Photon-neutrino interactions

The cross sections for the processes \gamma \nu --> \gamma\gamma \nu, \gamma\gamma -->\gamma\nu\bar{\nu} and \nu\bar{\nu} -->\gamma\gamma\gamma are calculated with the aid of an effective Lagrangian derived from the Standard model. These cross sections are shown to be much larger than the elastic cross section \sigma(\gamma\nu --> \gamma\nu) for photon energies $\omega >1$ keV. Possible astrophysical implications are discussed.