Published online by Cambridge University Press: 26 February 2010
§1. With respect to coordinates {z, x1, …, xq+1, …, x2q} a contact transformation is a local diffeomorphism of ℝ2q+1, which preserves the 1-form
up to multiplication by a non-zero real valued function. The family of such maps contains identities, inverses and admits a partial composition law; denote it by the contact pseudogroup. Passing to germs of local diffeomorphisms we obtain a topological groupoid Γ2q+1, ω, to which by any of several constructions, see [1] for example, there corresponds a classifying space BΓ2q+1, ω, By analogy with BΓq this space classifies codimension (2q + l)-foliations, which locally admit a contact structure normal to the leaves. In particular, at least when q is odd, the structural group of the normal bundle reduces to Uq. We shall be most interested in the case, when the foliation is by points, and the underlying manifold M2q+1 admits a global 1-form co such that