Initial data transients in binary black hole evolutions

TL;DR

This paper introduces a method for initializing characteristic evolutions in Einstein's equations using linearized outgoing radiation solutions, improving the analysis of gravitational waves in black hole simulations.

Contribution

It presents a new initialization technique for characteristic evolutions that identifies ingoing and outgoing radiation, reducing transients in gravitational wave measurements.

Findings

Transient effects last for several hundred mass scales.

The method improves the consistency of gravitational radiation extraction.

Ingoing radiation components are successfully identified.

Abstract

We describe a method for initializing characteristic evolutions of the Einstein equations using a linearized solution corresponding to purely outgoing radiation. This allows for a more consistent application of the characteristic (null cone) techniques for invariantly determining the gravitational radiation content of numerical simulations. In addition, we are able to identify the {\em ingoing} radiation contained in the characteristic initial data, as well as in the initial data of the 3+1 simulation. We find that each component leads to a small but long lasting (several hundred mass scales) transient in the measured outgoing gravitational waves.