Scattering theory on Locally Symmetric Spaces

Abstract: In 1976, Victor Guillemin published a paper discussing geometric scattering theory, in which he related the Lax-Phillips Scattering matrices (associated to a noncompact hyperbolic surface with cusps) and the sojourn times associated to a set of geodesics which run to infinity in either direction. Later, the work of Guillemin was generalized to locally symmetric spaces by Lizhen Ji and Maciej Zworski. In the case of a $\Q$-rank one locally symmetric space $\Gamma \backslash X$, they constructed a class of scattering geodesics which move to infinity in both directions and are distance minimizing near both infinities. An associated sojourn time was defined for such a scattering geodesic, which is the time it spends in a fixed compact region. One of their main results was that the frequencies of oscillation coming from the singularities of the Fourier transforms of scattering matrices on $\Gamma \backslash X$ occur at sojourn times of scattering geodesics on the locally symmetric space.

In this talk I will review the work of Guillemin, Ji and Zworski as well as discuss the work from my doctoral dissertation on analogous results for higher rank locally symmetric spaces. In particular, I will describe higher dimensional analogues of scattering geodesics called $\textbf{Scattering Flat}$ and study these flats in the case of the locally symmetric space given by the quotient $SL(3,\mathbb{Z}) \backslash SL(3,\mathbb{R}) / SO(3)$. A parametrization space is discussed for such scattering flats as well as an associated vector valued parameter (bearing similarities to sojourn times) called $\textbf{sojourn vector}$ and these are related to the frequency of oscillations of the associated scattering matrices coming from the minimal parabolic subgroups of $\text{SL}(3,\mathbb{R})$. The key technique is the factorization of higher rank scattering matrices.

number theoryrepresentation theory

Audience: researchers in the topic

Geometry, Number Theory and Representation Theory Seminar