On Arthur's Φ-Function

Abstract

Write $Θ^E$ for the stable character associated to a finite dimensional representation $E$ of a connected real reductive group $G$. Let $M$ be the centralizer of a maximal torus $T$, and denote by $Φ_M(\gm,Θ^E)$ Arthur's extension of $ |D_M^G(\gm)|^{\half} Θ^E(\gm)$ to $T(\R)$. In this paper we give a simple explicit expression for $Φ_M(\gm,Θ^E)$, when $\gm$ is elliptic in $G$.

11 pages