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arXiv · 2312.11558

A unified-description of curvature, torsion, and non-metricity of the metric-affine geometry with the M\"{o}bius representation

Kyosuke Tomonari
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Abstract

We establish the mathematical fundamentals for a unified description of curvature, torsion, and non-metricity 2-forms in the way extending the so-called M\"{o}bius representation of the affine group, which is the method to convert the semi-direct product into the ordinary matrix product, to revive the fertility of gauge theories of gravity. First of all, we illustrate the basic concepts for constructing the metric-affine geometry. Then the curvature and torsion 2-forms are described in a unified manner by using the Cartan connection of the M\"{o}bius representation of the affine group. In this unified-description, the curvature and torsion are derived by Cartan's structure equation with respect to a common connection 1-form. After that, extending the M\"{o}bius representation, the dilation and shear 2-forms, or equivalently, the non-metricity 2-form, are introduced in the same unified manner. Based on the unified-description established in this paper, introducing a new group parametrization and applying the In\"{o}n\"{u}-Wigner group contraction to the full theory, the relationships among symmetries, geometric quantities, and geometries are investigated with respect to the three gauge groups: the metric-affine group and its extension, and an extension of the (anti)-de Sitter group in which the non-metricity exists. Finally, possible applications to theories of gravity are briefly discussed.

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Kyosuke Tomonari. 2023-12-17. A unified-description of curvature, torsion, and non-metricity of the metric-affine geometry with the M\"{o}bius representation. https://doi.org/10.1142/s021988782450333x

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