Fast neutrino flavor conversions near the supernova core with realistic flavor-dependent angular distributions

Understand

It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core.

• Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core.
• We carefully specify the instabilities for evolution in space or time, andfind that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries that produce a crossing between the zenith-angle spectra of $\nu_e$ and ${\bar\nu_e}$.
• Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres.