove two results about the possible cofinality of cardinal characteristics.

The first result is about the ultrafilter number, and this is a part of a joint work with Saharon Shelah.

The second is about Galvin's number, and this is a joint work with Yair Hayut, Haim Horowitz and Menachem Magidor.

2019
Mar
27

# Logic Seminar - Shlomo Eshel

11:00am to 1:00pm

## Location:

Ross 63

**Uniform definability of types over finite sets**

Uniform definability of types over finite sets (UDTFS) is a property of formulas which implies NIP and characterizes NIP in the level of theories (by Chernikov and Simon).

In this talk we will prove that if T is any theory with definable Skolem functions, then every dependent formula phi has UDTFS. This result can be seen as a translation of a result of Shay Moran and Amir Yehudayof in machine learning theory to the logical framework.

2019
Jun
12

# Logic Seminar - Moshe Illouz

11:00am to 1:00pm

## Location:

Ross 63

**Categoricity relative to order and order stability**

In this talk we will show a generalization of the notion of stability and categoricity relative to the order. One of the natural questions is whether categoricity implies stability, just like in the regular case. We will show that this is not true generally, by using a result of Pabion on peano arithmetic. We are also going to see some specific cases where categoricity relative to the order implies stability.