Representing some II$_1$ factors in $L^2(\Lambda \backslash G)$

Abstract

Let $G$ be $PGL(n,F)$, $n \geq 3$, $F$ a certain non-archimedean local field; or let $G$ be $PSL(2,\mathbb{R}) \times \cdots \times PSL(2,\mathbb{R})$. Let $\Gamma$ be a lattice in $G$, and let $( \Lambda_n )$ be a sequence of lattices in $G$ satisfying the pointwise limit multiplicity property. In this note, we explain how the pointwise limit multiplicity property can be combined with a generalization of a theorem in \cite{ghj} to give representations of the II$_1$ factor $R \Gamma$ on a subspace of $L^2(\Lambda_i \backslash G)$ for some $\Lambda_i$ in $( \Lambda_n )$. This extends a result in the author's dissertation \cite{ruthphd}.