Outer space for RAAGs
The classical symmetric space $Q_n$ of positive definite quadratic forms and Culler Vogtmann Outer Space CV$_n$ are major tools in the study of GL($n, Z$) and Out($F_n$), respectively. The class of right-angled Artin groups (RAAGs) is a natural extension of free groups and free abelian groups, which has featured prominently in the study of CAT(0) cube complexes and low-dimensional topology. Let $A$ be a RAAG. We build a finite-dimensional, contractible outer space $O_A$ on which Out($A$) acts with finite point stabilizers. This construction generalizes that of $Q_n$ and CV$_n$ and blends features of both. In this talk, we will describe the construction of $O_A$, then discuss open questions and directions for further study. This is joint work with Ruth Charney and Karen Vogtmann.