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arXiv · 2605.12392

On the Geometry of Cotton Gravity

Giulio Colombo·Filippo Mastropietro·Marco Rigoli
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Abstract

We analyze the geometry of the field equations of Cotton gravity (for a quite general energy-momentum tensor) on a static space-time. In particular, we describe the local structure of the spatial Riemannian factor. This structure, that we call Cotton-$\varphi$-perfect fluid (C-$\varphi$-PF, for short) is a generalization to the regime of Cotton Gravity of the recently introduced notion of $\varphi$-static perfect fluid space-time ($\varphi$-SPFST). After discussing the variational origin of this system, we provide sufficient conditions for a C-$\varphi$-PF to reduce to a $\varphi$-SPFST. We also study the geometry of the level sets of the lapse function $f$ and we provide a rigidity result for C-$\varphi$-PFs under some curvature conditions. The role that Codazzi tensors hold in this theory is highlighted.

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Giulio Colombo, Filippo Mastropietro, Marco Rigoli. 2026-05-12. On the Geometry of Cotton Gravity. https://arxiv.org/abs/2605.12392

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