  The computation of the polarized amplitudes and cross section of the
processes $\gamma\nu\to\gamma\gamma \nu$, $\gamma\gamma \to \gamma\nu\bar\nu$
and $\nu\bar\nu \to \gamma\gamma\gamma$ is described. We used an effective
lagrangian approach for energies below the threshold for $e^+e^-$ pair
production and the complete computation at higher energies for application in
supernova dynamics. Leading contributions of physics beyond the SM are also
commented.
