Mathematical Proceedings of the Cambridge Philosophical Society

Imprimitivity for C*-coactions of non-amenable groups 1

a1 Department of Mathematics, University of Newcastle, Newcastle, New South Wales 2308, Australia; e-mail:
a2 Department of Mathematics, Arizona State University, Tempe, Arizona 85287; e-mail:


We give a condition on a full coaction (A, G, δ) of a (possibly) non-amenable group G and a closed normal subgroup N of G which ensures that Mansfield imprimitivity works; i.e. that A×δ[mid R:]G/N is Morita equivalent to A×δ G×δ^rN. This condition obtains if N is amenable or δ is normal. It is preserved under Morita equivalence, inflation of coactions, the stabilization trick of Echterhoff and Raeburn, and on passing to twisted coactions.

(Received December 12 1995)
(Revised June 5 1996)


1 This research was partially supported by the National Science Foundation under Grant No. DMS9401253, and by the Australian Research Council.