Quasinormal modes of rotating black holes beyond general relativity in the WKB approximation

Fuente: arXiv
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Auteurs principaux: Tang, Ruijing, Franchini, Nicola, Völkel, Sebastian H., Berti, Emanuele
Format: Preprint
Publié: 2025
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author Tang, Ruijing
Franchini, Nicola
Völkel, Sebastian H.
Berti, Emanuele
author_facet Tang, Ruijing
Franchini, Nicola
Völkel, Sebastian H.
Berti, Emanuele
contents Exploring gravitational theories beyond general relativity (GR) with black hole (BH) spectroscopy requires accurate and flexible methods for computing their quasinormal mode (QNM) spectrum. A popular method of choice is the higher-order Wentzel-Kramers-Brillouin (WKB) approximation, mostly applied to nonrotating BHs. While previous studies demonstrated that the higher-order WKB method can also be used for Kerr BHs in GR, there has been little work on rotating BHs in modified theories of gravity. In this work, we revive the idea by extending WKB calculations of the Kerr QNM spectrum to higher order and assessing its accuracy against continued-fraction tabulated data. We then apply the WKB approximation beyond GR, comparing it against both linearized and continued fraction calculations in the parametrized beyond-Teukolsky formalism and in higher-derivative gravity (HDG) theories. We find that the frequencies computed by the WKB method in theories beyond GR have better accuracy than the measurement errors for GW250114, the event with the highest ringdown signal-to-noise ratio observed to date.
format Preprint
id arxiv_https___arxiv_org_abs_2512_17786
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Quasinormal modes of rotating black holes beyond general relativity in the WKB approximation
Tang, Ruijing
Franchini, Nicola
Völkel, Sebastian H.
Berti, Emanuele
General Relativity and Quantum Cosmology
High Energy Physics - Theory
Exploring gravitational theories beyond general relativity (GR) with black hole (BH) spectroscopy requires accurate and flexible methods for computing their quasinormal mode (QNM) spectrum. A popular method of choice is the higher-order Wentzel-Kramers-Brillouin (WKB) approximation, mostly applied to nonrotating BHs. While previous studies demonstrated that the higher-order WKB method can also be used for Kerr BHs in GR, there has been little work on rotating BHs in modified theories of gravity. In this work, we revive the idea by extending WKB calculations of the Kerr QNM spectrum to higher order and assessing its accuracy against continued-fraction tabulated data. We then apply the WKB approximation beyond GR, comparing it against both linearized and continued fraction calculations in the parametrized beyond-Teukolsky formalism and in higher-derivative gravity (HDG) theories. We find that the frequencies computed by the WKB method in theories beyond GR have better accuracy than the measurement errors for GW250114, the event with the highest ringdown signal-to-noise ratio observed to date.
title Quasinormal modes of rotating black holes beyond general relativity in the WKB approximation
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2512.17786