Math Colloquium

Math colloquium meets on Mondays at 12:15 in Schreiber 006, Tel Aviv University.

Fall 2006

30.10.2006, 12:15
Yehuda Shalom , Tel Aviv University, Israel
The algebraization of Kazhdan's property (T)

13.11.2006, 12:15
Misha Kapovich , UC Davis, USA
Leonard Blumenthal Lectures in Geometry.

Products of matrices.

ABSTRACT: I will discuss some very basic problems of linear algebra, i.e. how eigenvalues and singular values of matrices behave under the addition and multiplication. I will explain the relation between these problems and geometry of triangles.

20.11.2006, 12:15
Gady Kozma ,Weizmann Institute, Israel
One-dimensional long-range diffusion-limited aggregation.

ABSTRACT: We investigate this model for random self-organizing fractals and calculate the dimension as a function of the parameters. We shall expose no less than 3 phase transitions, and try to explain their origin. Joint work with Gideon Amir, Omer Angel and Itai Benjamini.

27.11.2006, 12:15
Paul Biran ,Tel Aviv University, Israel
Symplectic Morse Theory.

11.12.2006, 12:15
George Zaslavsky , Courant Institute, New York, USA
Fractional dynamics for long space-time interactions.

18.12.2006, 12:15
Boris Mityagin , Ohio State University, USA
Instability zones for periodic 1D Schroedinger and Dirac operators.

ABSTRACT: Spectra of the Schroedinger and Dirac operators with periodic potentials on the real line R have band structure, i.e., the segments of continuous spectrum alternate with spectral gaps, or instability zones. The sizes of these zones decay, and the rate of that decay depends on the smoothness of the potential. One can go to the opposite direction and make conclusion about the smoothness of a potential by the rate of decay of its instability zones. On the level of infinitely differentiable or analytic functions this phenomenon has been understood in the case of Schroedinger operators in the 1960~Rs and 70~Rs. However, only recently the relationship between the potential smoothness and the rate of decay of instability zones became completely understood and analyzed for broad range of classes of differentiable functions; for Dirac operators, not only for Hill~Schroedinger operators; both in the self~adjoint and non~self~adjoint cases. The talk gives a survey of these results based on the methods developed by Plamen Djakov and the speaker. Their paper appeared in Uspehi 61:4 (2006), 77-182. (See English transl. in Russian Mathematical Surveys.)

01.01.2007, 12:15
Alex Furman , University of Illinois at Chicago, USA
Superrigidity revisited.

ABSTACT: In the talk I will discuss the celebrated superrigidity theorem(s) of Margulis from the 70s and some of the many more recent results inspired, motivated and analogous to the original superrigidity theorems. I will describe a unified approach to some of these superrigidity phenomena (based on joint works with Uri Bader).

08.01.2007, 12:15
Joseph Bernstein , Tel Aviv University, Israel
Covexity and subconvexity estimates for triple periods of automorphic functions.

(joint work with Andre Reznikov from Bar Ilan University)
Organizer: Semyon Alesker , e-mail: semyon AT post DOT