Boundary maps and reducibility for cocycles into CAT(0)-spaces (2005.10529v2)

Abstract: We prove that a non-elementary measurable cocycle in the isometry group of a CAT(0)-space of finite telescopic dimension admits a Furstenberg map. We also show that a maximal cocycle $\sigma:\Gamma \times X \rightarrow \text{PU}(p,\infty)$ where $\Gamma < \text{PU}(n,1)$ is a torsion-free lattice and $(X,\mu_X)$ is a ergodic standard Borel $\Gamma$-space is finitely reducible. As a consequence, we prove an infinite dimensional rigidity phenomenon for cocycles.