The many faces of superradiance

J. Bekenstein, M. Schiffer

Research output: Contribution to journalArticlepeer-review

118 Scopus citations

Abstract

Inertial motion superradiance, the emission of radiation by an initially unexcited system moving inertially but superluminally through a medium, has long been known. Rotational superradiance, the amplification of radiation by a rotating rigid object, was recognized much later, principally in connection with black hole radiances. Here we review the principles of inertial motion superradiance and prove thermodynamically that the Ginzburg-Frank condition for superradiance coincides with the condition for superradiant amplification of already existing radiation. Examples we cite include a new type of black hole superradiance. We correct Zel’dovich’s thermodynamic derivation of the Zel’dovich-Misner condition for rotational superradiance by including the radiant entropy in the bookkeeping. We work out in full detail the electrodynamics of a Zel’dovich rotating cylinder, including a general electrodynamic proof of the Zel’dovich-Misner condition, and explicit calculations of the superradiant gain for both types of polarization. Contrary to Zel’dovich’s pessimistic conclusion we conclude that, if the cylinder is surrounded by a dielectric jacket and the whole assembly is placed inside a rotating cavity, the superradiance is measurable in the laboratory.

Original languageEnglish
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume58
Issue number6
DOIs
StatePublished - 1998
Externally publishedYes

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