Abstract
Neutrinos emitted from a supernova may undergo flavor conversions almost immediately above the core, with possible consequences for supernova dynamics and nucleosynthesis. However, the precise conditions for such fast conversions can be difficult to compute and require knowledge of the full angular distribution of the flavor-dependent neutrino fluxes, that is not available in typical supernova simulations. In this paper, we show that the overall flavor evolution is qualitatively similar to the growth of a so-called `zero mode', determined by the background matter and neutrino densities, which can be reliably predicted using only the second angular moments of the electron lepton number distribution, i.e., the difference in the angular distributions of $\nu_e$ and $\bar{\nu}_e$ fluxes. We propose that this zero mode, which neither requires computing the full Green's function nor a detailed knowledge of the angular distributions, may be useful for a preliminary diagnosis of possible fast flavor conversions in supernova simulations with modestly resolved angular distributions
Highlights
The interior of a supernova (SN) hosts a unique laboratory to probe quantum correlations between neutrinos
We propose that this zero mode, which neither requires computing the full Green’s function nor detailed knowledge of the angular distributions, may be useful for a preliminary diagnosis of possible fast flavor conversions in supernova simulations with modestly resolved angular distributions
The angular distributions are expected to be similar, and we only change the relative weights of the νe and νe fluxes within the range predicted by models exhibiting lepton-emission self-sustained asymmetry (LESA) to get a crossing in electron lepton number (ELN) at vc 1⁄4 0.3, as shown in the right panel of Fig. 3
Summary
The interior of a supernova (SN) hosts a unique laboratory to probe quantum correlations between neutrinos. In a series of papers [4,8,10], Sawyer has pointed out a new mechanism for self-induced flavor conversions called “fast” instabilities These are expected to develop at very short distances, r ≲ Oð1Þ m, from the neutrinosphere and grow with a rate μ, i.e., faster than the usual neutrino oscillations and faster than the relatively. We expect that this method will be useful to scan the different regions of a SN in multidimensional simulations and study the possibility of fast flavor conversions therein.
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