Effect of the collisional flavor instability on core-collapse supernova models

We explore the effects of the neutrino collisional flavor instability (CFI) based on 1D and 2D corecollapse supernova (CCSN) simulations done using the sophisticated radiation-hydrodynamic code FORNAX. We compare the growth rates of homogeneous CFI (hCFI) modes calculated by numerically solving the multigroup dispersion relation to those calculated using the monochromatic approximation.We find that the widely used monochromatic approximation leads to incorrect growth rates when applied in multigroup scenarios. As opposed to the ∼10⁵ s⁻¹ values given by the monochromatic approximation, the actual growth rates of nonresonance multigroup hCFI are at most ∼200 s⁻¹ in all our models and they are too slow to affect CCSN outcomes. We adopt a Bhatnagar–Gross–Krook flavor conversion scheme in the simulations to include the effects of resonancelike hCFI. We find that the CCSN dynamics and neutrino emission properties are only weakly influenced, and the intrinsic stochasticity due to convection and neutrino-driven turbulence can naturally lead to comparable effects. Hence, our analysis of the nonresonance and resonancelike hCFI into CCSN simulations suggests that the effects of neutrino flavor conversion triggered by hCFI modes are in general small.