One-cohomology and the uniqueness of the group measure space decomposition of a II1 factor

By S. Vaes. 2010

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We provide a unified and self-contained treatment of several of the recent uniqueness theorems for the group measure space decomposition of a II1 factor. We single out a large class of groups Γ, characterized by a one-cohomology property, and prove that for every free ergodic probability measure preserving action of Γ the associated II1 factor has a unique group measure space Cartan subalgebra up to unitary conjugacy. Our methods follow closely a recent article of Chifan–Peterson, but we replace the usage of Peterson’s unbounded derivations by Thomas Sinclair’s dilation into a malleable deformation by a one-parameter group of automorphisms.

Subfields: Algebra and Number Theory, Mathematical Physics

View Paper: https://www.semanticscholar.org/paper/20ab4ed3d827e2e931a8baab70d45330dc8ce4b7