2020 Jan 23

Groups & Dynamics Seminar. POSTPONED

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 05

Game theory seminar: Monotonic Norms and Orthogonal Issues in Multidimensional Voting (Benny Moldovanu)

2:00pm to 3:00pm

Location:

Elath Hall, 2nd floor, Feldman Building
We study issue-by-issue voting and robust mechanism design in multidimensional frameworks where privately informed agents
have preferences induced by general norms. We uncover the deep connections between dominant strategy incentive compatibility (DIC) on the one hand,
and several geometric/functional analytic concepts on the other. Our main results are:
1) Marginal medians are DIC if and only if they are calculated
with respect to coordinates defined by a basis such that the norm is orthant-monotonic in the associated coordinate system.
2020 Jan 01

Logic Seminar - Spencer Unger

11:00am to 1:00pm

Location:

Ross building - Room 63
2020 May 14

Colloquium: Henri Berestycki (EHESS)

2:30pm to 3:30pm

Location:

Manchester Building (Hall 2), Hebrew University Jerusalem
2020 Mar 18

Analysis Seminar: Cancelled

12:00pm to 1:00pm

Location:

Ross 70
Abstract:

Weprove eigenfunction and quasimode estimates on compact Riemannian manifolds for Schr\”odingeroperators, $H_V=-\Delta_g+V$ involving critically singular potentials $V$ which weassume tobe in $L^{n/2}$ and/or the Kato class ${\mathcal K}$.  Our proof is basedon modifying the oscillatory integral/resolvent approachthat was used to study the case where $V \equiv 0$ using recently developedtechniques by many authorsto study variable coefficient analogs of the uniform Sobolev estimates ofKenig, Ruiz and the speaker.

2020 Jan 02

Tamar Bar-On (BIU): Profinite completion of free profinite groups

12:00pm to 1:00pm

Location:

Seminar room 209, Manchester Building, Givat ram

Abstract: The profinite completion of a free profinite group on an infinite set of generators is a profinite group of greater rank. However, it is still unknown whether it is a free profinite group as well. I am going to present some partial results regarding this question.
2020 Jan 02

Groups & Dynamics Seminar. Maria Gerasimova (BIU) : “Isoperimetry, Littlewood functions, and unitarisability of group”

10:00am to 11:00am

Location:

Ross 70 a
Let Γ be a discrete group. A group Γ is called unitarisable if for any Hilbert space H and
any uniformly bounded representation π : Γ → B(H) of Γ on H there exists a bounded operator
S : H → H such that S^{−1}π(g)S is a unitary representation for any g ∈ Γ. It is well known that
amenable groups are unitarisable. It has been open ever since whether amenability characterises unitarisability of groups.
Dixmier: Are all unitarisable groups amenable?
One of the approaches to study unitarisability is related to the space of the Littlewood functions
2020 Jan 08

Special Analysis Seminar: Andrew Ahn (MIT) "Largest Singular Values of Products of \beta-Ensembles"

2:00pm to 3:00pm

Location:

221B

Title:Largest Singular Values of Products of \beta-Ensembles

2020 Mar 31

Or Landesberg

12:00pm to 1:00pm

2019 Dec 26

Avinoam Mann (HUJI): Growth of groups and the word problem

12:00pm to 1:00pm

Location:

Seminar room 209, Manchester building
2019 Dec 25

Special dynamics seminar: Asaf Katz (Chicago) - Measure rigidity of Anosov flows via the factorization method

1:30pm to 3:30pm

Location:

Ross 70
Title - Measure rigidity of Anosov flows via the factorization method.

Abstract: Anosov flows are central objects in dynamics, generalizing the basic example of a geodesic flow over a Riemann surface.

In the talk we will introduce those flows and their dynamical behavior.
Moreover, we show how the factorization method, pioneered by Eskin and Mirzakhani in their groundbreaking work about measure rigidity for the moduli space of translation surfaces, can be adapted to smooth ergodic theory and in particular towards the study of Anosov flows.
2020 Jan 09

Ted Chinburg (U Penn): Using capacity theory to plug leaks

12:00pm to 1:00pm

Location:

Manchester Building, Room 209
January 9, 12:00-13:00, Seminar room 209, Manchester building.
2019 Dec 18

Logic Seminar - Jouko Vaananen

11:00am to 1:00pm

Location:

Ross building - Room 63

Jouko Vaananen will speak about some new infinitary logics.

On some new infinitary logics

Abstract:
2019 Dec 18

Special Analysis and Mathematical Physics Seminar: Eliran Subag (Courant) "Spherical spin glass models"

2:30pm to 3:30pm

Location:

221B

Title: Spherical spin glass models

Abstract: In the 70s, physicists proposed several models fordisordered magnetic alloys called spin glass models. Mathematically, thespherical models are random functions on the sphere in high-dimensions, andmany of the questions physicists are interested in can be phrased aspurely mathematical questions about geometric properties, extreme values,critical points, and Gibbs measures of random functions and the interplaybetween them.

2019 Dec 31

Mike Hochman (HUJI) Equidistribution for toral endomorphisms

2:00pm to 3:00pm

Location:

Ross 70

Abstract: Host proved a strengthening of Rudolph and Johnson's measure rigidity theorem: if a probability measure is invariant, ergodic and has positive entropy for the map x2 mod 1, then a.e. point equidisitrbutes under x3 mod 1. Host also proved a version for toral endomorphisms, but its hypotheses are in some ways too strong, e.g. it requires one of the maps to be expanding, so it does not apply to pairs of  automorphisms. In this talk I will present an extension of Host's result (almost) to its natural generality.