Superradiance is amplification of a scattered wave by extracting rotational or other available conserved energy from a background. For a rotating Kerr black hole, a bosonic mode of frequency and azimuthal integer can have negative horizon Killing-energy flux when . The reflected energy can then exceed the incident energy. A stationary Killing flow need not define a globally positive particle energy.
Articles by others on the same topic
Superradiance is a phenomenon that occurs in quantum mechanics and quantum field theory, typically associated with systems of particles or fields that can coherently amplify energy or particles under certain conditions. The most common context for discussing superradiance is in relation to rotating black holes, particularly the Kerr black hole.