On classical doubling method gamma factors for certain depth zero representations

TL;DR

This paper extends the doubling method gamma factors to classical finite groups of Lie type, providing explicit formulas and relating them to depth zero supercuspidal representations.

Contribution

It defines and studies an analogous gamma factor for finite groups, proving multiplicativity and connecting it to existing local constructions.

Findings

Gamma factor is multiplicative.

Explicit formulas in terms of Deligne--Lusztig data.

Connection established with depth zero supercuspidal representations.

Abstract

Piatetski-Shapiro--Rallis discovered an integral representation construction, known as the doubling method, for the tensor product $L$-function of a cuspidal automorphic representation of $G \times \mathrm{GL}_1$, where $G$ is a classical group. Lapid--Rallis defined and studied the counterpart local factors. In this article, following Lapid--Rallis, we define and study an analogous doubling method gamma factor associated to irreducible representations of classical finite groups of Lie type. We prove that this gamma factor is multiplicative and use results of Yost-Wolff--Zelingher to give explicit formulas for it in terms of the Deligne--Lusztig data of the representation in the non-conjugate-dual character case. Finally, we relate our construction to the local construction of Lapid--Rallis via certain depth zero supercuspidal representations of classical groups.