2019
May
01

# Events & Seminars

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
work, additionally with J. Brendle and F. Castiblanco we constructed a model of

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
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

2019
Jun
19

2019
May
22

# Analysis seminar: Yoel Grinshpon

12:00pm to 1:00pm

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?"

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.

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.

2019
Mar
19

# Dynamics Seminar: Elon Lindenstrauss (HUJI) - Double variational principle for mean dimension

2:15pm to 3:15pm

Mean dimension is a topological invariant of dynamical systems introduced by Gromov that measures the number of parameters per iteration needed to describe a trajectory in the system. We characterize this invariant (at least for dynamical systems with the marker property, such as infinite minimal systems) using a min-max principle, where choices of both a metric on the topological space and an invariant probability measure on the system are varied.
The work I will report on is joint work with M. Tsukamoto.

2019
Jan
15

# T&G: Michael Khanevsky (Technion), Geometry of sets of Hamiltonian isotopic curves in a symplectic surface

2:00pm to 3:30pm

## Location:

Room 209, Manchester Building, Jerusalem, Israel

Given two Hamiltonian isotopic curves in a surface, one would like to tell whether they are "close" or "far apart". A natural way to do that is to consider Hofer's metric which computes mechanical energy needed to deform one curve into the other. However due to lack of tools the large-scale Hofer geometry is only partially understood. On some surfaces (e.g. S^2) literally nothing is known.

2019
May
15