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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

Using a new definition of a prime ideal of a skew brace A, on set Spec A of prime ideals of A we endow a spectral topology (in the sense of Grothendieck). We characterize irreducible closed subsets of Spec A and prove every irreducible…

Rings and Algebras · Mathematics 2025-04-29 Themba Dube , Amartya Goswami

We explicitly construct Fredholm modules and spectral triples representing any element of $K$-homology groups of Hensel-Steinitz algebras.

Operator Algebras · Mathematics 2025-10-09 Shelley Hebert , Slawomir Klimek , Matt McBride

For a unital C*-algebra A, which is equipped with a spectral triple and an extension T of A by the compacts, we construct a family of spectral triples associated to T and depending on the two positive parameters (s,t). Using Rieffel's…

Operator Algebras · Mathematics 2009-11-13 Erik Christensen , Cristina Ivan

Gelfand - Na\u{i}mark theorem supplies a one to one correspondence between commutative $C^*$-algebras and locally compact Hausdorff spaces. So any noncommutative $C^*$-algebra can be regarded as a generalization of a topological space.…

Operator Algebras · Mathematics 2015-08-25 Petr Ivankov

Given a free action of a compact Lie group $G$ on a unital C*-algebra $\mathcal{A}$ and a spectral triple on the corresponding fixed point algebra $\mathcal{A}^G$, we present a systematic and in-depth construction of a spectral triple on…

Operator Algebras · Mathematics 2022-01-24 Kay Schwieger , Stefan Wagner

This paper extends the notion of a spectral triple to a relative spectral triple, an unbounded analogue of a relative Fredholm module for an ideal $J\triangleleft A$. Examples include manifolds with boundary, manifolds with conical…

K-Theory and Homology · Mathematics 2019-11-28 Iain Forsyth , Magnus Goffeng , Bram Mesland , Adam Rennie

A proper etale Lie groupoid is modelled as a (noncommutative) spectral geometric space. The spectral triple is built on the algebra of smooth functions on the groupoid base which are invariant under the groupoid action. Stiefel-Whitney…

Mathematical Physics · Physics 2014-12-16 Antti J. Harju

For each K-homolgy element of the Sierpinski gasket we construct a spectral triple which will generate that element. We show that there must be certain limits on the choice of the K-homology element if the geometric properties of the gasket…

Operator Algebras · Mathematics 2011-09-22 Erik Christensen , Cristina Ivan , Elmar Schrohe

It is proved that for any cohomology theory A in the sense of [PS] and any essentially k-smooth semi-local X the Cousin complex is exact. As a consequence we prove that for any integer n the Nisnevich sheaf A^n_Nis, associated with the…

Algebraic Geometry · Mathematics 2017-07-07 Ivan Panin

We explain how a simple twisting of the notion of spectral triple allows to incorporate type III examples, such as those arising from the transverse geometry of codimension one foliations. Since the twisting of the commutators turns the…

Operator Algebras · Mathematics 2007-05-23 Alain Connes , Henri Moscovici

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 refine the reconstruction theorem for almost-commutative spectral triples to a result for real almost-commutative spectral triples, clarifying, in the process, both concrete and abstract definitions of real commutative and…

Mathematical Physics · Physics 2014-08-20 Branimir Ćaćić

The machinery of noncommutative geometry is applied to a space of connections. A noncommutative function algebra of loops closely related to holonomy loops is investigated. The space of connections is identified as a projective limit of…

High Energy Physics - Theory · Physics 2009-11-11 Johannes Aastrup , Jesper M. Grimstrup

A regular spectral triple is proposed for a two-dimensional $\kappa$-deformation. It is based on the naturally associated affine group $G$, a smooth subalgebra of $C^*(G)$, and an operator $\caD$ defined by two derivations on this…

Mathematical Physics · Physics 2012-08-07 B. Iochum , T. Masson , A. Sitarz

We explore factorizations of noncommutative Riemannian spin geometries over commutative base manifolds in unbounded KK-theory. After setting up the general formalism of unbounded KK-theory and improving upon the construction of internal…

K-Theory and Homology · Mathematics 2016-10-24 Simon Brain , Bram Mesland , Walter D. van Suijlekom

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

In the context of metric geometry, we introduce a new necessary and sufficient condition for the convergence of an inductive sequence of quantum compact metric spaces for the Gromov-Hausdorff propinquity, which is a noncommutative analogue…

Operator Algebras · Mathematics 2024-03-25 Carla Farsi , Frederic Latremoliere , Judith Packer

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

Examples of noncommutative self-coverings are described, and spectral triples on the base space are extended to spectral triples on the inductive family of coverings, in such a way that the covering projections are locally isometric. Such…

Operator Algebras · Mathematics 2016-12-21 Valeriano Aiello , Daniele Guido , Tommaso Isola
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