Multi-dimensional Features of Neutrino Transfer in Core-Collapse Supernovae

Abstract

We study the multi-dimensional properties of neutrino transfer inside supernova cores by solving the Boltzmann equations for neutrino distribution functions in genuinely six dimensional (6D) phase space. Adopting representative snapshots of the post-bounce core from other supernova simulations in three dimensions, we solve the temporal evolutions to stationary states of neutrino distribution functions by our Boltzmann solver. Taking advantage of the multi-angle and multi-energy feature realized by the S${}_n$ method in our code, we reveal the genuine characteristics of spatially three dimensional (3D) neutrino transfer such as non-radial fluxes and non-diagonal Eddington tensors. In addition, we assess the ray-by-ray approximation, turning off the lateral-transport terms in our code. We demonstrate that the ray-by-ray approximation tends to propagate fluctuations in thermodynamical states around the neutrino-sphere along each radial ray and overestimate the variations between the neutrino distributions on different radial rays. We find that the difference in the densities and fluxes of neutrinos between the ray-by-ray approximation and the full Boltzmann transport becomes ~20%, which is also the case for the local heating rate, whereas the volume-integrated heating rate in the Boltzmann transport is found to be only slightly larger (~2%) than the counterpart in the ray-by-ray approximation due to cancellation among different rays. These results suggest that we had better assess carefully the possible influences of various approximations in the neutrino transfer employed in the current simulations on supernova dynamics. Detailed information on the angle and energy moments of neutrino distribution functions will be profitable for the future development of numerical methods in neutrino-radiation hydrodynamics.

82 pages, 39 figures, revised version accepted for publication in ApJ

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• Anisotropic emission of neutrino and gravitational-wave signals from rapidly rotating core-collapse supernovae
• A Detailed Comparison of Multi-Dimensional Boltzmann Neutrino Transport Methods in Core-Collapse Supernovae
• Impacts of Rotation on Three-dimensional Hydrodynamics of Core-collapse Supernovae
• Comparing treatments of weak reactions with nuclei in simulations of core-collapse supernovae
• Simulations of the Early Post-Bounce Phase of Core-Collapse Supernovae in Three-Dimensional Space with Full Boltzmann Neutrino Transport
• Gravitational-wave Signals From Three-dimensional Supernova Simulations With Different Neutrino-Transport Methods
• Modeling Core-Collapse Supernovae Gravitational-Wave Memory in Laser Interferometric Data
• Properties of neutrino transfer in a deformed remnant of neutron star merger
• Two- and Three-Dimensional Multi-Physics Simulations of Core Collapse Supernovae: A Brief Status Report and Summary of Results from the "Oak Ridge" Group