The Effect of the Fast-Flavor Instability on Core-Collapse Supernova Models: II. Quasi-Equipartition and the Impact of Various Angular Reconstruction Methods

In this work, we explore in a consistent fashion the effects of fast flavor conversion (FFC) in 1D and 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 is only minor ways. We also present a ``quasi-equipartition’’ approximation which can be used to estimate the FFC-altered neutrino properties by post-processing 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.