Global Automorphic Sobolev Theory and The Automorphic Heat Kernel

TL;DR

This paper introduces a new method using global automorphic Sobolev theory to construct and analyze the automorphic heat kernel, overcoming previous analytic difficulties and applicable to higher rank symmetric spaces.

Contribution

It develops a general framework for automorphic heat kernels without restrictions on space rank or quotient compactness, using spectral expansion and operator semigroup theory.

Findings

Constructed automorphic heat kernel via spectral expansion

Proved uniqueness of the automorphic heat kernel

Established smoothness through convergence in the $C^ abla$-topology

Abstract

Heat kernels arise in a variety of contexts including probability, geometry, and functional analysis; the automorphic heat kernel is particularly important in number theory and string theory. The typical construction of an automorphic heat kernel as a Poincar\'{e} series presents analytic difficulties, which can be dealt with in special cases (e.g. hyperbolic spaces) but are often sidestepped in higher rank by restricting to the compact quotient case. In this paper, we present a new approach, using global automorphic Sobolev theory, a robust framework for solving automorphic PDEs that does not require any simplifying assumptions about the rank of the symmetric space or the compactness of the arithmetic quotient. We construct an automorphic heat kernel via its automorphic spectral expansion in terms of cusp forms, Eisenstein series, and residues of Eisenstein series. We then prove uniqueness of the automorphic heat kernel as an application of operator semigroup theory. Finally, we prove the smoothness of the automorphic heat kernel by proving that its automorphic spectral expansion converges in the $C^\infty$-topology.