The next APDE seminar will take place Wednesday, Nov 28, in 740 Evans from 3-4pm.

Title: Illusions: curves of zeros of Selberg zeta functions

Abstract: It is well known (since 1956) that the Selberg Zeta function
for compact surfaces satisfies the “Riemann Hypothesis”: any zero in the
critical strip 0<R(s)<1 is either real or Im(s)=1/2. The question of
location and distribution of the zeros of the Selberg Zeta function
associated to a noncompact hyperbolic surface attracted attention of the
mathematical community in 2014 when numerical experiments by
D. Borthwick showed that for certain surfaces zeros seem to lie on
smooth curves. Moreover, the individual zeros are so close to each other
that they give a visual impression that the entire curve is a zero set.

We will give an overview of the computational methods used, present
recent results, justifying these observations as well as state open
conjectures.

The next APDE seminar will take place Monday, Nov 19, in 740 Evans from 4-5pm.

Title: Rough control for Schr\”odinger operators on 2-tori.

Abstract: I will explain how the results of Bourgain, Burq and the
speaker ’13 can be used to obtain control and observability by rough
functions and sets on 2-tori. We show that for the time dependent
Schrödinger equation, any set of positive measure can be used for
observability and controllability.

For non-empty open sets this follows from the results of Haraux ’89
and Jaffard ’90, while for sufficiently long times and rational tori
this can be deduced from the results of Jakobson ’97.

The next APDE seminar will take place Monday, Nov 5, in 740 Evans from 4-5pm.

title: The Marked Length Spectrum of Anosov manifolds

Abstract: We discuss new results on the geometric problem of determining a Riemannian metric with negative curvature on a closed manifold from the lengths of its periodic geodesics. We obtain local rigidity results in all dimensions using combination of dynamical system results with microlocal analysis. Joint work with Thibault Lefeuvre.