Popa’s averaging property for automorphisms on C*-algebras

Mikael Rordam

14:50-15:50，July 30th，2024    Tian Jiabing Building 323

Abstract:

In his study of the relative Dixmier property for von Neumann algebras and C*-algebras, Popa introduced a property of an automorphism, which can be thought of as a twisted Dixmier averaging property. We give an almost complete characterization of when an automorphism has this property. We further show how one can use this property to give much easier and more transparent proofs of a number of results on the inclusion of a C*-algebra into its crossed product C*-algebra by a group of automorphisms, assuming the automorphisms have averaging property.

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