A New Multi-Energy Neutrino Radiation-Hydrodynamics Code in Full General Relativity and Its Application to Gravitational Collapse of Massive Stars

TL;DR

This paper introduces a comprehensive multi-energy neutrino radiation-hydrodynamics code in full general relativity for modeling massive stellar core-collapse, demonstrating its accuracy through standard tests and comparison with existing methods.

Contribution

The paper presents a novel multi-dimensional GR radiation-hydrodynamics code with spectral neutrino transport and advanced neutrino interaction modeling, validated against analytical solutions and previous simulations.

Findings

Code accurately reproduces analytical solutions for gravitational redshift and Doppler shift.

Performs well in simulating core-collapse, bounce, and shock-stall phases of a 15Msun star.

Identifies resolution limitations in postbounce phase, guiding future computational improvements.

Abstract

We present a new multi-dimensional radiation-hydrodynamics code for massive stellar core-collapse in full general relativity (GR). Employing an M1 analytical closure scheme, we solve spectral neutrino transport of the radiation energy and momentum based on a truncated moment formalism. Regarding neutrino opacities, we take into account a baseline set in state-of-the-art simulations, in which inelastic neutrinoelectron scattering, thermal neutrino production via pair annihilation and nucleonnucleon bremsstrahlung are included. While the Einstein field equations and the spatial advection terms in the radiation-hydrodynamics equations are evolved explicitly, the source terms due to neutrino-matter interactions and energy shift in the radiation moment equations are integrated implicitly by an iteration method. To verify our code, we first perform a series of standard radiation tests with analytical solutions that include the check of gravitational redshift and Doppler shift. A good agreement in these tests supports the reliability of the GR multi-energy neutrino transport scheme. We then conduct several test simulations of core-collapse, bounce, and shock-stall of a 15Msun star in the Cartesian coordinates and make a detailed comparison with published results. Our code performs quite well to reproduce the results of full-Boltzmann neutrino transport especially before bounce. In the postbounce phase, our code basically performs well, however, there are several differences that are most likely to come from the insufficient spatial resolution in our current 3D-GR models. For clarifying the resolution dependence and extending the code comparison in the late postbounce phase, we discuss that next-generation Exaflops-class supercomputers are at least needed.