Pairwise Neutrino Flavor Conversion in Supernovae: Quantum Kinetics and Astrophysical Implications

Abstract Neutrino flavor conversion is one of the major uncertainties in the numerical modeling of explosive astrophysical events, such as core-collapse supernovae and binary neutron-star mergers, which are promising sources of detectable gravitational waves. In this proceedings article, we discuss the pairwise nature and quasi-steady states of collective neutrino flavor conversion, induced by neutrino self-interactions and incoherent collisions. Using numerical simulations based on the quantum kinetic equation, we show that the neutrino system evolves asymptotically toward a quasi-steady states through turbulence-like cascades and collisional processes with background matter. The asymptotic states are constrained by pairwise flavor conversion, which preserves the electron- and heavy-leptonic flavor lepton numbers, while allowing nontrivial species-dependent angular and spectral distributions. Our results indicate that the impact of flavor conversion cannot be modeled simply by assuming complete flavor equipartition. Rather, effective modeling should account for the rich energy and angular structures of the post-conversion states. We discuss possible implications for neutrino heating and cooling near the proto-neutron star and for the associated hydrodynamic and gravitational-wave signals.