Superradiance was first described by Dicke in 1954 in this paper (official link). If you are a laser / optical physics expert, then you already know all about it. For everyone else, this post is an introductory tutorial.
Motivation: What does superradiance have to do with cold fusion? Well, I’m gearing up to discuss Peter Hagelstein’s “spin-boson model” theory of cold fusion. This theory says that the 24MeV of energy from D+D→⁴He fusion goes more-or-less directly into exciting a billion or so phonons (all of them in a single phonon mode, i.e. all at the same frequency, wavelength, etc.). Normally, this process would be extremely unlikely. However, there are two famous effects that increase the probability of transferring energy to an oscillation mode: Dicke superradiance and stimulated emission. Accordingly, the spin-boson model relies very heavily on both of these principles.
Since it’s impossible to thoroughly understand the spin-boson model without understanding superradiance, and since I couldn’t find a suitable description online, I wrote out this post. Buckle your seatbelts, let’s do some physics!