Reducing spurious gravitational radiation in binary-black-hole simulations by using conformally curved initial data

TL;DR

This paper demonstrates that using a conformally curved initial data approach with superposed boosted black holes significantly reduces spurious gravitational radiation in binary-black-hole simulations compared to traditional conformally flat methods.

Contribution

The paper introduces a conformally curved initial data method that decreases junk radiation in binary-black-hole simulations relative to standard conformally flat initial data.

Findings

SBS initial data reduces junk radiation amplitude compared to CFMS.

Spectral modes of junk radiation are decreased by a factor of two or more.

The approach improves the physical realism of early-time binary-black-hole simulations.

Abstract

At early times in numerical evolutions of binary black holes, current simulations contain an initial burst of spurious gravitational radiation (also called "junk radiation") which is not astrophysically realistic. The spurious radiation is a consequence of how the binary-black-hole initial data are constructed: the initial data are typically assumed to be conformally flat. In this paper, I adopt a curved conformal metric that is a superposition of two boosted, non-spinning black holes that are approximately 15 orbits from merger. I compare junk radiation of the superposed-boosted-Schwarzschild (SBS) initial data with the junk of corresponding conformally flat, maximally sliced (CFMS) initial data. The SBS junk is smaller in amplitude than the CFMS junk, with the junk's leading-order spectral modes typically being reduced by a factor of order two or more.