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# Journal of Operator Theory

Volume 64, Issue 2, Fall 2010  pp. 417-434.

Extension of automorphisms to $C^*$ crossed products with non-trivial centre

Authors Roberto Conti (1) and Ezio Vasselli (2)
Author institution: (1) School of Mathematical and Physical Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
(2) Dipartimento di Matematica, Universita di Roma ''La Sapienza'', Piazzale Aldo Moro 5, I-00185 Roma, Italy

Summary:  Given a quasi-special endomorphism $\rho$ of a $C^*$-algebra $\mA$ with nontrivial center, we study an extension problem for automorphisms of $\mA$ to a minimal cross-product $\mB$ of $\mA$ by $\rho$. Exploiting some aspects of the underlying generalized Doplicher--Roberts duality theory based on Pimsner algebras, an obstruction to the existence of such extensions is found and described in terms of sections of a suitable group bundle.

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