Almost Lie Algebroids and Characteristic Classes

Abstract

Almost Lie algebroids are generalizations of Lie algebroids, when the Jacobiator is not necessarily null. A simple example is given, for which a Lie algebroid bracket or a Courant bundle is not possible for the given anchor, but a natural extension of the bundle and the new anchor allows a Lie algebroid bracket. A cohomology and related characteristic classes of an almost Lie algebroid are also constructed. We prove that these characteristic classes are all pull-backs of the characteristic classes of the base space, as in the case of a Lie algebroid.