2020
Mar
25

# Events & Seminars

2020
Jun
03

# Analysis Seminar: Victor Ivrii (Toronto) "Complete Spectral Asymptotics for Periodic and Almost Periodic Perturbations of Constant Coefficients Operators and Bethe-Sommerfeld Conjecture in Semiclassical Settings"

12:00pm to 1:00pm

## Location:

Ross 70

TITLE:

Complete Spectral Asymptotics for Periodic and Almost Periodic Perturbations of Constant Coefficients Operators and Bethe-Sommerfeld Conjecture in Semiclassical Settings

ABSTRACT:

Under certain assumptions, we derive a complete semiclassical asymptotics of aspectral function of the constant coecient scalar operator perturbed by almostperiodic smaller operator. In particular, a com-

plete semiclassical asymptotics of the integrated density of states also holds.

Complete Spectral Asymptotics for Periodic and Almost Periodic Perturbations of Constant Coefficients Operators and Bethe-Sommerfeld Conjecture in Semiclassical Settings

ABSTRACT:

Under certain assumptions, we derive a complete semiclassical asymptotics of aspectral function of the constant coecient scalar operator perturbed by almostperiodic smaller operator. In particular, a com-

plete semiclassical asymptotics of the integrated density of states also holds.

2020
Jan
29

# Logic Seminar - Yatir Halevi

9:45am to 11:45am

## Location:

Ross building - Room 63

**Yatir Halevi**will speal about

**Coloring Stable Graphs**.

Title: Coloring Stable Graphs

__Abstract:__Given a graph G=(V,E), a coloring of G in \kappa colors is a

map c:V\to \kappa in which adjacent vertices are colored in different

colors. The chromatic number of G is the smallest such \kappa.

We will briefly review some questions and conjectures on the chromatic

number of infinite graphs and will mainly concentrate on the strong

form of Taylor's conjecture:

2020
Jan
26

2020
Jan
22

# Logic Seminar - Yuval Dor

11:00am to 1:00pm

## Location:

Ross building - Room 63

**Yuval Dor**will speal about

**Transformal Valued Fields**.

__Abstract__

**:**Abraham Robinson characterized the existentially closed valued fields as those which are algebraically closed and nontrivially valued. This theorem is somewhat surprising: it makes no assumption on the topology of the field other than the fact that it is not discrete, and immediately implies a strong from of the Nullstellensatz, asserting that the only obstruction to the solvability of a system of polynomial equations in a neighborhood of a point is the obvious one.

2020
Jan
30

# Groups & Dynamics Seminar. Chloe Perin (HUJI): Homogeneity of torsion-free hyperbolic groups

10:00am to 11:00am

## Location:

Ross 70 a

A countable group is said to be homogeneous if whenever tuples of elements u, v satisfy the same first-order formulas there is an automorphism of the group sending one to the other. We had previously proved with Rizos Sklinos that free groups are homogeneous, while most surface groups aren't. In a joint work with Ayala Dente-Byron, we extend this to give a complete characterization of torsion-free hyperbolic groups that are homogeneous.

2020
Jan
22

# Grad student seminar - Barak Ohana - Bass-Serre theory

4:00pm to 5:00pm

2020
Jan
22

2020
Mar
16

# NT Seminar - Sam Chow - CANCELLED!!!

2:30pm to 3:30pm

## Location:

Ross 70

**Title.**Dyadic approximation in the Cantor set

**Abstract.**We investigate the approximation rate of a typical element of the Cantor set by dyadic rationals. This is a manifestation of the times two times three phenomenon, and is joint work with Demi Allen and Han Yu.

2020
Apr
01

2020
Mar
23

# NT Seminar - TBA

(All day)

2020
Jan
19

# Game theory seminar: Computational Design Principles of Cognition (Yuval Hart)

2:00pm to 3:00pm

## Location:

Elath Hall, 2nd floor, Feldman Building

Driven by recent technological advancements, behavior and brain activity can now be measured at an unprecedented resolution and scale. This “big-data” revolution is akin to a similar revolution in biology. In biology, the wealth of data allowed systems-biologists to uncover the underlying design principles that are shared among biological systems. In my studies, I apply design principles from systems-biology to cognitive phenomena. In my talk I will demonstrate this approach in regard to creative search.

2020
Jan
14

# T&G: Pavel Etingof (MIT), Short star-products for filtered quantizations

1:00pm to 2:30pm

## Location:

Room 209, Manchester Building, Jerusalem

Motivated by three-dimensional N=4 superconformal field theory, in 2016 Beem, Peelaers and Rastelli considered short even star-products for homogeneous symplectic singularities (more precisely, hyper-Kahler cones) and conjectured that they exist and depend on finitely many parameters. We prove the dependence on finitely many parameters in general and existence for a large class of examples, using the connection of this problem with zeroth Hochschild homology of quantizations suggested by Kontsevich.

2020
Jan
28

# Special Talk: Rita Gitik (University of Michigan) : "Geodesic triangles in the hyperbolic plane."

11:00am to 12:00pm

## Location:

Ross 70

Let M be an orientable hyperbolic surface without boundaryand let c be a closed geodesic in M.

We prove that any side of any triangle formed by distinctlifts of c in the hyperbolic plane is shorter than c.

The talk will be presented for advanced undergraduate andbeginning graduate students

2020
Jan
30

# Basic Notions: Cy Maor (HUJI) "Infinite dimensional Riemannian geometry in hydrodynamics and shape analysis".

4:00pm to 5:15pm

## Location:

Ross 70

In the mid-18th century,Euler derived his famous equations of motion of an incompressible fluid, one ofthe most studied equations in hydrodynamics. More than 200 years later, in1966, Arnold observed that they are, in fact, geodesic equations on the(infinite dimensional) Lie group of volume-preserving diffeomorphisms of amanifold, endowed with a certain right-invariant Riemannian metric.