The gravitational wave strain in the characteristic formalism of numerical relativity

TL;DR

This paper develops and tests a new formula for extracting gravitational wave strain in characteristic numerical relativity, reducing non-linear drifts in some cases and highlighting challenges in others.

Contribution

It introduces a new strain formula implemented in the PITT code, improving waveform extraction in numerical relativity simulations.

Findings

Reduced non-linear drifts in binary black hole merger waveforms

Demonstrated limitations of the new formula in stellar core collapse cases

Provided publicly available code for the scientific community

Abstract

The extraction of the gravitational wave signal, within the context of a characteristic numerical evolution is revisited. A formula for the gravitational wave strain is developed and tested, and is made publicly available as part of the PITT code within the Einstein Toolkit. Using the new strain formula, we show that artificial non-linear drifts inherent in time integrated waveforms can be reduced for the case of a binary black hole merger configuration. For the test case of a rapidly spinning stellar core collapse model, however, we find that the drift must have different roots.