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Subquotients of Hecke C*-algebras

Published online by Cambridge University Press:  04 August 2005

NATHAN BROWNLOWE
Affiliation:
School of Mathematical and Physical Sciences, University of Newcastle, NSW 2308, Australia (e-mail: [email protected], [email protected])
NADIA S. LARSEN
Affiliation:
Department of Mathematics, Institute for Mathematical Sciences, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark (e-mail: [email protected]) Department of Mathematics, University of Oslo, P.O. Box 1053, Blindern, N-0316 Oslo, Norway
IAN F. PUTNAM
Affiliation:
Department of Mathematics and Statistics, University of Victoria, British Columbia V8W 3P4, Canada (e-mail: [email protected])
IAIN RAEBURN
Affiliation:
School of Mathematical and Physical Sciences, University of Newcastle, NSW 2308, Australia (e-mail: [email protected], [email protected])

Abstract

We realize the Hecke C*-algebra $\mathcal{C}_{\mathbb{Q}}$ of Bost and Connes as a direct limit of Hecke C*-algebras which are semigroup crossed products by $\mathbb{N}^F$, for F a finite set of primes. For each approximating Hecke C*-algebra we describe a composition series of ideals. In all cases there is a large type I ideal and a commutative quotient, and the intermediate subquotients are direct sums of simple C*-algebras. We can describe the simple summands as ordinary crossed products by actions of $\mathbb{Z}^S$ for S a finite set of primes. When $\vert S\vert =1$, these actions are odometers and the crossed products are Bunce–Deddens algebras; when $\vert S\vert >1$, the actions are an apparently new class of higher-rank odometer actions, and the crossed products are an apparently new class of classifiable AT-algebras.

Type
Research Article
Copyright
2005 Cambridge University Press

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