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We study spectral action for Riemannian manifolds with boundary, and then generalize this to noncommutative spaces which are products of a Riemannian manifold times a finite space. We determine the boundary conditions consistent with the…

High Energy Physics - Theory · Physics 2010-11-23 Ali H. Chamseddine , Alain Connes

We present a spectral triple for $\kappa$-Minkowski space in two dimensions. Starting from an algebra naturally associated to this space, a Hilbert space is built using a weight which is invariant under the $\kappa$-Poincar\'e algebra. The…

Mathematical Physics · Physics 2013-11-14 Marco Matassa

It is known that the spin structure on a Riemannian manifold can be extended to noncommutative geometry using the notion of a spectral triple. For finite geometries, the corresponding finite spectral triples are completely described in…

High Energy Physics - Theory · Physics 2009-10-30 Thomas Krajewski

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

We construct discrete versions of $\kappa$-Minkowski space related to a certain compactness of the time coordinate. We show that these models fit into the framework of noncommutative geometry in the sense of spectral triples. The dynamical…

High Energy Physics - Theory · Physics 2011-11-28 Bruno Iochum , Thierry Masson , Thomas Schücker , Andrzej Sitarz

Spectral triples (of compact type) are constructed on arbitrary separable quasidiagonal C*-algebras. On the other hand an example of a spectral triple on a non-quasidiagonal algebra is presented.

Operator Algebras · Mathematics 2008-11-04 Adam Skalski , Joachim Zacharias

It is well known that for any irrational rotation number $\a$, the noncommutative torus $\ba_\a$ must have representations $\pi$ such that the generated von Neumann algebra $\pi(\ba_\a)"$ is of type $\ty{III}$. Therefore, it could be of…

Operator Algebras · Mathematics 2018-06-22 Francesco Fidaleo , Luca Suriano

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

Recently Dabrowski etc. \cite{DL} obtained the metric and Einstein functionals by two vector fields and Laplace-type operators over vector bundles, giving an interesting example of the spinor connection and square of the Dirac operator.…

Differential Geometry · Mathematics 2024-05-21 Jian Wang , Yong Wang , Tong Wu

Almost commutative models provide a framework for Connes' work on the standard model of particle physics. These models are constructed as products of a the canonical spectral triple of a compact connected spin manifold with a finite…

Operator Algebras · Mathematics 2026-03-20 Frederic Latremoliere

We construct spectral triples and, in particular, Dirac operators, for the algebra of continuous functions on certain compact metric spaces. The triples are countable sums of triples where each summand is based on a curve in the space.…

Metric Geometry · Mathematics 2007-06-19 Erik Christensen , Cristina Ivan , Michel L. Lapidus

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

We present a duality between the category of compact Riemannian spin manifolds (equipped with a given spin bundle and charge conjugation) with isometries as morphisms and a suitable "metric" category of spectral triples over commutative…

Operator Algebras · Mathematics 2011-12-30 Paolo Bertozzini , Roberto Conti , Wicharn Lewkeeratiyutkul

We compute $K-theory of noncommutative Bieberbach manifolds, which quotients of a three-dimensional noncommutative torus by a free action of a cyclic group Z_N, N=2,3,4,6.

Quantum Algebra · Mathematics 2018-06-04 Piotr Olczykowski , Andrzej Sitarz

We construct a canonical geometrically realised Connes spectral triple or `Dirac operator' $D\!\!\!/$ from the data of a quantum metric $g\in \Omega^1\otimes_A\Omega^1$ and quantum Levi-Civita bimodule connection, at the pre-Hilbert space…

Quantum Algebra · Mathematics 2023-05-16 Shahn Majid

In the paper, we give four different examples of the rescaled Dirac operator by the perturbation of the function f. Further, based on the trilinear Clifford multiplication by functional of differential one-forms, we compute the spectral…

Differential Geometry · Mathematics 2025-06-09 Tong Wu , Yong Wang

We present about twenty conjectures, problems and questions about flat manifolds. Many of them build the bridges between the flat world and representation theory of the finite groups, hyperbolic geometry and dynamical systems.

Differential Geometry · Mathematics 2010-02-02 Andrzej Szczepanski

While there has been growing interest for noncommutative spaces in recent times, most examples have been based on the simplest noncommutative algebra: [x_i,x_j]=i theta_{ij}. Here we present new classes of (non-formal) deformed products…

High Energy Physics - Theory · Physics 2009-11-07 J. M. Gracia-Bondia , F. Lizzi , G. Marmo , P. Vitale

An orbifold is a Morita equivalence class of a proper {\' e}tale Lie groupoid. A unitary equivalence class of spectral triples over the algebra of smooth invariant functions are associated with any compact spin orbifold. In the case of an…

Differential Geometry · Mathematics 2015-04-07 Antti J. Harju

We present a definition of Riemannian manifold in noncommutative geometry. Using products of unbounded Kasparov modules, we show one can obtain such Riemannian manifolds from noncommutative spin^c manifolds; and conversely, in the presence…

K-Theory and Homology · Mathematics 2015-05-30 Steven Lord , Adam Rennie , Joseph C. Varilly