A weighted vertical Sato-Tate law for Maaß forms on $\rm{GSp}_4$
Félicien Comtat
TL;DR
<3-5 sentence high-level summary>This paper establishes a weighted vertical Sato-Tate law for Satake parameters of Maaß forms on GSp4 in the level aspect, proving that a natural spectral-weighted average of Satake parameters converges to the GSp4 Sato-Tate measure as the level grows. The authors reduce the problem to the Kuznetsov formula on GSp4, reduce and bound the continuous spectrum via a detailed analysis of double cosets P(A_f)ackslash G(A_f)/H, and compute ramified local integrals for all ramified parabolic subgroups. They also treat the Archimedean contributions through explicit Jacquet- and Whittaker-type integrals and establish lower bounds for L-values needed to control the spectral weights. The results yield a cuspidal refinement in the squarefree level case and illustrate deep interactions between global automorphic spectral data and local representation theory in higher rank.
Abstract
We prove a weighted Sato-Tate law for the Satake parameters of automorphic forms on $\rm{GSp}_4$ with respect to a fairly general congruence subgroup $H$ whose level tends to infinity. When the level is squarefree we refine our result to the cuspidal spectrum. The ingredients are the $\rm{GSp}_4$ Kuznetsov formula and the explicit calculation of local integrals involved in the Whittaker coefficients of $\rm{GSp}_4$ Eisenstein series. We also discuss how the problem of bounding the continuous spectrum in the level aspect naturally leads to some combinatorial questions involving the double cosets in $P \backslash G / H$, for each parabolic subgroup $P$.
