Proceedings of the London Mathematical Society Advance Access originally published online on July 5, 2007
Proceedings of the London Mathematical Society 2008 96(1):1-25; doi:10.1112/plms/pdm023
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© 2007 London Mathematical Society
Stability in the Cuntz semigroup of a commutative C*-algebra
Department of Mathematics and Statistics
York University
4700 Keele Street
Toronto
Ontario, M3J 1P3
Canada
Received 12 September 2006. Revision received 1 March 2007.
Let A be a C*-algebra. The Cuntz semigroup W( A) is an analogue for positive elements of the semigroup V( A) of Murray-von Neumann equivalence classes of projections in matrices over A. We prove stability theorems for the Cuntz semigroup of a commutative C*-algebra which are analogues of classical stability theorems for topological vector bundles over compact Hausdorff spaces.
Let SDG denote the class of simple, unital, and infinite-dimensional AH algebras with slow dimension growth, and let A be an element of SDG. We apply our stability theorems to obtain the following:
- A has strict comparison of positive elements;
- W(A) is recovered functorially from the Elliott invariant of A;
- the lower semicontinuous dimension functions on A are weak-* dense in the dimension functions on A;
- the dimension functions on A form a Choquet simplex.
2000 Mathematics Subject Classification 46L35, 46L80.