The Ranking-Selberg integral on ${\bf GSp(2)}$ for square free levels
Seiji Kuga, Masao Tsuzuki
TL;DR
The paper develops an explicit global–local framework for the Rankin–Selberg integral on ${\bf GSp}_2$, expressing the adelic integral for vector-valued Siegel cusp forms of square-free level in terms of the spinor $L$-function. It combines Eisenstein series with Bessel models, employs Pitale–Schmidt newvectors, and computes a wide array of local zeta integrals across unramified and ramified cases to obtain exact local–global identities. A spectral average is derived, yielding an explicit formula involving $\widehat{L}(s+1/2,\pi,\mu)$ and local periods, with asymptotic results showing vanishing contributions from old forms and certain lifts in the level-aspect. The work also provides detailed computations of ramified Gross–Prasad-type local periods and sets up a robust framework for relative trace formula applications in this setting, linking global automorphic data to precise local invariants.
Abstract
We explicitly compute the Rankin-Selberg type integral introduced by Piatetski-Shapiro over adeles for vector-valued Siegel cusp forms of square-free levels $Γ_0(N)$. On the way, for particular test functions in the Bessel models of irreducible admissible representations, exact evaluations of the local zeta-integrals are given.
