  R Kerr's Ricci-flat Lorentz 4-manifold was shown by B Carter in 1968 to
support a classically completely integrable system of geodesics; here we
interpret this system in terms of a locally conformally symplectic structure,
which we identify (\S 2.2) using characteristic classes defined by Kerr-Schild
Cartesian coordinates (regarded as a map to the Cayley-Penrose compactification
of Minkowski space). This leads to the definition of an interesting cobordism
category of contact 3-manifolds and 4-dimensional locally conformally
symplectic cobordisms between them.
