  Recently, Dicus and Repko computed nu gamma --> nu gamma gamma for energies
below the threshold for e^{+}e^{-} pair production. They found across section
on the order of 10^{-52} omega ^{gamma} with gamma =10, where omega is the CMS
energy of one of the initial particles in MeV. Cross sections for the crossed
processes are the same to factors of order one. This note investigates the
extent to which these processes could, if their result extrapolates past 1 MeV:
affect supernova dynamics; cut off the energy distribution of very high energy
cosmic photons and neutrinos; and possibly give rise to an observable gamma
signal from scattering of neutrinos from one supernova by those of a second
supernova close in space and time. We also estimate, from Supernova 1987A,
that, in the region above a few MeV, gamma must fall below 8.4.
