Mixed Dark Matter from Neutrino Lasing

We investigate the production of dark matter with non-standard momentum distributions arising from the decay of a relativistic massive neutrino into a lighter fermion and boson H$\rightarrow$F$+$B. We develop the Boltzmann equations for this process, paying particular attention to spin polarisation effects. Such decays can, under certain circumstances, lead to a process of runaway stimulated decays or `neutrino-lasing' resulting, for suitable boson mass, in the production of mixed-dark-matter. We discuss a number of variations on the model; we show how the yield of cold particles can be increased by a simple modification to our original proposal. We discuss the singlet-majoron model as a possible framework for these decays.