Super-radiance and flux conservation

Understand

The theoretical foundations of the phenomenon known as super-radiance still continues to attract considerable attention.

• Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate some significant confusion.
• Part of the confusion arises from the fact that super-radiance in a quantum field theory [QFT] context is not the same as super-radiance (super-fluorescence) in some condensed matter contexts; part of the confusion arises from traditional but sometimes awkward normalization conventions, and part is due to sometimes unnecessary confusion between fluxes and probabilities.
• We shall argue that the key point underlying the effect is flux conservation, (and, in the presence of dissipation, a controlled amount of flux non-conservation), and that attempting to phrase things in terms of reflection and transmission probabilities only works in the absence of super-radiance.