2016
Feb
17

# Menachem Magidor 70th Birthday Conference

Wed, 17/02/2016 (All day) to Fri, 19/02/2016 (All day)

2016
Feb
17

Wed, 17/02/2016 (All day) to Fri, 19/02/2016 (All day)

2016
Mar
31

10:00am to 11:00am

Ross building, Hebrew University of Jerusalem, (Room 70)

To every topological group, one can associate a unique universal

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

2016
Dec
01

10:30am to 11:30am

Ross 70

INTRODUCTION TO MEAN DIMENSION AND THE EMBEDDING PROBLEM OF DYNAMICAL SYSTEMS (Part 1)

2016
Nov
24

10:30am to 11:30am

Ross 70

Speaker: Oren Becker

Title: Locally testable groups

Abstract:

Arzhantseva and Paunescu [AP2015] showed that if two permutations X and Y in Sym(n) nearly commute (i.e. XY is close to YX), then the pair (X,Y) is close to a pair of permutations that really commute.

Title: Locally testable groups

Abstract:

Arzhantseva and Paunescu [AP2015] showed that if two permutations X and Y in Sym(n) nearly commute (i.e. XY is close to YX), then the pair (X,Y) is close to a pair of permutations that really commute.

2016
Dec
22

2016
Jan
07

10:00am to 11:00am

Ross building, Hebrew University of Jerusalem, (Room 70)

To every topological group, one can associate a unique universal

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

2016
Dec
08

2016
Dec
29

2016
Mar
03

10:00am to 11:00am

Ross building, Hebrew University of Jerusalem, (Room 70)

To every topological group, one can associate a unique universal

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

2016
Nov
17

10:30am to 11:30am

Ross 70

Speaker: Arie Levit

Weizmann Institute

Title: Local rigidity of uniform lattices

Abstract: A lattice is topologically locally rigid (t.l.r) if small deformations of it are isomorphic lattices. Uniform lattices in Lie groups were shown to be t.l.r by Weil [60']. We show that uniform lattices are t.l.r in any compactly generated topological group.

Weizmann Institute

Title: Local rigidity of uniform lattices

Abstract: A lattice is topologically locally rigid (t.l.r) if small deformations of it are isomorphic lattices. Uniform lattices in Lie groups were shown to be t.l.r by Weil [60']. We show that uniform lattices are t.l.r in any compactly generated topological group.

2016
Dec
15

10:30am to 11:30am

Ross 70

Abstract:

In this talk I'll present a joint work with Ariel Yadin, in which we solve the Furstenberg Entropy Realization Problem for finitely supported random walks (finite range jumps) on free groups and lamplighter groups. This generalizes a previous result of Bowen. The proof consists of several reductions which have geometric and probabilistic flavors of independent interests.

All notions will be explained in the talk, no prior knowledge of Invariant Random Subgroups or Furstenberg Entropy is assumed.

In this talk I'll present a joint work with Ariel Yadin, in which we solve the Furstenberg Entropy Realization Problem for finitely supported random walks (finite range jumps) on free groups and lamplighter groups. This generalizes a previous result of Bowen. The proof consists of several reductions which have geometric and probabilistic flavors of independent interests.

All notions will be explained in the talk, no prior knowledge of Invariant Random Subgroups or Furstenberg Entropy is assumed.

2015
Dec
31

10:00am to 11:00am

Ross building, Hebrew University of Jerusalem, (Room 70)

minimal flow (UMF): a flow that maps onto every minimal flow of the

group. For some groups (for example, the locally compact ones), this

flow is not metrizable and does not admit a concrete description.

However, for many "large" Polish groups, the UMF is metrizable, can be

computed, and carries interesting combinatorial information. The talk

will concentrate on some new results that give a characterization of

metrizable UMFs of Polish groups. It is based on two papers, one joint

2015
Nov
24

2:00pm to 3:00pm

Manchester building, Hebrew University of Jerusalem, (Room 209)

The Danzer problem and a solution to a related problem of Gowers

Is there a point set Y in R^d, and C>0, such that every convex

set of volume 1 contains at least one point of Y and at most C? This

discrete geometry problem was posed by Gowers in 2000, and it is a special

case of an open problem posed by Danzer in 1965. I will present two proofs

that answers Gowers' question with a NO. The first approach is dynamical;

we introduce a dynamical system and classify its minimal subsystems. This

Is there a point set Y in R^d, and C>0, such that every convex

set of volume 1 contains at least one point of Y and at most C? This

discrete geometry problem was posed by Gowers in 2000, and it is a special

case of an open problem posed by Danzer in 1965. I will present two proofs

that answers Gowers' question with a NO. The first approach is dynamical;

we introduce a dynamical system and classify its minimal subsystems. This

2015
Dec
02

2:00pm to 3:00pm

Ross 70

Title: Local limit theorem for certain ballistic random walks in random

environments

Abstract: We study the model of random walks in random environments in

dimension four and higher under Sznitman's ballisticity condition (T').

We prove a version of a local Central Limit Theorem for the model and also

the existence of an equivalent measure which is invariant with respect

to the point of view of the particle. This is a joint work with Noam Berger

and Moran Cohen.

environments

Abstract: We study the model of random walks in random environments in

dimension four and higher under Sznitman's ballisticity condition (T').

We prove a version of a local Central Limit Theorem for the model and also

the existence of an equivalent measure which is invariant with respect

to the point of view of the particle. This is a joint work with Noam Berger

and Moran Cohen.

2015
Nov
10

2:00pm to 3:00pm

Manchester building, Hebrew University of Jerusalem, (Room 209)

Title: Self-affine measures with equal Hausdorff and Lyapunov dimensions

Abstract:

Let μ be the stationary measure on ℝd which corresponds to a self-affine iterated function system Φ and a probability vector p. Denote by A⊂Gl(d,ℝ) the linear parts of Φ. Assuming the members of A contract by more than 12, it follows from a result by Jordan, Pollicott and Simon, that if the translations of Φ are drawn according to the Lebesgue measure, then dimHμ=min{D,d} almost surely. Here D is the Lyapunov dimension, which is an explicit constant defined in terms of A and p.

Abstract:

Let μ be the stationary measure on ℝd which corresponds to a self-affine iterated function system Φ and a probability vector p. Denote by A⊂Gl(d,ℝ) the linear parts of Φ. Assuming the members of A contract by more than 12, it follows from a result by Jordan, Pollicott and Simon, that if the translations of Φ are drawn according to the Lebesgue measure, then dimHμ=min{D,d} almost surely. Here D is the Lyapunov dimension, which is an explicit constant defined in terms of A and p.