A note on a classical relative trace formula
Zhining Wei
TL;DR
This note presents a classical derivation of a relative trace formula for holomorphic cusp forms on $\mathrm{SL}_2(\mathbb{Z})$, yielding a closed formula for the eigenvalue-weighted second moment of central $L$-values. It decomposes the trace into spectral and geometric sides, with explicit expressions for singular and regular orbital integrals and a regularization that handles divergences, ultimately matching Kuznetsov’s preprint (and Iwaniec–Sarnak). The main result expresses the weighted second moment as $M_2(n;s_1,s_2)+E(n;s_1,s_2)$, with a detailed breakdown of terms from the geometric side and their analytic continuations, and a corollary at $(s_1,s_2)=(0,0)$. The approach combines classical kernel methods with hypergeometric representations and divisor arithmetic to produce explicit, computable terms, reinforcing connections to the Kuznetsov framework and related trace-formula techniques.
Abstract
In this note, we derive a relative trace formula (RTF) using classical methods. We obtain a closed formula for the second moment of the central values of holomorphic cusp forms, a result originally established in Kuznetsov's preprint.
