2019
Mar
26

# Events & Seminars

2019
May
14

# Dynamics Seminar: Rene Ruhr (Technion) Counting Saddle Connection on Translation surfaces.

2:00pm to 3:00pm

Abstract:

A collection of polygons with the property that to each side one can find another side parallel to it can be endowed with a translation surface structure by glueing along those edges.

This means that the closed surfaces obtained carries a flat metric outside finitely many conical singularities. Geodesics (which are straight lines) connecting such singularities are called saddle connections.

2019
Apr
30

# Dynamics Seminar: Iftach Dayan (TAU) "Random walks on the 1-dim torus and an application to normal numbers on fractals"

2:15pm to 3:15pm

## Location:

Ross 70

Abstract: We show that under certain conditions, a random walk on the 1-dim torus by affine expanding maps has a unique stationary measure. We then use this result to show that given an IFS of contracting similarity maps of the real line with a uniform contraction ratio 1/D, where D is some integer > 1, under some suitable condition, almost every point in the attractor of the given IFS (w.r.t. a natural measure) is normal to base D.

2019
Mar
20

# Set Theory Seminar - Tom Benhamou (TAU) (part II)

2:00pm to 3:30pm

## Location:

Ross 63

Title: Projections of Tree-Prikry forcing.

Abstract:

Gitik, Kanovei and Koepke proved that if U is a normal measure over \kappa then the projections of Prikry forcing with U is essentially Prikry forcing with U.

The questions remains regarding to the Tree-Prikry forcing. Gitik and B. showed that without normality, it is possible that a Tree-Prikry generic sequence adds a Add(\kappa,1)

generic function.

In this talk we wish to examine which forcing notions can be projections of Tree-Prikry forcing under different large cardinals assumptions.

2019
May
01

# Set Theory Seminar - Thomas Gilton (UCLA): Abraham-Rubin-Shelah Open Coloring Axiom with a large continuum

2:00pm to 3:30pm

## Location:

Ross 63

**Abstract**: In their 1985 paper, the above three authors introduced a consistent generalization of Ramsey's theorem to pairs of countable ordinals, which we abbreviate as $OCA_{ARS}$. This axiom asserts that for any continuous coloring (with respect to an appropriate topology) of pairs of countable ordinals, there is a decomposition of $\omega_1$ into countably-many homogeneous sets. The key to their argument is to construct Preassignments of Colors.

2019
Mar
13

# Set Theory Seminar - Tom Benhamou (TAU), "Projections of Tree-Prikry forcing"

2:00pm to 3:30pm

## Location:

Ross 63

Title: Projections of Tree-Prikry forcing.

Abstract:

Gitik, Kanovei and Koepke proved that if U is a normal measure over \kappa then the projections of Prikry forcing with U is essentially Prikry forcing with U.

The questions remains regarding to the Tree-Prikry forcing. Gitik and B. showed that without normality, it is possible that a Tree-Prikry generic sequence adds a Add(\kappa,1)

generic function.

In this talk we wish to examine which forcing notions can be projections of Tree-Prikry forcing under different large cardinals assumptions.

2019
Mar
27

# Set Theory Seminar - Ralf Schindler (Munster), "Paradoxical" sets with no well-ordering of the reals

2:00pm to 3:30pm

## Location:

Ross 63

Title: "Paradoxical" sets with no well-ordering of the reals

Abstract: By a Hamel basis we mean a basis for the reals, R, construed as a vecor space over

the field of rationals. In 1905, G. Hamel constructed such a basis from a well-ordering

of R. In 1975, D. Pincus and K. Prikry asked "whether a Hamel basis exists in any

model in which R cannot be well ordered." About two years ago, we answered this positively

in a joint paper with M. Beriashvili, L. Wu, and L. Yu. In more recent joint

Abstract: By a Hamel basis we mean a basis for the reals, R, construed as a vecor space over

the field of rationals. In 1905, G. Hamel constructed such a basis from a well-ordering

of R. In 1975, D. Pincus and K. Prikry asked "whether a Hamel basis exists in any

model in which R cannot be well ordered." About two years ago, we answered this positively

in a joint paper with M. Beriashvili, L. Wu, and L. Yu. In more recent joint

2019
Mar
19

# Dynamics lunch: Jing Zhou "“escaping orbit of some piecewise smooth Fermi acceleration model”

12:00pm to 1:00pm

## Location:

Manchester faculty club

Following "Dynamics of some piecewise smooth Fermi-Ulam Models” by De Simoi and Dolgopyat.

2019
Mar
12

# Dynamics Seminar: Terry Soo (KU) Finitary isomorphism of Bernoulli flows

2:15pm to 3:15pm

## Location:

Ross 70

A powerful theory due to Ornstein and his collaborators has been successfully applied to many random systems to show that they are isomorphic to independent and identically distributed systems. The isomorphisms provided by Ornstein's theory may not be finitary, that is, effectively realizable in practice. Despite the large number of systems known to be Bernoulli, there are only a handful of cases where explicit finitary isomorphisms have been constructed. In this talk, we will discuss classical and recent constructions, and some long standing open problems.

2019
Apr
10

# Special Analysis Seminar: Dirk Hundertmark (Karlsruhe) "Cwikel's bound reloaded"

2:30pm to 3:30pm

## Location:

Sprinzak 24

Title: Cwikel's bound reloaded

Abstract: There are a couple of proofs by now for the famous Cwikel--Lieb--Rozenblum (CLR) bound, which is a semiclassical bound on the number of bound states for a Schr\"odinger operator, proven in the 1970s.

Abstract: There are a couple of proofs by now for the famous Cwikel--Lieb--Rozenblum (CLR) bound, which is a semiclassical bound on the number of bound states for a Schr\"odinger operator, proven in the 1970s.

2019
Jun
19

# Analysis Seminar: Daniel Ofner (HUJI) "Mesoscopic universality for orthogonal polynomial ensembles on the unit circle"

12:00pm to 1:00pm

## Location:

Ross 70

Title: Mesoscopic universality for orthogonal polynomial ensembles on the unit circle

2019
May
22

# Analysis seminar: Yoel Grinshpon "Fluctuations of linear statistics for Schroedinger operators with a random decaying potential"

12:00pm to 1:00pm

## Location:

Ross 70

Title:

Fluctuations of linear statistics for Schroedinger operators with a random

decaying potential

Abstract:

Linear statistics provide a tool for the analysis of fluctuations of random

measures and have been extensively studied for various models in random

matrix theory. In this talk we discuss the application of the same

philosophy to the analysis of the finite volume eigenvalue counting measure

of one dimensional Schroedinger operators and demonstrate it with some

interesting results in the case of a random decaying potential.

Fluctuations of linear statistics for Schroedinger operators with a random

decaying potential

Abstract:

Linear statistics provide a tool for the analysis of fluctuations of random

measures and have been extensively studied for various models in random

matrix theory. In this talk we discuss the application of the same

philosophy to the analysis of the finite volume eigenvalue counting measure

of one dimensional Schroedinger operators and demonstrate it with some

interesting results in the case of a random decaying potential.

2019
Mar
13

# Analysis Seminar: Yehuda Pinchover (Technion) "How large can Hardy-weight be?"

12:00pm to 1:00pm

## Location:

Ross 70

Title: How large can Hardy-weight be?

Abstract: In the first part of the talk we will discuss the existence of optimal Hardy-type inequalities with 'as large as possible' Hardy-weight for a general second-order elliptic operator defined

on a noncompact Riemannian manifold, while the second part of the talk will be devoted to a sharp answer to the question: "How large can Hardy-weight be?"

Abstract: In the first part of the talk we will discuss the existence of optimal Hardy-type inequalities with 'as large as possible' Hardy-weight for a general second-order elliptic operator defined

on a noncompact Riemannian manifold, while the second part of the talk will be devoted to a sharp answer to the question: "How large can Hardy-weight be?"

2019
Feb
07

# Special group actions seminar. On Tame Subgroups of Finitely Presented Groups: Prof. Rita Gitik, University of Michigan, Ann Arbor.

10:00am to 11:00am

## Location:

Ross 70

We describe several examples of tame subgroups of finitely

presented groups and prove that the fundamental groups of certain finite

graphs of groups are locally tame.

presented groups and prove that the fundamental groups of certain finite

graphs of groups are locally tame.

2019
Jan
23

# T&G: Sylvain Cappell (NYU), Atiyah-Bott classes and extending representations of fundamental groups of 3-manifolds from part of the boundary

1:00pm to 2:00pm

## Location:

Room 70, Ross Building, Jerusalem, Israel

We consider the problem of extending a representation of the fundamental group of 3-manifolds from part of the boundary surfaces. Applications to links will be discussed. Combining this with some cohomology classes of Atiyah and Bott leads to new multivariable polynomial invariants of 3-manifolds with boundary.

This is joint work with Edward Miller.

No background in 3-dimensional topology will be assumed in this survey and research talk.

This is joint work with Edward Miller.

No background in 3-dimensional topology will be assumed in this survey and research talk.