Neutrino Flavor Spin Waves From Supernovae

In the first ~10 seconds of a core-collapse supernova explosion, the nascent neutron star emits copious amounts of neutrinos. The flavor evolution paradigm of these neutrinos are different from vacuum oscillations or MSW flavor transformation. Numerical calculations have shown that supernova neutrinos can exhibit stepwise swapping between the energy spectra of neutrinos with different initial flavors. The phenomenon of stepwise swapping of neutrino energy spectra is explained by the adiabatic/precession solution of the equations dictating collective neutrino oscillations. Arising from a symmetry in the equations of motion of neutrino flavor evolution, this solution describes a "flavor spin wave" propagating with supernova neutrinos.