2006/05/10 by Alex Furman, Furman, Alex
Mathematics · #22E40 #22F30 #37A17 #37A35 #Advanced Operator Algebra Research #Dynamical Systems (math.DS) #FOS: Mathematics #Geometric and Algebraic Topology #Mathematical Dynamics and Fractals #math.DS #msc:22E40 #msc:22F30 #msc:37A17 #msc:37A35
paper · pdf · doi:10.48550/arxiv.math/0605273
arxiv created 2006/05/10 · openalex publication_date 2006/05/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider the problems of measurable isomorphisms and joinings, measurable centralizers and quotients for certain classes of ergodic group actions on infinite measure spaces. Our main focus is on systems of algebraic origin: actions of lattices and other discrete subgroups on homogeneous spaces G/H where H is a sufficiently rich unimodular subgroup in a semi-simple group G. We also consider actions of discrete subgroups of isometries Isom(X) of a pinched negative curvature space X, acting on the space of horospheres Hor(X). For such systems we prove that the only measurable isomorphisms, joinings, quotients etc. are the obvious algebraic (or geometric) ones. This work was inspired by the previous work of Shalom and Steger, but uses completely different techniques which lead to more general results.