2019 Jun 12

# NO SEMINAR Basic Notions

4:00pm to 5:15pm

## Location:

Ross 70
1) Abstract of Wayne's part: Today, in our modern world, we perceive the physical universe in mathematical terms; whether degrees on longitude and latitude on earth, or in units of space-time beyond our earthly horizons. This talk will present two ancient cuneiform tablets from Babylonia which offer a geometric impression of the physical world as experienced by ancient Babylonians. Comparisons will be made with a range of other ancient mathematical, geographic, and astronomical materials from the cuneiform Ancient Near East. 2) Abstract of Mourtaza's part:
2019 Jun 02

# Logic Seminar - Javier de la Nuez Gonzalez

1:00pm to 3:00pm

## Location:

Shprinzak 29
Minimal and non-minimal automorphism groups of homogeneous structures

A Hausdorff topological group G is said minimal if G does not admit any strictly coarser Hausdorff group topology.

Examples include the isometry group of the Urysohn sphere, due to Uspenskij, and Aut(M) for M stable and w-categorical, a deep fact due to Ben Yacov and Tsankov.
2019 Jun 12

3:00pm to 4:00pm

2019 Jun 03

# פגישה עם ורה ודיאנה

9:30am to 10:30am

2019 Jun 11

# Dynamics Lunch: Yotam Smilansky "The space of quasicrystals."

12:00pm to 1:00pm

Abstract: Cut and project point sets are defined by identifying a strip of a fixed n-dimensional lattice (the "cut"), and projecting the lattice points in that strip to a d-dimensional subspace (the "project"). Such sets have a rich history in the study of mathematical models of quasicrystals, and include well known examples such as the Fibonacci chain and vertex sets of Penrose tilings.
2019 Jun 04

# Groups & dynamics seminar: Arie Levit(Yale) - Surface groups are flexibly stable

12:00pm to 1:00pm

Abstract:
A group G is stable in permutations if every almost-action of G on a finite set is close to some actual action. Part of the interest in this notion comes from the observation that a non-residually finite stable group cannot be sofic.
I will show that surface groups are stable in a flexible sense, that is if one is allowed to "add a few extra points" to the action. This is the first non-trivial stability result for a non-amenable group.
2019 Jun 03

# NT & AG Seminar: Shuddhodan K V (HUJI) "Self maps of varieties over finite fields"

2:30pm to 3:30pm

## Location:

Ross building 70
Title: Title: Self maps of varieties over finite fields
Abstract: Esnault and Srinivas proved that as in Betti cohomology over the complex numbers, the value of the entropy of an automorphism of a smooth proper surface over a finite field $\F_q$ is taken in the subspace spanned by algebraic cycles inside $\ell$-adic cohomology. In this talk we will discuss some analogous questions in higher dimensions motivated by their results and techniques.
2019 May 30

# Basic Notions: Eugene Trubowitz (ETH) "Mathematical Methods of Many Body Quantum Field Theory"

4:00pm to 5:15pm

## Location:

Ross 70
Let (V,<, >) be a finite dimensional inner product space and K a self adjoint element of End(V ). It is an axiom of physics that the expected value of A in End(V ) in equilibrium at temperature T with respect to K is
the ration Tr(A exp (-K/T))/Tr(exp (-K/T)).
2019 Jun 06

# Basic Notions: Eugene Trubowitz (ETH) "Mathematical Methods of Many Body Quantum Field Theory"

4:00pm to 5:15pm

## Location:

Ross 70
Let (V,<, >) be a finite dimensional inner product space and K a self adjoint element of End(V ). It is an axiom of physics that the expected value of A in End(V ) in equilibrium at temperature T with respect to K is
the ration Tr(A exp (-K/T))/Tr(exp (-K/T)).
2019 May 21

# Special groups theory seminar: Abdalrazzaq R A Zalloum (Suny Buffalo) "Regular languages for hyperbolic-like geodesics".

4:00pm to 5:00pm

## Location:

Ross 63
Combinatorial group theory began with Dehn's study of surface
groups, where he used arguments from hyperbolic geometry to solve the
word/conjugacy problems. In 1984, Cannon generalized those ideas to all
"hyperbolic groups", where he was able to give a solution to the
word/conjugacy problem, and to show that their growth function satisfies
a finite linear recursion. The key observation that led to his
discoveries is that the global geometry of a hyperbolic group is determined locally:
2019 May 21

# Special groups theory seminar: Abdalrazzaq R A Zalloum (Suny Buffalo) "Regular languages for hyperbolic-like geodesics".

4:00pm to 5:00pm

## Location:

Ross 63
Combinatorial group theory began with Dehn's study of surface groups, where he used arguments from hyperbolic geometry to solve the word/conjugacy problems. In 1984, Cannon generalized those ideas to all "hyperbolic groups", where he was able to give a solution to the word/conjugacy problem, and to show that their growth function satisfies a finite linear recursion. The key observation that led to his discoveries is that the global geometry of a hyperbolic group is determined locally: first, one discovers the local picture of G, then the recursive structure
2019 May 28

# Dynamics Lunch: Uri Gabor ״Percolation on finite graphs and isoperimetric inequalities" of Alon, Benjamini and Stacey (2004)״

12:00pm to 1:00pm

Following the paper “ Preperiodic points and unlikely intersection” by Baker and DeMarco.
2019 Jun 25

# Dynamics Lunch: Michael Chapman ״Markoff triples״

12:00pm to 1:00pm

Partially based on the paper "The Markoff Group of Transformations in Prime and Composite Moduli" by Meiri and Puder.
2019 Jun 03

# NT & AG Lunch: Michael Temkin "The explicit local class field theory"

1:00pm to 2:00pm

## Location:

Faculty lounge, Math building

I'll tell a couple of anecdotes related to imaginary quadratic fields
(e.g. primes in the sequence n^2+n+41), and then open a new story --
local CFT and the explicit construction of K^ab due to Lubin-Tate.
2019 Jun 04

# Dynamics Seminar: Arie Levit - Surface groups are flexibly stable

12:00pm to 1:00pm

This will be a research talk. The abstract is below:
A group G is stable in permutations if every almost-action of G on a finite set is close to some actual action. Part of the interest in this notion comes from the observation that a non-residually finite stable group cannot be sofic.
I will show that surface groups are stable in a flexible sense, that is if one is allowed to "add a few extra points" to the action. This is the first non-trivial stability result for a non-amenable group.