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By employing the external Kasparov product, Hawkins, Skalski, White and Zacharias constructed spectral triples on crossed product C$^\ast$-algebras by equicontinuous actions of discrete groups. They further raised the question for whether…

Operator Algebras · Mathematics 2026-01-28 Mario Klisse

Starting with a spectral triple on a unital $C^{*}$-algebra $A$ with an action of a discrete group $G$, if the action is uniformly bounded (in a Lipschitz sense) a spectral triple on the reduced crossed product $C^{*}$-algebra $A\rtimes_{r}…

Operator Algebras · Mathematics 2022-08-30 P. Antonini , D. Guido , T. Isola , A. Rubin

We give a construction allowing to lift spectral triples to crossed products by Hilbert bimodules. The spectral triple one obtains is a concrete unbounded representative of the Kasparov product of the spectral triple and the…

Operator Algebras · Mathematics 2013-10-23 Olivier Gabriel , Martin Grensing

Given a spectral triple on a unital $C^{*}$-algebra $A$ and an equicontinuous action of a discrete group $G$ on $A$, a spectral triple on the reduced crossed product $C^{*}$-algebra $A\rtimes_r G$ was constructed by Hawkins, Skalski, White…

Operator Algebras · Mathematics 2022-07-26 Alessandro Rubin , Ludwik Dabrowski

We examine the structure of two possible candidates of isometry groups for the spectral triples on $AF$-algebras introduced by Christensen and Ivan. In particular, we completely determine the isometry group introduced by Park, and observe…

Operator Algebras · Mathematics 2023-02-14 J. Bassi , R. Conti

Connes showed that spectral triples encode (noncommutative) metric information. Further, Connes and Moscovici in their metric bundle construction showed that, as with the Takesaki duality theorem, forming a crossed product spectral triple…

Operator Algebras · Mathematics 2012-04-20 Alan L. T. Paterson

We define spectral freeness for actions of discrete groups on C*-algebras. We relate spectral freeness to other freeness conditions; an example result is that for an action of a finite group, spectral freeness is equivalent to strong…

Operator Algebras · Mathematics 2013-08-23 Cornel Pasnicu , N. Christopher Phillips

Given a spectral triple $(A,H,D)$ and a $C^*$-dynamical system $(\mathbf{A}, G, \alpha)$ where $A$ is dense in $\mathbf{A}$ and $G$ is a locally compact group, we extend the triple to a triplet $(\mathcal{B},\mathcal{H},\mathcal{D})$ on the…

Operator Algebras · Mathematics 2015-11-26 Bruno Iochum , Thierry Masson

We propose a construction for spectral triple on algebras associated with subshifts. One-dimensional subshifts provide concrete examples Z-actions on Cantor sets. The C*-algebra of this dynamical system is generated by functions in C(X) and…

Operator Algebras · Mathematics 2015-11-18 Antoine Julien , Ian F. Putnam

We construct the product of real spectral triples of arbitrary finite dimension (and arbitrary parity) taking into account the fact that in the even case there are two possible real structures, in the odd case there are two inequivalent…

Mathematical Physics · Physics 2012-03-20 Ludwik Dabrowski , Giacomo Dossena

Given a spectral triple on a $C^*$-algebra $\mathcal A$ together with a unital injective endomorphism $\alpha$, the problem of defining a suitable crossed product $C^*$-algebra endowed with a spectral triple is addressed. The proposed…

Operator Algebras · Mathematics 2022-04-25 Valeriano Aiello , Daniele Guido , Tommaso Isola

An exotic crossed product is a way of associating a C*-algebra to each C*-dynamical system that generalizes the well-known universal and reduced crossed products. Exotic crossed products provide natural generalizations of, and tools to…

Operator Algebras · Mathematics 2015-10-12 Alcides Buss , Siegfried Echterhoff , Rufus Willett

We review the recent construction of semifinite spectral triples for graph C^*-algebras. These examples have inspired many other developments and we review some of these such as the relation between the semifinite index and the Kasparov…

Operator Algebras · Mathematics 2007-07-27 Alan Carey , John Phillips , Adam Rennie

This survey deals with the construction of a category of spectral triples that is compatible with the Kasparov product in $KK$-theory. These notes serve as an intuitive guide to these results, avoiding the necessary technical proofs. We…

K-Theory and Homology · Mathematics 2013-04-16 Bram Mesland

By considering the general properties of approximate units in differentiable algebras, we are able to present a unified approach to characterising completeness of spectral metric spaces, existence of connections on modules, and the lifting…

Operator Algebras · Mathematics 2016-10-24 Bram Mesland , Adam Rennie

We produce a variety of odd bounded Fredholm modules and odd spectral triples on Cuntz-Krieger algebras by means of realizing these algebras as "the algebra of functions on a non-commutative space" coming from a sub shift of finite type. We…

K-Theory and Homology · Mathematics 2015-03-02 Magnus Goffeng , Bram Mesland

We introduce to spectral noncommutative geometry the notion of tangled spectral triple, which encompasses the anisotropies arising in parabolic geometry as well as the parabolic commutator bounds arising in so-called "bad Kasparov…

Operator Algebras · Mathematics 2026-02-25 Magnus Fries , Magnus Goffeng , Ada Masters

We show how to equip the crossed product between a group of polynomial growth and a compact quantum metric space with a compact quantum metric space structure. When the quantum metric on the base space arises from a spectral triple, which…

Operator Algebras · Mathematics 2024-12-02 Are Austad , Jens Kaad , David Kyed

This is a survey on Kasparov's bivariant $KK$-theory in connection with the Baum-Connes conjecture on the $K$-theory of crossed products $A\rtimes_rG$ by actions of a locally compact group $G$ on a C*-algebra $A$. In particular we shall…

K-Theory and Homology · Mathematics 2017-06-14 Siegfried Echterhoff

We provide sufficient conditions to factorise an equivariant spectral triple as a Kasparov product of unbounded classes constructed from the group action on the algebra and from the fixed point spectral triple. Our results are for the…

K-Theory and Homology · Mathematics 2015-05-13 Iain Forsyth , Adam Rennie
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