When the Ringing Stops: Purely Imaginary Modes in the Ringdown Spectrum of Dynamical Black Holes

Fuente: arXiv
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Hauptverfasser: Capuano, Lodovico, Lovo, Thomas, Prieto-Varela, Gorka, Sarkar, Subhodeep, Kuntz, Adrien, Barausse, Enrico, Kothawala, Dawood
Format: Preprint
Veröffentlicht: 2026
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author Capuano, Lodovico
Lovo, Thomas
Prieto-Varela, Gorka
Sarkar, Subhodeep
Kuntz, Adrien
Barausse, Enrico
Kothawala, Dawood
author_facet Capuano, Lodovico
Lovo, Thomas
Prieto-Varela, Gorka
Sarkar, Subhodeep
Kuntz, Adrien
Barausse, Enrico
Kothawala, Dawood
contents We extend the frequency-domain analysis of quasinormal modes in a dynamical, spherically symmetric black hole spacetime undergoing constant-rate mass evolution. In particular, we report a novel feature of the spectrum: the presence of purely imaginary eigenvalues in addition to the usual light-ring modes. We study the frequencies of these modes both analytically and numerically. The analytical calculation uses a novel formalism based on recent advances in connection coefficients of Heun functions. We then compute the frequencies numerically using a spectral method on hyperboloidal slices and find excellent agreement between the two approaches. Finally, we validate the frequency-domain results against an independent set of time-domain simulations. Our analysis shows that the purely imaginary modes govern the late-time signal through exponentially decaying tails. In the Schwarzschild limit, both frequency- and time-domain studies consistently show that the purely imaginary modes give rise to the familiar Schwarzschild power-law tail.
format Preprint
id arxiv_https___arxiv_org_abs_2605_28951
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle When the Ringing Stops: Purely Imaginary Modes in the Ringdown Spectrum of Dynamical Black Holes
Capuano, Lodovico
Lovo, Thomas
Prieto-Varela, Gorka
Sarkar, Subhodeep
Kuntz, Adrien
Barausse, Enrico
Kothawala, Dawood
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
High Energy Physics - Theory
We extend the frequency-domain analysis of quasinormal modes in a dynamical, spherically symmetric black hole spacetime undergoing constant-rate mass evolution. In particular, we report a novel feature of the spectrum: the presence of purely imaginary eigenvalues in addition to the usual light-ring modes. We study the frequencies of these modes both analytically and numerically. The analytical calculation uses a novel formalism based on recent advances in connection coefficients of Heun functions. We then compute the frequencies numerically using a spectral method on hyperboloidal slices and find excellent agreement between the two approaches. Finally, we validate the frequency-domain results against an independent set of time-domain simulations. Our analysis shows that the purely imaginary modes govern the late-time signal through exponentially decaying tails. In the Schwarzschild limit, both frequency- and time-domain studies consistently show that the purely imaginary modes give rise to the familiar Schwarzschild power-law tail.
title When the Ringing Stops: Purely Imaginary Modes in the Ringdown Spectrum of Dynamical Black Holes
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
High Energy Physics - Theory
url https://arxiv.org/abs/2605.28951