Recently , Dicus and Repko computed \nu \gamma \rightarrow \nu \gamma \gamma for energies below the threshold for e ^ { + } e ^ { - } pair production .
They found a cross 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 .