2019
Jun
12

# פגישה עם תומאס ויוהאנס

3:00pm to 4:00pm

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2019
Jun
12

3:00pm to 4:00pm

2019
Jun
11

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

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.

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

2:30pm to 3:30pm

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.

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

4:00pm to 5:15pm

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)).

the ration Tr(A exp (-K/T))/Tr(exp (-K/T)).

2019
Jun
06

4:00pm to 5:15pm

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)).

the ration Tr(A exp (-K/T))/Tr(exp (-K/T)).

2019
May
21

4:00pm to 5:00pm

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:

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

4:00pm to 5:00pm

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

12:00pm to 1:00pm

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

2019
Jun
25

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

1:00pm to 2:00pm

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

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.

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
May
21

11:00am to 12:30pm

Room 07, Levi Building, Jerusalem, Israel

I will give an introduction to sheaves and microlocal sheaves, as pioneered by Kashiwara-Schapira. The goal will be to explain recent work with Shende establishing that microlocal sheaves on a Weinstein manifold are a symplectic invariant.

2019
Jun
11

2:00pm to 3:00pm

Abstract. We consider families of holomorphic maps defined on subsets of the complex plane,

2019
May
13