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Strict Comparison of Positive Elements in Multiplier Algebras

Published online by Cambridge University Press:  20 November 2018

Victor Kaftal ,
Ping Wong Ng  and
Shuang Zhang
Victor Kaftal
Affiliation:
Department of Mathematics, University of Cincinnati, P. O. Box 210025, Cincinnati, OH, 45221-0025, USA e-mail: victor.kaftal@uc.edu
Ping Wong Ng
Affiliation:
Department of Mathematics, University of Louisiana, 217 Maxim D. Doucet Hall, P.O. Box 43568 Lafayette, Louisiana, 70504-3568, USA e-mail: png@louisiana.edu
Shuang Zhang
Affiliation:
Department of Mathematics, University of Cincinnati, P.O. Box 210025, Cincinnati, OH, 45221-0025, USA e-mail: zhangs@ucmail.uc.edu
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Abstract

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Main result: If a ${{C}^{*}}$-algebra $\mathcal{A}$ is simple, $\sigma $-unital, has finitely many extremal traces, and has strict comparison of positive elements by traces, then its multiplier algebra $\mathcal{M}\left( \mathcal{A} \right)$ also has strict comparison of positive elements by traces. The same results holds if finitely many extremal traces is replaced by quasicontinuous scale. A key ingredient in the proof is that every positive element in the multiplier algebra of an arbitrary $\sigma $-unital ${{C}^{*}}$ -algebra can be approximated by a bi-diagonal series. As an application of strict comparison, if $\mathcal{A}$ is a simple separable stable ${{C}^{*}}$ -algebra with real rank zero, stable rank one, and strict comparison of positive elements by traces, then whether a positive element is a positive linear combination of projections is determined by the trace values of its range projection.

Keywords

46L0546L3546L4547C15strict comparisonbi-diagonal formpositive combinations
Type
Research Article
Information
Canadian Journal of Mathematics , Volume 69 , Issue 2 , 01 April 2017 , pp. 373 - 407
Copyright
Copyright © Canadian Mathematical Society 2017

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