A spectral theory of zeta functions of function fields

Abstract

We study Hilbert spaces constructed from the Weil quadratic form associated with the zeta function of a curve over a finite field, together with self-adjoint extensions of the differentiation operator on these spaces. For a distinguished family of these extensions, we prove that the eigenvalues converge to the ordinates of the zeros of the zeta function and that the corresponding entire spectral functions, after normalization, converge locally uniformly to an infinite product determined by these zeros. These limits occur as the interval parameter approaches a finite endpoint, rather than infinity as in the setting of the Riemann zeta function. We also realize the global Hilbert space through the Rosati trace pairing and show that translation by $\log q$ is unitarily equivalent to multiplication by normalized Frobenius. This provides a geometric model for the analogous analytic constructions associated with the Riemann zeta function.