Binary neutron-star mergers with Whisky and SACRA: First quantitative comparison of results from independent general-relativistic hydrodynamics codes

TL;DR

This paper compares two independent general-relativistic hydrodynamics codes, Whisky and SACRA, in simulating binary neutron-star mergers, demonstrating their results agree within 10% for key physical quantities and gravitational waveforms.

Contribution

It provides the first quantitative comparison of two independent codes for neutron-star merger simulations, validating their consistency and accuracy.

Findings

Results agree within 10% for conserved quantities.

Gravitational waveforms are consistent between codes.

The comparison establishes reliability of simulation methods.

Abstract

We present the first quantitative comparison of two independent general-relativistic hydrodynamics codes, the Whisky code and the SACRA code. We compare the output of simulations starting from the same initial data and carried out with the configuration (numerical methods, grid setup, resolution, gauges) which for each code has been found to give consistent and sufficiently accurate results, in particular in terms of cleanness of gravitational waveforms. We focus on the quantities that should be conserved during the evolution (rest mass, total mass energy, and total angular momentum) and on the gravitational-wave amplitude and frequency. We find that the results produced by the two codes agree at a reasonable level, with variations in the different quantities but always at better than about 10%.