Flavor conversions with energy-dependent neutrino emission and absorption

Abstract

Fast neutrino flavor conversions (FFCs) and collisional flavor instabilities (CFIs) potentially affect the dynamics of core-collapse supernovae and binary neutron star mergers. Under the assumption of homogeneous neutrinos, we investigate effects of neutrino emission and absorption (EA) by matter through both single and multienergy numerical simulations with a physically motivated setup. In our models, FFCs dominate over CFIs in the early phase, while EA secularly and significantly have impact on flavor conversions. They facilitate angular swaps or the full exchange between electron neutrinos (${\ensuremath{\nu}}_{e}$) and heavy-leptonic neutrinos (${\ensuremath{\nu}}_{x}$). As a result, the number density of ${\ensuremath{\nu}}_{x}$ becomes more abundant than the case without EA, despite the fact that the isotropization by EA terminates the FFCs earlier. In the later phase, the system approaches new asymptotic states characterized by EA and CFIs, in which rich energy-dependent structures also emerge. Multienergy effects sustain FFCs and the time evolution of the flavor conversion becomes energy dependent, which are essentially in line with effects of the isoenergetic scattering that we have studied previously. We also find that ${\ensuremath{\nu}}_{x}$ in the high-energy region convert into ${\ensuremath{\nu}}_{e}$ via flavor conversions and then they are absorbed through charged-current reactions, exhibiting the possibility of new path of heating matter.

Topics & Concepts