Events & Seminars

2017 Nov 16

Colloquium: John R. Klein (Wayne State U.) - "Algebraic Topology and Fluctuations"

2:40pm to 3:40pm

Location: 

Manchester Building (Hall 2), Hebrew University Jerusalem
This talk will investigate a certain class of continuous time Markov processes using machinery from algebraic topology. To each such process, we will associate a homological observable, the average current, which is a measurement of the net flow of probability of the system. We show that the average current quantizes in the low temperature limit. We also explain how the quantized version admits a topological description.
2017 Nov 04

Colloquium: Michael Brandenbursky (BGU) - "Entropy, metrics and quasi-morphisms"

2:30pm to 3:30pm

Location: 

Manchester Building (Hall 2), Hebrew University Jerusalem
One of the mainstream and modern tools in the study of non abelian groups are quasi-morphisms. These are functions from a group to the reals which satisfy homomorphism condition up to a bounded error. Nowadays they are used in many fields of mathematics. For instance, they are related to bounded cohomology, stable commutator length, metrics on diffeomorphism groups, displacement of sets in symplectic topology, dynamics, knot theory, orderability, and the study of mapping class groups and of concordance group of knots.
2017 Nov 02

Colloquium: Michael Brandenbursky (BGU) "Entropy, metrics and quasi-morphisms."

2:30pm to 3:30pm

Location: 

Manchester Building (Hall 2), Hebrew University Jerusalem
One of the mainstream and modern tools in the study of non abelian groups are quasi-morphisms. These are functions from a group to the reals which satisfy homomorphism condition up to a bounded error. Nowadays they are used in many fields of mathematics. For instance, they are related to bounded cohomology, stable commutator length, metrics on diffeomorphism groups, displacement of sets in symplectic topology, dynamics, knot theory, orderability, and the study of mapping class groups and of concordance group of knots.
2017 Dec 18

SPECIAL Jerusalem Analysis and PDEs seminar: "Steady Water Waves" Walter Strauss (Brown University)

4:00pm to 5:00pm

Location: 

Ross 63
I will consider classical 2D traveling water waves with vorticity. By means of local and global bifurcation theory using topological degree, we can prove that there exist many such waves. They are exact smooth solutions of the Euler equations with the physical boundary conditions. Some of the waves are quite tall and steep and some are overhanging. There are periodic ones and solitary ones. I will exhibit some numerical computations of such waves. New analytical results will be presented on waves with favorable vorticity.
2017 Jun 08

Wolf Prize Lecture - Rick Schoen (Stanford): The geometry of eigenvalue extremal problems

11:00am to 12:00pm

Location: 

Levin building, lecture hall 8
Title: “The geometry of eigenvalue extremal problems” Abstract: When we choose a metric on a manifold we determine the spectrum of the Laplace operator. Thus an eigenvalue may be considered as a functional on the space of metrics. For example the first eigenvalue would be the fundamental vibrational frequency. In some cases the normalized eigenvalues are bounded independent of the metric. In such cases it makes sense to attempt to find critical points in the space of metrics. In this talk we will survey two cases in which progress has been made focusing primarily on the case of surfaces with
2017 Jan 19

Special colloquium: Asaf Katz (HUJI Perlman prize) "Sparse equidistribution in unipotent flows"

4:00pm to 5:00pm

Location: 

Manchester building room 2
Abstract - Equidistribution problems, originating from the classical works of Kronecker, Hardy and Weyl about equidistribution of sequences mod 1, are of major interest in modern number theory. We will discuss how some of those problems relate to unipotent flows and present a conjecture by Margulis, Sarnak and Shah regarding an analogue of those results for the case of the horocyclic flow over a Riemann surface. Moreover, we provide evidence towards this conjecture by bounding from above the Hausdorff dimension of the set of points which do not equidistribute.
2015 Oct 22

Colloquium: Nir Avni (Northwestern), "Counting points and counting representations"

2:30pm to 3:30pm

Title: Counting points and counting representations Abstract: I will talk about the following questions: 1) Given a system of polynomial equations with integer coefficients, how many solutions does it have in the ring Z/N? 2)​ Given a polynomial map f:R^a-->R^b and a smooth, compactly supported measure m on R^a, does the push-forward of m by f have bounded density? 3) Given a lattice in a higher rank Lie group (say, SL(n,Z) for n>2). How many d-dimensional representations does it ​have?

Pages