2019
Mar
20

# Logic Seminar - Spencer Unger

11:00am to 1:00pm

## Location:

Ross 63

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

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2019
Mar
20

11:00am to 1:00pm

Ross 63

2019
Jun
19

11:00am to 1:00pm

Ross 63

2019
May
29

2019
May
01

2019
May
15

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

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

11:00am to 1:00pm

Ross 63

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
Mar
18

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

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

1:00pm to 2:00pm

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
Apr
02

2019
Mar
18

2:30pm to 3:30pm

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

2:00pm to 3:30pm

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''.

2019
May
22

2:00pm to 3:30pm

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''.