A proof of Harish-Chandra's integrability theorem for cuspidal representations of $\mathrm{GL}_n(\mathbb F_\ell((t)))$

Abstract

Consider the Chevalley map $$ p:\mathfrak{gl} _n(F)\to (\mathfrak{gl}_n//\mathrm{GL}_n)(F), $$ where $F=\mathbb{F}_\ell((t))$. We show that the push forward via $p$ of every smooth compactly supported measure on $\mathfrak{gl}_n(F)$ is a measure whose density belongs to $L^q$ for every finite $q$. As a consequence, using the main result of [AGKSc], we obtain local integrability for Harish--Chandra's characters of irreducible cuspidal representations of $\mathrm{GL}_n(F)$.