Misner has shown that in the scattering of massless wave fields by a Kerr black hole, certain modes are amplified at the expense of the rotational energy of the hole. We show here that the existence of this effect can be deduced from simple considerations based on Hawking's theorem that the area of a black hole can never decrease; no detailed examination of the wave equations is necessary. This new approach also reveals the existence of an analog of the Misner process in which a charged wave field is amplified upon being scattered by a charged black hole with consequent extraction of charge and Coulomb energy from the hole. Additional byproducts of this approach are a concise demonstration of the existence of a spin-spin force between a Kerr black hole and a nearby spinning particle, examples of the transcendence of the conservation laws for baryon and lepton numbers, and an example of a quantum violation of Hawking's theorem. The origin of this violation is discussed.

• Received 19 September 1972

DOI:https://doi.org/10.1103/PhysRevD.7.949