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Homotopy Classification of Projections in the Corona Algebra of a Non-simple C*-algebra

Published online by Cambridge University Press:  20 November 2018

Lawrence G. Brown  and
Hyun Ho Lee
Lawrence G. Brown
Affiliation:
Department of Mathematics, Purdue University, West Lafayette, USA 47907 email: [email protected]
Hyun Ho Lee
Affiliation:
Department of Mathematics, University of Ulsan, Ulsan, Korea 680-749 email: [email protected]
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Abstract

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We study projections in the corona algebra of $C\left( X \right)\,\otimes \,K$, where $K$ is the ${{C}^{*}}$-algebra of compact operators on a separable infinite dimensional Hilbert space and $X\,=\,[0,\,1],\,[0,\,\infty ),\,(-\infty ,\,\infty ),\,\text{or}\,\text{ }\!\![\!\!\text{ 0,}\,\text{1 }\!\!]\!\!\text{ / }\!\!\{\!\!\text{ 0,}\,\text{1 }\!\!\}\!\!\text{ }$. Using BDF's essential codimension, we determine conditions for a projection in the corona algebra to be liftable to a projection in the multiplier algebra. We also determine the conditions for two projections to be equal in ${{K}_{0}}$, Murray-von Neumann equivalent, unitarily equivalent, or homotopic. In light of these characterizations, we construct examples showing that the equivalence notions above are all distinct.

Keywords

46L0546L80essential codimensioncontinuous field of Hilbert spacesCorona algebra
Type
Research Article
Information
Canadian Journal of Mathematics , Volume 64 , Issue 4 , 01 August 2012 , pp. 755 - 777
Copyright
Copyright © Canadian Mathematical Society 2012

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