2019
May
01

# Events & Seminars

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.

2019
Jun
05

# Logic Seminar - Oren Kalish

11:00am to 1:00pm

## Location:

Ross 63

**Tight weakly o-minimal structures**

We introduce a class of weakly o-minimal expansions of groups, called tight structures. We prove that the o-minimal completion of a tight structure is linearly bounded.

2019
May
22

# Logic Seminar - Shahar Oriel

11:00am to 1:00pm

## Location:

Ross 63

**An omega-categorical strictly stable pseudo-plane**

Lachlan conjectured that any omega-categorical stable theory is even omega-stable. Later in 1980 it was shown that there is no omega-categorical omega-stable pseudo plane. In 1988, Hrushovski refuted Lachlan's conjecture by constructing an omega-categorical, strictly stable pseudo-plane.

We will give a quick overview of the construction and try to use this example to test if some properties of omega-categorical omega-stable theories lift to omega-categorical stable theories.

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
18

# Special course: A. Goncharov (Yale, visiting Einstein Institute of Mathematics) "Quantum geometry of moduli spaces of local systems on surfaces and representation theory"

Repeats every week every Monday until Mon Apr 29 2019 except Mon Apr 22 2019.

4:00pm to 6:00pm4:00pm to 6:00pm

4:00pm to 6:00pm

4:00pm to 6:00pm

4:00pm to 6:00pm

4:00pm to 6:00pm

## Location:

Ross 70

Abstract. This is a joint work with Linhui Shen.

A decorated surface is an oriented surface with punctures and a finite collection of special points on the boundary, considered modulo isotopy.

Let G be a split adjoint group. We introduce a moduli space Loc(G,S) of G-local systems on a decorated surface S, which reduces to the character variety when S has no boundary, and quantize it.

2019
Mar
18

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

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.

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
Apr
02

2019
Mar
18

# NT & AG - Antoine Ducros (Sorbonne Université), "Non-standard analysis and non-archimedean geometry"

2:30pm to 3:30pm

## Location:

Room 70A, Ross Building, Jerusalem, Israel

There is a general slogan according to which the limit behaviour of a one-parameter family of complex algebraic varieties when the parameter t tends to zero should be (partially) encoded in the associated t-adic analytic space in the sense of Berkovich; this slogan has given rise to deep and fascinating conjecturs by Konsevich and Soibelman, as well as positive results by various authors (Berkovich, Nicaise, Boucksom, Jonsson...).

2019
Mar
13

2019
May
15

# Set Theory Seminar - Gabriel Fernandes (BIU): Local core models with more Woodin cardinals

2:00pm to 3:30pm

## Location:

Ross 63

Abstract: We combine a technique of Steel with one due to Jensen and Steel to

obtain a core model below singular cardinals kappa which are

sufficiently closed under the beth function, assuming that there is no

premouse of height kappa with unboundedly many Woodin cardinals.

The motivation for isolating such core model is computing a lower bound for the strength of

the theory: T = ''ZFC + there is a singular cardinal kappa such that the set of ordinals below kappa where GCH holds is stationary and co-stationary''.

obtain a core model below singular cardinals kappa which are

sufficiently closed under the beth function, assuming that there is no

premouse of height kappa with unboundedly many Woodin cardinals.

The motivation for isolating such core model is computing a lower bound for the strength of

the theory: T = ''ZFC + there is a singular cardinal kappa such that the set of ordinals below kappa where GCH holds is stationary and co-stationary''.

2019
May
22

# Set Theory Seminar - Gabriel Fernandes (BIU) (part II)

2:00pm to 3:30pm

## Location:

Ross 63

Abstract: We combine a technique of Steel with one due to Jensen and Steel to

obtain a core model below singular cardinals kappa which are

sufficiently closed under the beth function, assuming that there is no

premouse of height kappa with unboundedly many Woodin cardinals.

The motivation for isolating such core model is computing a lower bound for the strength of

the theory: T = ''ZFC + there is a singular cardinal kappa such that the set of ordinals below kappa where GCH holds is stationary and co-stationary''.

obtain a core model below singular cardinals kappa which are

sufficiently closed under the beth function, assuming that there is no

premouse of height kappa with unboundedly many Woodin cardinals.

The motivation for isolating such core model is computing a lower bound for the strength of

the theory: T = ''ZFC + there is a singular cardinal kappa such that the set of ordinals below kappa where GCH holds is stationary and co-stationary''.