Appears in collection : 2022 - T2 - WS3 - Hyperbolic groups and their generalisations

Given compact length spaces $X_1$ and $X_2$ with a common universal cover, it is natural to ask whether $X_1$ and $X_2$ have a common finite cover. In particular, are there properties of $X_1$ and $X_2$, or of their fundamental groups, that guarantee the existence of a common finite cover? We will discuss several examples, as well as my new result which concerns the case where the common universal cover is a right-angled building. Examples of right-angled buildings include products of trees and Davis complexes of right-angled Coxeter groups. My new result will be stated in terms of weak commensurability of lattices in the automorphism group of the building.