# Does there exist a notion that generalizes a black body to include other emission processes than electromagnetic ones?

A black body by definition is a perfect absorber for all incident electromagnetic radiation. It isotropically emits electromagnetic radiation whose spectral distribution only depends on the temperature.

When we go to higher temperatures, other radiative-like processes will start to play a role as well, like neutrino emission, production of high energy electrons and positrons etc.

Is there a generalized notion of a black body where these other forms of energy emission are taken into account? Do the characteristics of the emitted matter and radiation still only depend on the temperature?

• If you're talking about blackbody radiation, the usual notion of it is perfectly good at describing all of those things, in fact I'm not aware of any regime in which it breaks down. – Al Nejati Nov 1 '18 at 2:21
• @AlNejati blackbody radiation is specifically only about electromagnetic radiation. What about non-EM processes? – doetoe Nov 1 '18 at 3:41

Note that the fundamental charge $$e$$ does not appear in Planck’s blackbody formula. In other words, blackbody radiation of massless bosons does not depend on how strongly they interact with matter! This is because for a blackbody we assume that any incident photons are completely absorbed. If the blackbody is assumed to be sufficiently “thick”, it can absorb them regardless of how strongly or weakly they interact with it.