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Remarks on complemented subspaces of von Neumann algebras*

Published online by Cambridge University Press:  14 November 2011

G. Pisier
Affiliation:
Mathematics Department, Texas A. and M. University, College Station, TX 77843, U.S.A.; and Equipe d'Analyse, Université Paris 6, Tour 46, 4ème étage, 75230 Paris Cedex 05, France

Synopsis

In this note we include two remarks about bounded (not necessarily contractive) linear projections on a von Neumann algebra. We show that if M is a von Neumann subalgebra of B(H) which is complemented in B(H) and isomorphic to M⊗M, then M is injective (or equivalently M is contractively complemented). We do not know how to get rid of the second assumption on M. In the second part, we show that any complemented reflexive subspace of a C*-algebra is necessarily linearly isomorphic to a Hilbert space.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1992

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