Distinguished Representations for $\rm{SL}_n(D)$ where $D$ is a quaternion division algebra over a $p$-adic field (2501.04500v1)

Abstract: Let $D$ be a quaternion division algebra over a non-archimedean local field $F$ of characteristic zero. Let $E/F$ be a quadratic extension and $\rm{SL}{n}^{*}(E) = {\rm{GL}}{n}(E) \cap \rm{SL}{n}(D)$. We study distinguished representations of $\rm{SL}{n}(D)$ by the subgroup $\rm{SL}{n}^{*}(E)$. Let $\pi$ be an irreducible admissible representation of $\rm{SL}{n}(D)$ which is distinguished by $\rm{SL}{n}^{*}(E)$. We give a multiplicity formula, i.e. a formula for the dimension of the $\mathbb{C}$-vector space ${\rm{Hom}}{\rm{SL}{n}^{*}(E)} (\pi, \mathbbm{1})$, where $\mathbbm{1}$ denotes the trivial representation of $\rm{SL}{n}^{*}(E)$. This work is a non-split inner form analog of a work by Anandavardhanan-Prasad which gives a multiplicity formula for $\rm{SL}{n}(F)$-distinguished irreducible admissible representation of $\rm{SL}{n}(E)$.