A Jacobi structure J on a line bundle L → M is weakly regular if the sharp map J ♯ : J 1 L → DL has constant rank. A generalized contact bundle with regular Jacobi structure possess a transverse complex structure. Paralleling the work of Bailey in generalized complex geometry, we find condition on a pair consisting of a regular Jacobi structure and an transverse complex structure to come from a generalized contact structure. In this way we are able to construct interesting examples of generalized contact bundles. As applications: 1) we prove that every 5dimensional nilmanifold is equipped with an invariant generalized contact structure, 2) we show that, unlike the generalized complex case, all contact bundles over a complex manifold possess a compatible generalized contact structure. Finally we provide a counterexample presenting a locally conformal symplectic bundle over a generalized contact manifold of complex type that do not possess a compatible generalized contact structure. * jschnitzer@unisa.it
Preliminaries and NotationThis introductory section is divided into two parts: first we recall the Atiyah algebroid of a vector bundle and the corresponding Der-complex with applications to contact and Jacobi geometry. Afterwards, we introduce the arena for generalized geometry in odd dimensions, the omni-Lie algebroids, and give a quick reminder of generalized contact bundles together with the properties we will need 2 afterwards.
The Atiyah algebroid and the Der-complexThe notions of Atiyah algebroid of a vector bundle and the associated Der-complex are known and are used in many other situations. This section is basically meant to fix notation. A more complete introduction to this can be found in [17], which also discusses the notion of Dirac structures on the omni-Lie algebroid of line bundles in more detail, nevertheless the notion of Omni-Lie algebroids was first defined in [5], in order to study Lie algebroids and local Lie algebra structures on vector bundles.for a necessarily unique X ∈ Γ ∞ (T M ).Remark 2.2 Derivations of a vector bundle form a subspace of the first order differential operators from E to itself. Moreover, if the vector bundle has rank one then each differential operator is a derivation. Lemma 2.3 Let E → M be a vector bundle. The derivations of of E → M are the sections of a Lie algebroid DE → M . The Lie bracket of Γ ∞ (DE) is the commutator. An element in the fiber DThe Atiyah algebroid fits into the following exact sequence of Lie algebroids, which is called the Spencer sequence,where the Lie algebroid structure of End(E) is the (pointwise) commutator and the trivial anchor. The first arrow is given by the inclusion. With this we see immediatly that rank(DE) = rank(E) 2 + dim(M ).We assign a vector bundle E → M to a Lie algebroid DE → M . A natural question is: is this assignment functorial? In fact it is not, unless we restrict the category of vector bundles by just taking regular vector bundle morphisms, i.e. vector bundle morphisms which are fiber-wise invertible. Note that a regula...