The Effect of the Fast-flavor Instability on Core-collapse Supernova Models. II. Quasi-equipartition and the Impact of Various Angular Reconstruction Methods

Abstract In this work, we explore the effects of fast-flavor conversion (FFC) in one-dimensional (1D) and two-dimensional (2D) core-collapse supernova (CCSN) simulations. In addition, we investigate the impact of various angular reconstruction methods and compare the “3-species” and “4-species” neutrino transport schemes. We find that the FFC effects are insensitive to the different methods tested and that the FFC alters supernova hydrodynamics in only minor ways. We also present a “quasi-equipartition” approximation that can be used to estimate the FFC-altered neutrino properties by postprocessing the neutrino signals extracted from no-oscillation CCSN simulations. The relative errors in neutrino number and energy luminosities of this phenomenological method are less than 2% for 1D models and less than 10% for 2D models. This method provides a simple way to include the effects of FFC on neutrino signals without implementing a complex and expensive FFC scheme or redoing simulations.