Regular supercuspidal representations

TL;DR

This paper characterizes most supercuspidal representations of tamely ramified reductive p-adic groups via pairs involving elliptic maximal tori and characters, providing explicit constructions and connections to the local Langlands correspondence.

Contribution

It introduces a new root-theoretic characterization of supercuspidal representations and constructs the local Langlands correspondence for these cases in large residual characteristic.

Findings

Most supercuspidal representations arise from pairs (S,θ) with specific properties.

A new expression for roots of unity in the character formula is provided.

The local Langlands correspondence is explicitly constructed and shown to be stable.

Abstract

We show that, in good residual characteristic, most supercuspidal representations of a tamely ramified reductive p-adic group G arise from pairs (S,\theta), where S is a tame elliptic maximal torus of G, and \theta is a character of S satisfying a simple root-theoretic property. We then give a new expression for the roots of unity that appear in the Adler-DeBacker-Spice character formula for these supercuspidal representations and use it to show that this formula bears a striking resemblance to the character formula for discrete series representations of real reductive groups. Led by this, we explicitly construct the local Langlands correspondence for these supercuspidal representations and prove stability and endoscopic transfer in the case of toral representations. In large residual characteristic this gives a construction of the local Langlands correspondence for almost all supercuspidal representations of reductive p-adic groups.