Cuspidal endo-support and strong beta extensions

TL;DR

The paper establishes the existence of maximal semisimple characters in smooth representations of certain p-adic groups, introduces cuspidal endo-support, and develops beta extensions for type construction.

Contribution

It introduces cuspidal endo-support and beta extensions for strong facets, advancing the construction and analysis of types in representation theory of p-adic groups.

Findings

Every smooth representation contains a maximal semisimple character.

Defined support for endo-parameters and related it to cuspidal support.

Beta extensions for strong facets are sufficient for type construction.

Abstract

Let $G$ be an inner form of a general linear group or classical group over a non-archimedean local field of residual characteristic $p$, assumed odd in the classical case. We prove that every smooth representation of $G$ over an algebraically closed field $R$ of characteristic $\ell\neq p$ contains a maximal semisimple character, i.e., one for which the point in the building of the corresponding centralizer is a vertex. Further, for every endo-parameter adapted to $G$, we define its support, which leads also to the notion of cuspidal endo-support of an irreducible representation, and we relate this to its cuspidal support. We also introduce beta extensions for strong facets in the building of a centralizer, and show these are sufficient for the construction of types. These results are used in a subsequent paper to decompose the category of smooth $R$-representations of $G$.