Improvements to the construction of binary black hole initial data

TL;DR

This paper presents enhancements to the binary black hole initial data solver in the Spectral Einstein Code, enabling more robust and efficient construction of initial data for high mass-ratios, high spins, and complex configurations.

Contribution

It introduces a flexible domain decomposition, adaptive mesh refinement, improved parameter selection, and a new method to control residual linear momentum in initial data.

Findings

Robust initial data construction for mass-ratio above 10:1

Effective elimination of gravitational mode mixing in precessing systems

Successful application to hyperbolic scattering and small separation binaries

Abstract

Construction of binary black hole initial data is a prerequisite for numerical evolutions of binary black holes. This paper reports improvements to the binary black hole initial data solver in the Spectral Einstein Code, to allow robust construction of initial data for mass-ratio above 10:1, and for dimensionless black hole spins above 0.9, while improving efficiency for lower mass-ratios and spins. We implement a more flexible domain decomposition, adaptive mesh refinement and an updated method for choosing free parameters. We also introduce a new method to control and eliminate residual linear momentum in initial data for precessing systems, and demonstrate that it eliminates gravitational mode mixing during the evolution. Finally, the new code is applied to construct initial data for hyperbolic scattering and for binaries with very small separation.