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Search: MSC category 46L55 ( Noncommutative dynamical systems [See also 28Dxx, 37Kxx, 37Lxx, 54H20] )

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1. CJM 2008 (vol 60 pp. 975)

Boca, Florin P.
An AF Algebra Associated with the Farey Tessellation
We associate with the Farey tessellation of the upper half-plane an AF algebra $\AA$ encoding the ``cutting sequences'' that define vertical geodesics. The Effros--Shen AF algebras arise as quotients of $\AA$. Using the path algebra model for AF algebras we construct, for each $\tau \in \big(0,\frac{1}{4}\big]$, projections $(E_n)$ in $\AA$ such that $E_n E_{n\pm 1}E_n \leq \tau E_n$.

Categories:46L05, 11A55, 11B57, 46L55, 37E05, 82B20

2. CJM 2006 (vol 58 pp. 39)

Exel, R.; Vershik, A.
$C^*$-Algebras of Irreversible Dynamical Systems
We show that certain $C^*$-algebras which have been studied by, among others, Arzumanian, Vershik, Deaconu, and Renault, in connection with a measure-preserving transformation of a measure space or a covering map of a compact space, are special cases of the endomorphism crossed-product construction recently introduced by the first named author. As a consequence these algebras are given presentations in terms of generators and relations. These results come as a consequence of a general theorem on faithfulness of representations which are covariant with respect to certain circle actions. For the case of topologically free covering maps we prove a stronger result on faithfulness of representations which needs no covariance. We also give a necessary and sufficient condition for simplicity.

Categories:46L55, 37A55

3. CJM 2005 (vol 57 pp. 983)

an Huef, Astrid; Raeburn, Iain; Williams, Dana P.
A Symmetric Imprimitivity Theorem for Commuting Proper Actions
We prove a symmetric imprimitivity theorem for commuting proper actions of locally compact groups $H$ and $K$ on a $C^*$-algebra.

Categories:46L05, 46L08, 46L55

4. CJM 2003 (vol 55 pp. 1302)

Katsura, Takeshi
The Ideal Structures of Crossed Products of Cuntz Algebras by Quasi-Free Actions of Abelian Groups
We completely determine the ideal structures of the crossed products of Cuntz algebras by quasi-free actions of abelian groups and give another proof of A.~Kishimoto's result on the simplicity of such crossed products. We also give a necessary and sufficient condition that our algebras become primitive, and compute the Connes spectra and $K$-groups of our algebras.

Categories:46L05, 46L55, 46L45

5. CJM 1999 (vol 51 pp. 745)

Echterhoff, Siegfried; Quigg, John
Induced Coactions of Discrete Groups on $C^*$-Algebras
Using the close relationship between coactions of discrete groups and Fell bundles, we introduce a procedure for inducing a $C^*$-coaction $\delta\colon D\to D\otimes C^*(G/N)$ of a quotient group $G/N$ of a discrete group $G$ to a $C^*$-coaction $\Ind\delta\colon\Ind D\to \Ind D\otimes C^*(G)$ of $G$. We show that induced coactions behave in many respects similarly to induced actions. In particular, as an analogue of the well known imprimitivity theorem for induced actions we prove that the crossed products $\Ind D\times_{\Ind\delta}G$ and $D\times_{\delta}G/N$ are always Morita equivalent. We also obtain nonabelian analogues of a theorem of Olesen and Pedersen which show that there is a duality between induced coactions and twisted actions in the sense of Green. We further investigate amenability of Fell bundles corresponding to induced coactions.


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