Neutrino-anti-neutrino instability in dense neutrino systems, with applications to the early universe and to supernovae

Understand

We exhibit a new instability that leads to "fast" coherent neutrino-antineutrino mixing in a dense neutrino cloud, arising from the standard four-Fermi interaction induced by Z exchange, and overlooked in the big existing literature on fast processes in this venue.

• It can play an essential role in creation of an abundance of pseudoscalar mesons of mass in the KeV range in the early universe, at temperatures in the range 10-100 MeV.
• Also it can overpower existing calculations in the "neutrino bulb" regions of the supernova cloud.