# Activities This Week

## Colloquium

### First-order logic on the free group and geometry

*Dec 6, 14:30-15:30, 2016*,
**Math -101**

#### Speaker

**Chloé Perin** (*Hebrew University of Jerusalem*)

#### Abstract

We will give an overview of questions one might ask about the first-order theory of free groups and related groups: how much information can first-order formulas convey about these groups or their elements, what algebraic interpretation can be given for model theoretic notions such as forking independence, etc. It turns out that techniques from geometric group theory are very useful to tackle such problems. Some of these questions have been answered, others are still open - our aim is to give a feel for the techniques and directions of this field. We will assume no special knowledge of model theory.

## Algebraic Geometry and Number Theory

### The Derived Category of Sheaves of Commutative DG Rings

*Dec 7, 15:10-16:30, 2016*,
**Math -101**

#### Speaker

**Amnon Yekutieli** (*BGU*)

## Geometry and Group Theory

### Geometric Property (T)

*Dec 4, 14:30-15:30, 2016*,
**-101**

#### Speaker

**Kyle Austin** (*BGU*)

#### Abstract

One way of viewing coarse geometry is that it is the perfect tool for treating metric spaces like groups and doing representation theoretic/harmonic analytical techniques in a much larger setting. R. Willett and G. Yu define a property (T) for coarse spaces using the uniform Roe algebra. In this talk, I plan to define coarse spaces and show that the uniform Roe algebra is nice tool that acts like the group C* algebra. I will define geometric property (T) and discuss some of its properties.

## Probability and ergodic theory (PET)

### The geometry of locally infinite graphs

*Dec 6, 10:50-12:00, 2016*,
**Math -101**

#### Speaker

**Sebastien Martineau** (*Weizmann*)