An asymptotic formula of spectral average of central $L$-values on ${\bf GSp}(2)$ for square free levels
Seiji Kuga, Masao Tsuzuki
TL;DR
The paper develops a novel relative trace formula for ${f PGSp}_2$ that uses Bessel periods and Rankin–Selberg integrals to study the spectral behavior of central spinor L-values for Siegel cusp forms with square-free level. By translating automorphic data through an exceptional isomorphism to an orthogonal setting, the authors derive an explicit main-term formula with a sharp error term and establish a weighted density theorem for Satake parameters, enabling equidistribution results in the weight and level aspects. A key application proves simultaneous non-vanishing of multiple twisted L-values and yields the existence of infinite families of regular algebraic self-dual ${f GL}_4$ representations with large Hecke fields. The approach blends intricate local orbital integrals, stable integrals, and carefully controlled archimedean and p-adic analysis, culminating in a concrete S-factor evaluation and a robust error analysis. This work advances the automorphic density paradigm for ${f PGSp}_2$ and provides new avenues for non-vanishing results and explicit GL4 constructions with arithmetic significance.
Abstract
We develop a new kind of relative trace formulas on ${\bf PGSp}_2$ involving the Bessel periods and the Rankin-Selberg type integral a la Piatetski-Shapiro for Siegel cusp forms on its spectral side. As an application, a version of weighted equidistribution theorems for the Satake parameters of Siegel cusp forms of square-free level and of scalar weights is proved.
