Gravitational Waves on Kerr Black Holes I: Reconstruction of Linearized Metric Perturbations

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Auteurs principaux: Berens, Roman, Gravely, Trevor, Lupsasca, Alexandru
Format: Preprint
Publié: 2024
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author Berens, Roman
Gravely, Trevor
Lupsasca, Alexandru
author_facet Berens, Roman
Gravely, Trevor
Lupsasca, Alexandru
contents The gravitational perturbations of a rotating Kerr black hole are notoriously complicated, even at the linear level. In 1973, Teukolsky showed that their physical degrees of freedom are encoded in two gauge-invariant Weyl curvature scalars that obey a separable wave equation. Determining these scalars is sufficient for many purposes, such as the computation of energy fluxes. However, some applications -- such as second-order perturbation theory -- require the reconstruction of metric perturbations. In principle, this problem was solved long ago, but in practice, the solution has never been worked out explicitly. Here, we do so by writing down the metric perturbation (in either ingoing or outgoing radiation gauge) that corresponds to a given mode of either Weyl scalar. Our formulas make no reference to the Hertz potential (an intermediate quantity that plays no fundamental role) and involve only the radial and angular Kerr modes, but not their derivatives, which can be altogether eliminated using the Teukolsky--Starobinsky identities. We expect these analytic results to prove useful in numerical studies and for extending black hole perturbation theory beyond the linear regime.
format Preprint
id arxiv_https___arxiv_org_abs_2403_20311
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Gravitational Waves on Kerr Black Holes I: Reconstruction of Linearized Metric Perturbations
Berens, Roman
Gravely, Trevor
Lupsasca, Alexandru
General Relativity and Quantum Cosmology
High Energy Physics - Theory
The gravitational perturbations of a rotating Kerr black hole are notoriously complicated, even at the linear level. In 1973, Teukolsky showed that their physical degrees of freedom are encoded in two gauge-invariant Weyl curvature scalars that obey a separable wave equation. Determining these scalars is sufficient for many purposes, such as the computation of energy fluxes. However, some applications -- such as second-order perturbation theory -- require the reconstruction of metric perturbations. In principle, this problem was solved long ago, but in practice, the solution has never been worked out explicitly. Here, we do so by writing down the metric perturbation (in either ingoing or outgoing radiation gauge) that corresponds to a given mode of either Weyl scalar. Our formulas make no reference to the Hertz potential (an intermediate quantity that plays no fundamental role) and involve only the radial and angular Kerr modes, but not their derivatives, which can be altogether eliminated using the Teukolsky--Starobinsky identities. We expect these analytic results to prove useful in numerical studies and for extending black hole perturbation theory beyond the linear regime.
title Gravitational Waves on Kerr Black Holes I: Reconstruction of Linearized Metric Perturbations
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2403.20311