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zbMATH Open
Article
Data sources: zbMATH Open
Journal of Mathematical Physics
Article . 1999 . Peer-reviewed
Data sources: Crossref
https://dx.doi.org/10.48550/ar...
Article . 1998
License: arXiv Non-Exclusive Distribution
Data sources: Datacite
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Discrete Riemannian geometry

Authors: Folkert Müller-Hoissen; Aristophanes Dimakis;

Discrete Riemannian geometry

Abstract

Within a framework of noncommutative geometry, we develop an analog of (pseudo-) Riemannian geometry on finite and discrete sets. On a finite set, there is a counterpart of the continuum metric tensor with a simple geometric interpretation. The latter is based on a correspondence between first order differential calculi and digraphs (the vertices of the latter are given by the elements of the finite set). Arrows originating from a vertex span its (co)tangent space. If the metric is to measure length and angles at some point, it has to be taken as an element of the left-linear tensor product of the space of 1-forms with itself, and not as an element of the (nonlocal) tensor product over the algebra of functions, as considered previously by several authors. It turns out that linear connections can always be extended to this left tensor product, so that metric compatibility can be defined in the same way as in continuum Riemannian geometry. In particular, in the case of the universal differential calculus on a finite set, the Euclidean geometry of polyhedra is recovered from conditions of metric compatibility and vanishing torsion. In our rather general framework (which also comprises structures which are far away from continuum differential geometry), there is, in general, nothing like a Ricci tensor or a curvature scalar. Because of the nonlocality of tensor products (over the algebra of functions) of forms, corresponding components (with respect to some module basis) turn out to be rather nonlocal objects. But one can make use of the parallel transport associated with a connection to “localize” such objects, and in certain cases there is a distinguished way to achieve this. In particular, this leads to covariant components of the curvature tensor which allow a contraction to a Ricci tensor. Several examples are worked out to illustrate the procedure. Furthermore, in the case of a differential calculus associated with a hypercubic lattice we propose a new discrete analogue of the (vacuum) Einstein equations.

Related Organizations
Keywords

Einstein equations, High Energy Physics - Theory, Mathematics - Differential Geometry, High Energy Physics - Lattice (hep-lat), FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Mathematical Physics (math-ph), polyhedra, Ricci tensor, Lattice gravity, Regge calculus and other discrete methods in general relativity and gravitational theory, Global Riemannian geometry, including pinching, General Relativity and Quantum Cosmology, Global differential geometry of Lorentz manifolds, manifolds with indefinite metrics, High Energy Physics - Lattice, High Energy Physics - Theory (hep-th), Differential Geometry (math.DG), FOS: Mathematics, Noncommutative geometry in quantum theory, Methods of noncommutative geometry in general relativity, noncommutative geometry, Noncommutative global analysis, noncommutative residues, Mathematical Physics

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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
42
Average
Top 10%
Top 10%
Green
bronze