# Motohashi's fourth moment identity for non-archimedean test functions and applications

## TL;DR

This paper generalizes Motohashi's identity to Dirichlet L-functions with non-archimedean test functions, establishing a new reciprocity formula and deriving sharp bounds for moments and subconvexity in the level aspect.

## Contribution

It introduces a novel generalization of Motohashi's formula to non-archimedean settings and applies it to obtain improved bounds for moments of L-functions.

## Key findings

- Established a new reciprocity formula for Dirichlet L-functions.
- Derived sharp upper bounds for the fourth moment twisted by Dirichlet polynomial squares.
- Improved subconvexity bounds for automorphic L-functions in the level aspect.

## Abstract

Motohashi established an explicit identity between the fourth moment of the Riemann zeta function weighted by some test function and a spectral cubic moment of automorphic L-functions. By an entirely different method, we prove a generalization of this formula to a fourth moment of Dirichlet L-functions modulo q weighted by a non-archimedean test function. This establishes a new reciprocity formula. As an application, we obtain sharp upper bounds for the fourth moment twisted by the square of a Dirichlet polynomial of length q^{1/4}. An auxiliary result of independent interest is a sharp upper bound for a certain sixth moment for automorphic L-functions, which we also use to improve the best known subconvexity bounds for automorphic L-functions in the level aspect.