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Generalized superradiant scattering

Mauricio Richartz¹, Silke Weinfurtner^1,2, A. J. Penner¹, and W. G. Unruh¹

¹Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 Canada
²Astrophysics Sector, International School for Advanced Studies, Via Beirut 2-4, 34014 Trieste, Italy and INFN, Sezione di Trieste, Italy USA

Phys. Rev. D 80, 124016 – Published 11 December, 2009

DOI: https://doi.org/10.1103/PhysRevD.80.124016

Abstract

We analyze the necessary and sufficient conditions for the occurrence of superradiance. Starting with a wave equation we examine the possibility of superradiance in terms of an effective potential and boundary conditions. In particular, we show that the existence of an ergoregion is not sufficient; an appropriate boundary condition, e.g. only ingoing group velocity waves at an event horizon, is also crucial. After applying our scheme to the standard examples of superradiance, we show that analogue models of gravity without an event horizon do not necessarily exhibit superradiance. Particularly, we show that the superradiant phenomenon is absent in purely rotating inviscid fluids with vorticity. We argue that there should be a catalogue of superradiant systems that can be found by focusing on the necessary and sufficient conditions outlined below.

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References (19)

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Generalized superradiant scattering

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