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We examine the hypothesis that space-time is a product of a continuous four-dimensional manifold times a finite space. A new tensorial notation is developed to present the various constructs of noncommutative geometry. In particular, this…

High Energy Physics - Theory · Physics 2014-11-20 Ali H. Chamseddine , Alain Connes

We analyze strict positivity at the boundary for nonnegative solutions of Robin problems in general (non-smooth) domains, e.g. open sets with rectifiable topological boundaries having finite Hausdorff measure. This question was raised by…

Analysis of PDEs · Mathematics 2022-06-22 Dorin Bucur , Alessandro Giacomini , Mickaël Nahon

We review recent progress in the analytic study of random matrix models suggested by noncommutative geometry. One considers fuzzy spectral triples where the space of possible Dirac operators is assigned a probability distribution. These…

High Energy Physics - Theory · Physics 2022-10-12 Hamed Hessam , Masoud Khalkhali , Nathan Pagliaroli , Luuk Verhoeven

In this paper, a simple proof of the divergence theorem is given by using the Dirac operator and noncommutative residues. Then we extend the divergence theorem to compact manifolds with boundary by the noncommutative residue of the…

Mathematical Physics · Physics 2025-06-24 Jian Wang , Yong Wang

A Dirac operator is presented that will yield a 1+ summable regular even spectral triple for all noncommutative compact surfaces defined as subalgebras of the Toeplitz algebra. Connes' conditions for noncommutative spin geometries are…

Operator Algebras · Mathematics 2020-02-26 Fredy Díaz García , Elmar Wagner

This article surveys recent results aiming at obtaining refined mapping estimates for the X-ray transform on a Riemannian manifold with boundary, which leverage the condition that the boundary be strictly geodesically convex. These…

Analysis of PDEs · Mathematics 2023-09-04 François Monard

In these three lectures we will discuss some fundamental aspects of the theory of self-adjoint extensions of the covariant Laplace-Beltrami and Dirac operators on compact Riemannian manifolds with smooth boundary emphasizing the relation…

Mathematical Physics · Physics 2015-06-05 A. Ibort

We consider a complex Hermitian manifold of complex dimensions four with a Hermitian metric and a Chern connection. It is shown that the action that determines the dynamics of the metric is unique, provided that the linearized Einstein…

High Energy Physics - Theory · Physics 2009-11-11 Ali H. Chamseddine

In this paper, we consider the eigenvalue problem of Dirac operator on a compact Riemannian manifold isometrically immersed into Euclidean space and derive some extrinsic estimates for the sum of arbitrary consecutive $n$ eigenvalues of the…

Differential Geometry · Mathematics 2024-02-23 Lingzhong Zeng

Solids built out of active components can exhibit non-reciprocal elastic coefficients that give rise to non-Hermitian wave phenomena. Here, we investigate non-Hermitian effects present at the boundary of two-dimensional active elastic media…

Soft Condensed Matter · Physics 2020-09-16 Colin Scheibner , William T. M. Irvine , Vincenzo Vitelli

We have obtained the supersymmetric extension of spectral triple which specify a noncommutative geometry(NCG). We assume that the functional space H constitutes of wave functions of matter fields and their superpartners included in the…

High Energy Physics - Theory · Physics 2014-12-31 Satoshi Ishihara , Hironobu Kataoka , Atsuko Matsukawa , Hikaru Sato , Masafumi Shimojo

We construct quantum effective action in spacetime with branes/boundaries. This construction is based on the reduction of the underlying Neumann type boundary value problem for the propagator of the theory to that of the much more…

High Energy Physics - Theory · Physics 2008-11-26 A. O. Barvinsky , D. V. Nesterov

We derive a formula for the gravitational part of the spectral action for Dirac operators on 4-dimensional manifolds with totally anti-symmetric torsion. We find that the torsion becomes dynamical and couples to the traceless part of the…

High Energy Physics - Theory · Physics 2010-11-09 Florian Hanisch , Frank Pfaeffle , Christoph A. Stephan

For a compact connected Riemannian manifold with smooth boundary, we establish an effective procedure, by which we can calculate all the coefficients of the spectral asymptotic formula of the Dirichlet-to-Neumann map associated to the…

Differential Geometry · Mathematics 2025-01-14 Xiaoming Tan

The Einstein-Hilbert action for general relativity is not well posed in terms of the metric $g_{ab}$ as a dynamical variable. There have been many proposals to obtain an well posed action principle for general relativity, e.g., addition of…

General Relativity and Quantum Cosmology · Physics 2017-03-16 Sumanta Chakraborty

On a compact manifold with boundary, the map consisting of the scalar curvature in the interior and the mean curvature on the boundary is a local surjection at generic metrics. Moreover, this result may be localized to compact subdomains in…

Differential Geometry · Mathematics 2026-03-20 Hongyi Sheng

We show how the bosonic spectral action emerges from the fermionic action by the renormalization group flow in the presence of a dilaton and the Weyl anomaly. The induced action comes out to be basically the Chamseddine-Connes spectral…

High Energy Physics - Theory · Physics 2015-05-28 A. A. Andrianov , M. A. Kurkov , Fedele Lizzi

We introduce an invariant of Riemannian geometry which measures the relative position of two von Neumann algebras in Hilbert space, and which, when combined with the spectrum of the Dirac operator, gives a complete invariant of Riemannian…

High Energy Physics - Theory · Physics 2011-04-28 Alain Connes

We examine some noncommutative spherically symmetric spaces in three space dimensions. A generalization of Snyder's noncommutative (Euclidean) space allows the inclusion of the generator of dilations into the defining algebra of the…

High Energy Physics - Theory · Physics 2011-01-28 Sean Murray , Jan Govaerts

We classify and construct all real spectral triples over noncommutative Bieberbach manifolds, which are restrictions of irreducible real equivariant spectral triple over the noncommutative three-torus. We show that in the classical case the…

Quantum Algebra · Mathematics 2019-03-08 Piotr Olczykowski , Andrzej Sitarz