Three-dimensional Core-collapse Supernova Simulations with Multidimensional Neutrino Transport Compared to the Ray-by-ray-plus Approximation

Abstract

Abstract Self-consistent, time-dependent supernova (SN) simulations in three spatial dimensions (3D) are conducted with the Aenus-Alcar code, comparing, for the first time, calculations with fully multidimensional (FMD) neutrino transport and the ray-by-ray-plus (RbR+) approximation, both based on a two-moment solver with algebraic M1 closure. We find good agreement between 3D results with FMD and RbR+ transport for both tested grid resolutions in the cases of a 20 M ⊙ progenitor, which does not explode with the employed simplified set of neutrino opacities, and of an exploding 9 M ⊙ model. This is in stark contrast to corresponding axisymmetric (2D) simulations, which confirm previous claims that the RbR+ approximation can foster explosions in 2D, particularly in models with powerful axial sloshing of the stalled shock due to the standing accretion shock instability. However, while local and instantaneous variations of neutrino fluxes and heating rates can still be considerably higher with RbR+ transport in 3D, the time-averaged quantities are very similar to FMD results, because of the absence of a fixed, artificial symmetry axis that channels the flow. Therefore, except for stochastic fluctuations, the neutrino signals and the postbounce evolution of 3D simulations with FMD and RbR+ transport are also very similar, particularly for our calculations with the better grid resolution. Higher spatial resolution clearly has a more important impact than the differences due to the two transport treatments. Our results back up the use of the RbR+ approximation for neutrino transport in 3D SN modeling.