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In this article, we give a general construction of spectral triples from certain Lie group actions on unital C*-algebras. If the group G is compact and the action is ergodic, we actually obtain a real and finitely summable spectral triple…

Operator Algebras · Mathematics 2013-02-05 Olivier Gabriel , Martin Grensing

We show that smooth isoperimetric profiles are exceptional for real analytic Riemannian manifolds. For instance, under some extra assumption, this can happen only on topological spheres.

Differential Geometry · Mathematics 2012-07-25 Renata Grimaldi , Stefano Nardulli , Pierre Pansu

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

We classify the twists of almost commutative spectral triples that keep the Hilbert space and the Dirac operator untouched. The involved twisting operator is shown to be the product of the grading of a manifold by a finite dimensional…

Mathematical Physics · Physics 2021-12-14 Manuele Filaci , Pierre Martinetti

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

A class of real spectral triples that are similar in structure to a Riemannian manifold but have a finite-dimensional Hilbert space is defined and investigated, determining a general form for the Dirac operator. Examples include fuzzy…

Mathematical Physics · Physics 2015-09-02 John W. Barrett

We show the existence of nonsymmetric homogeneous spin Riemannian manifolds whose Dirac operator is like that on a Riemannian symmetric spin space. Such manifolds are exactly the homogeneous spin Riemannian manifolds $(M,g)$ which are…

Differential Geometry · Mathematics 2016-02-10 P. M. Gadea , José C. González-Dávila , José A. Oubiña

The space of all Riemannian metrics on a smooth second countable finite dimensional manifold is itself a smooth manifold modeled on the space of symmetric (0,2)-tensor fields with compact support. It carries a canonical Riemannian metric…

Differential Geometry · Mathematics 2008-02-03 Olga Gil-Medrano , Peter W. Michor

The notion of a spectral geometry on a compact metric space X is introduced. This notion serves as a discrete approximation of X motivated by the notion of a spectral triple from non-commutative geometry. A set of axioms charaterising…

Operator Algebras · Mathematics 2017-11-01 Sergei Buyalo

We give a simple geometric characterization of isospectral orbifolds covered by spheres, complex projective spaces and the quaternion projective line having cyclic fundamental group. The differential operators considered are…

Differential Geometry · Mathematics 2016-07-20 Emilio A. Lauret

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

In this paper we continue the study of spectral properties of Laplacians associated with an arbitrary smooth distribution on a compact manifold, initiated in a previous paper. Under assumption that the singular foliation generated by the…

Differential Geometry · Mathematics 2020-12-08 Yuri A. Kordyukov

The spectral propinquity is a distance, up to unitary equivalence, on the class of metric spectral triples. We prove in this paper that if a sequence of metric spectral triples converges for the propinquity, then the spectra of the Dirac…

Operator Algebras · Mathematics 2024-07-15 Frederic Latremoliere

Having in view the study of a version of Gel'fand-Neumark duality adapted to the context of Alain Connes' spectral triples, in this very preliminary review, we first present a description of the relevant categories of geometrical spaces,…

Operator Algebras · Mathematics 2014-09-05 Paolo Bertozzini , Fred Jaffrennou

In this note we study the spectrum and the Waelbroeck spectrum of the derivative operator composed with isomorphic multiplication oper

Functional Analysis · Mathematics 2023-01-24 Enrique Jordá

We extend the isospectral deformations of Connes, Landi and Dubois-Violette to the case of Riemannian spin manifolds carrying a proper action of the noncompact abelian group $R^l$. Under deformation by a torus action, a standard formula…

High Energy Physics - Theory · Physics 2007-05-23 Victor Gayral , Bruno Iochum , Joseph C. Varilly

We introduce the notion of a manifold admitting a simple compact Cartan 3-form $\om^3$. We study algebraic types of such manifolds specializing on those having skew-symmetric torsion, or those associated with a closed or coclosed 3-form…

Differential Geometry · Mathematics 2013-04-04 Hong Van Le

We construct a Connes spectral triple or `Dirac operator' on the non-reduced fuzzy sphere $C_\lambda[S^2]$ as realised using quantum Riemannian geometry with a central quantum metric $g$ of Euclidean signature and its associated quantum…

Quantum Algebra · Mathematics 2022-02-09 Evelyn Lira-Torres , Shahn Majid

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

Inspired by the role geometric structures play in our understanding of surfaces and three-manifolds, and Berger's observation that a surface of constant sectional curvature is determined up to local isometry by its Laplace spectrum, we…

Differential Geometry · Mathematics 2019-05-29 Samuel Lin , Benjamin Schmidt , Craig Sutton