A reformulation of the conjecture of Prasad and Takloo-Bighash

Abstract

Prasad and Takloo-Bighash proposed a conjecture which predicts a necessary condition in terms of epsilon factors for representations of $\mathrm{GL}_n(F)$ and its inner forms to have linear periods. In this rather expository article, we reformulate their conjecture in the following form: The distinguished members in each generic $L$-packet $Π_ϕ$ are determined by the characters of the component group $S_ϕ$ and local epsilon factors. We follow Aubert et al.\,for the definitions of the $L$-packets and the component groups. We observe that under some hypotheses, the reformulated conjecture follows from the conjectural multiplicity formula recently proposed by Chen Wan for general spherical varieties and the conjectural integral formula for epsilon factors which we propose in this article.