Restricting admissible representations to fixed-point subgroups

TL;DR

This paper explores the relationship between admissible representations of a p-adic group and its fixed-point subgroup under a finite automorphism group, generalizing known results and identifying inertial classes in restricted representations.

Contribution

It establishes a new connection between types for p-adic groups and their fixed-point subgroups, extending previous work by Yu, Kim--Yu, and Fintzen.

Findings

Generalizes the relationship between representations of G and G^Γ

Explicitly identifies inertial classes in restricted representations

Extends Stevens' observations from GL to classical groups

Abstract

Given a $p$-adic group $G$ equipped with an action of a finite group $\Gamma\subset\mathrm{Aut}_F(\mathbf{G})$, and a reductive fixed-point subgroup $G^\Gamma$, we establish a relationship between constructions of types for these two groups due to Yu, Kim--Yu and Fintzen, and generalizes the relationship between general linear and classical groups observed by Stevens. As an application, given a parabolically induced or supercuspidal representation $\pi$ of $G$, we explicitly identify a number of the inertial equivalence classes occurring in the representation $\pi|_{G^{[\Gamma]}}$.