The many faces of superradiance
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 GinzburgFrank 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'dovichMisner 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'dovichMisner 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.
 Publication:

Physical Review D
 Pub Date:
 September 1998
 DOI:
 10.1103/PhysRevD.58.064014
 arXiv:
 arXiv:grqc/9803033
 Bibcode:
 1998PhRvD..58f4014B
 Keywords:

 42.50.Fx;
 04.70.Bw;
 03.50.De;
 41.60.Bq;
 Cooperative phenomena in quantum optical systems;
 Classical black holes;
 Classical electromagnetism Maxwell equations;
 Cherenkov radiation;
 General Relativity and Quantum Cosmology;
 Astrophysics;
 Physics  Atomic Physics;
 Physics  Optics
 EPrint:
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