Publication Details

An Huef, A., Kaliszewski, S., Raeburn, I. & Williams, D. P. (2011). Naturality of Rieffel's Morita equivalence for proper actions. Algebras and Representation Theory, 14 (3), 515-543.


Suppose that a locally compact group G acts freely and properly on the right of a locally compact space T . Rieffel proved that if is an action of G on a C*-algebra A and there is an equivariant embedding of C0(T ) in M(A), then the action α of G on A is proper, and the crossed product Aα,rG is Morita equivalent to a generalised fixed-point algebra Fix(A,α ) in M(A)α . We show that the assignment (A,α) → Fix(A,α ) extends to a functor Fix on a category of C*-dynamical systems in which the isomorphisms are Morita equivalences, and that Rieffel’s Morita equivalence implements a natural isomorphism between a crossed-product functor and Fix. From this, we deduce naturality of Mansfield imprimitivity for crossed products by coactions, improving results of Echterhoff-Kaliszewski-Quigg-Raeburn and Kaliszewski-Quigg-Raeburn, and naturality of a Morita equivalence for graph algebras due to Kumjian and Pask.



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