The Dirac propagator in the Kerr-Newman metric

We give an alternative proof of the completeness of the Chandrasekhar ansatz for the Dirac equation in the Kerr-Newman metric. Based on this, we derive an integral represen-tation for smooth compactly supported functions which in turn we use to derive an integral representation for the propagator of solutions of the Cauchy problem with initial data in the above class of functions. As a by-product, we also obtain the propagator for the Dirac equation in the Minkowski space-time in oblate spheroidal coordinates. One of the most spectacular predictions of general relativity are black holes which should form when a large mass is concentrated in a sufficiently small volume. The idea of a mass-concentration which is so dense that even light would be trapped goes back to Laplace in the 18th century. Shortly after Einstein developed genera