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Causal fermion systems and Riemannian fermion systems are proposed as a framework for describing non-smooth geometries. In particular, this framework provides a setting for spinors on singular spaces. The underlying topological structures…

Mathematical Physics · Physics 2019-05-06 Felix Finster , Niky Kamran

We present the notion of temporal Lorentzian spectral triple which is an extension of the notion of pseudo-Riemannian spectral triple with a way to ensure that the signature of the metric is Lorentzian. A temporal Lorentzian spectral triple…

Mathematical Physics · Physics 2014-09-11 Nicolas Franco

Non-Hermitian systems have been discussed mostly in the context of open systems and nonequilibrium. Recent experimental progress is much from optical, cold-atomic, and classical platforms due to the vast tunability and clear identification…

Mesoscale and Nanoscale Physics · Physics 2024-01-25 Xiao-Xiao Zhang , Naoto Nagaosa

We present a new example of a finite-dimensional noncommutative manifold, namely the noncommutative cylinder. It is obtained by isospectral deformation of the canonical triple associated to the Euclidean cylinder. We discuss Connes'…

Mathematical Physics · Physics 2008-11-26 W. D. van Suijlekom

Spin textures, i.e., the distribution of spin polarization vectors in reciprocal space, exhibit diverse patterns determined by symmetry constraints, resulting in a variety of spintronic phenomena. Here, we propose a universal theory to…

Materials Science · Physics 2024-09-24 Yuntian Liu , Jiayu Li , Pengfei Liu , Qihang Liu

We consider a $3$-dimensional differentiable manifold with two circulant structures -- a Riemannian metric and an additional structure, whose third power is the identity. The structure is compatible with the metric such that an isometry is…

Differential Geometry · Mathematics 2017-03-31 Georgi Dzhelepov

We introduce the $R$ cut-off covering spectrum and the cut-off covering spectrum of a complete length space or Riemannian manifold. The spectra measure the sizes of localized holes in the space and are defined using covering spaces called…

Metric Geometry · Mathematics 2010-02-05 Christina Sormani , Guofang Wei

This paper proposes a new notion of smoothness of algebras, termed differential smoothness, that combines the existence of a top form in a differential calculus over an algebra together with a strong version of the Poincar\'e duality…

Quantum Algebra · Mathematics 2015-05-07 Tomasz Brzeziński , Andrzej Sitarz

A Riemannian manifold is a called a good rational expander in dimension $i$ if every $i$-cycle bounds a rational $i+1$-chain of comparatively small volume. We construct 3-manifolds which are good expanders in all dimensions. On the other…

Geometric Topology · Mathematics 2024-05-09 Jonathan Zung

Suppose $M$ is a closed, connected, orientable, \irr\ \3m\ such that $G=\pi_1(M)$ is infinite. One consequence of Thurston's geometrization conjecture is that the universal covering space $\widetilde{M}$ of $M$ must be \homeo\ to $\RRR$.…

Geometric Topology · Mathematics 2016-09-06 Robert Myers

The space of all non degenerate bilinear structures on a manifold $M$ carries a one parameter family of pseudo Riemannian metrics. We determine the geodesic equation, covariant derivative, curvature, and we solve the geodesic equation…

Differential Geometry · Mathematics 2016-09-06 Olga Gil-Medrano , Peter W. Michor , Martin Neuwirther

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

It is shown that every bundle $\varSigma\to M$ of complex spinor modules over the Clifford bundle $\Cl(g)$ of a Riemannian space $(M,g)$ with local model $(V,h)$ is associated with an lpin ("Lipschitz") structure on $M$, this being a…

Differential Geometry · Mathematics 2007-05-23 Thomas Friedrich , Andrzej Trautman

Almost-flat manifolds were defined by Gromov as a natural generalisation of flat manifolds and as such share many of their properties. Similarly to flat manifolds, it turns out that the existence of a spin structure on an almost-flat…

Algebraic Topology · Mathematics 2018-04-12 Rafał Lutowski , Nansen Petrosyan , Andrzej Szczepański

In this survey paper on commutative ring spectra we present some basic features of commutative ring spectra and discuss model category structures. As a first interesting class of examples of such ring spectra we focus on (commutative)…

Algebraic Topology · Mathematics 2017-10-09 Birgit Richter

In this paper I discuss connections between the noncommutative geometry approach to the standard model on one side, and the internal space coming from strings on the other. The standard model in noncommutative geometry is described via the…

High Energy Physics - Theory · Physics 2008-11-26 Fedele Lizzi

We define a symplectic structure on the space of non parametrized loops in $G_2$ manifold. We also develop some basics of intersection theory of Lagrangian submanifolds.

Symplectic Geometry · Mathematics 2007-05-23 M. V. Movshev

We classify spin structures on the noncommutative torus, and find that the noncommutative n-torus has 2^n spin structures, corresponding to isospectral deformations of spin structures on the commutative n-torus. For n>3 the classification…

Operator Algebras · Mathematics 2011-12-30 Jan Jitse Venselaar

This is a survey of the inverse spectral problem on (mainly compact) Riemannian manifolds, with or without boundary. The emphasis is on wave invariants: on how wave invariants have been calculated and how they have been applied to concrete…

Spectral Theory · Mathematics 2011-11-10 Steve Zelditch

It was recently pointed out by E. Witten that for a D-brane to consistently wrap a submanifold of some manifold, the normal bundle must admit a Spin^c structure. We examine this constraint in the case of type II string compactifications…

High Energy Physics - Theory · Physics 2009-10-31 Robert L. Bryant , Eric R. Sharpe