Foundations of Noncommutative Carrollian Geometry via Lie-Rinehart Pairs
Andrew James Bruce
TL;DR
This work addresses the problem of formulating Carrollian geometry in noncommutative settings by developing the theory on almost commutative algebras using ρ-Lie-Rinehart pairs as algebraic analogues of Lie algebroids. The authors define Carrollian ρ-Lie-Rinehart pairs with a degenerate metric whose kernel is a free cyclic submodule, and they introduce Carroll distributions as the image of the anchor, proving their involutivity and foliated structure. They construct metric-compatible ρ-connections, derive curvature and torsion as ρ-tensors, and provide a Koszul-type formula in the non-degenerate case, establishing a path to Levi-Civita-type results in this framework. Two explicit toy models—the extended quantum plane and the noncommutative 2-torus—demonstrate Carrollian structures and compatible connections, offering a rigorous platform for noncommutative Carrollian physics and potential links to flat-space holography and condensed-matter applications.
Abstract
Carrollian manifolds offer an intrinsic geometric framework for the physics in the ultra-relativistic limit. The recently introduced Carrollian Lie algebroids are generalised to the setting of $ρ$-commutative geometry, (also known as almost commutative geometry), where the underlying algebras commute up to a numerical factor. Via $ρ$-Lie-Rinehart pairs, it is shown that the foundational tenets of Carrollian geometry have analogous statements in the almost commutative world. We explicitly build two toy examples: we equip the extended quantum plane and the noncommutative $2$-torus with Carrollian structures. This opens up the rigorous study of noncommutative Carrollian geometry via almost commutative geometry.
