Eventss

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 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,
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.
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 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 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.

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