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Department of Mathematics: Faculty Publications

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Document Type

Article

Date of this Version

10-16-2016

Citation

Copyright by THETA, 2017

Comments

J. OPERATOR THEORY 78:2(2017), 357–416 doi: 10.7900/jot.2016sep15.2128

Abstract

We give general structure theory for pairs (C,D) of unital C*- algebras where D is a regular and abelian C*-subalgebra of C.

When D is maximal abelian in C, we prove existence and uniqueness of a completely positive unital map E of C into the injective envelope I(D) of D such that EjD = idD; E is a useful replacement for a conditional expectation when no expectation exists. When E is faithful, (C,D) has numerous desirable properties: e.g. the linear span of the normalizers has a unique minimal C*- norm; D norms C; and isometric isomorphisms of norm-closed subalgebras lying between D and C extend uniquely to their generated C8-algebras.

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