Almost commutative versions of Lie algebroids?

board In a preprint `Almost Commutative Q-algebras and Derived brackets , I describe how one can in part generalise the notion of Lie algebroid using Vaintrob’s understanding interms of Q-manifolds [1].

A question that I posed to myself a while ago was if the `super-understanding’ of Lie algebroids in terms of a graded supermanifold equipped with a homological vector field can be generalised to the noncommutative world. Lie–Rinehart pairs have long been understood as the algebraic counterpart to Lie algebroids and offer a direct route to the noncommutative world. However, the idea is to start with Vaintrob’s picture of Lie algebroids. The full problem in the setting of noncommutative geometry seems not to be so tractable. However, the problem in the context of almost commutative geometry (see [2]) has now been tackled.

It turns out that almost commutative algebras, loosely algebras in which elements `almost’ commute, i.e., ab = k ba for some number k, one can mimic the classical case closely. In particular, almost commutativity is close enough to commutativity or supercommutativity (things commute up to signs), that one can make sense of non-negatively graded almost commutative algebras. Philosophically, such algebras are thought of as the total spaces of some `almost commutative vector bundles’ following the ethos of Grabowski & Rotkiewicz [3] (and Th. Voronov in several of his papers). We can make sense of homological derivations of weight one and push the derive bracket formalism of Kosmann-Schwarzbach [4] through and construct a kind of Lie bracket and anchor map. In short, with a little care, all the basic ideas of describing Lie algebroids in terms of supergeometry can be generalised to almost commutative geometry.

While the results are essentially the expected ones, this shows that ideas from graded and supergeometry, including derived brackets, can be applied to specific versions of noncommutative geometries. We hope to further explore this in the near future.

I thank Prof. Tomasz Brzezinski and Prof. Richard Szabo for their advice with parts of this preprint.

[1] Vaĭntrob, A. Yu. Lie algebroids and homological vector fields, Russian Math. Surveys 52 (1997), no. 2, 428–429

[2] Bongaarts, P. J. M. & Pijls, H. G. J. Almost commutative algebra and differential calculus on the quantum hyperplane, J. Math. Phys. 35 (1994), no. 2, 959–970.

[3] Grabowski, J. & Rotkiewicz, M. Graded bundles and homogeneity structures, J. Geom. Phys. 62 (2012), no. 1, 21–36.

[4] Kosmann-Schwarzbach, Y. Derived brackets, Lett. Math. Phys. 69 (2004), 61–87.