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The structure of crossed products of irrational rotation algebras by finite subgroups of SL2(ℤ)

  • Siegfried Echterhoff , Wolfgang Lück , N. Christopher Phillips and Samuel Walters
Published/Copyright: January 20, 2010
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Journal für die reine und angewandte Mathematik
From the journal Volume 2010 Issue 639

Abstract

Let F ⊆ SL2(ℤ) be a finite subgroup (necessarily isomorphic to one of ℤ2, ℤ3, ℤ4, or ℤ6), and let F act on the irrational rotational algebra Aθ via the restriction of the canonical action of SL2(ℤ). Then the crossed product AθαF and the fixed point algebra are AF algebras. The same is true for the crossed product and fixed point algebra of the flip action of ℤ2 on any simple d-dimensional noncommutative torus AΘ. Along the way, we prove a number of general results which should have useful applications in other situations.

Received: 2008-10-15
Published Online: 2010-01-20
Published in Print: 2010-February

© Walter de Gruyter Berlin · New York 2010

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