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Main Authors: Bah, Ibrahima, Berti, Emanuele, De Luca, Valerio, Ganchev, Bogdan, Pereñiguez, David
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2605.03018
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author Bah, Ibrahima
Berti, Emanuele
De Luca, Valerio
Ganchev, Bogdan
Pereñiguez, David
author_facet Bah, Ibrahima
Berti, Emanuele
De Luca, Valerio
Ganchev, Bogdan
Pereñiguez, David
contents Black hole perturbations are characterized by a superposition of damped exponentials known as quasinormal modes. In general relativity, the spectra of parity-even and parity-odd quasinormal modes coincide -- a property known as isospectrality, which is typically broken by corrections beyond general relativity. Recently, certain higher-derivative operators were shown to preserve isospectrality in the high-frequency (eikonal) regime. Motivated by the relation between the light ring Penrose limit and the eikonal limit, we study isospectrality in a class of plane-wave spacetimes. In general relativity, we show that dynamical metric fluctuations on these backgrounds admit a gravitational analog of electric-magnetic duality, which enforces isospectrality. Requiring this duality to persist in the presence of higher-derivative corrections constrains the couplings so that isospectrality is preserved. We conclude that gravitational electric-magnetic duality at the light ring is the organizing principle behind isospectrality in the eikonal limit, and we conjecture that this remains true for other duality-invariant corrections to general relativity.
format Preprint
id arxiv_https___arxiv_org_abs_2605_03018
institution arXiv
publishDate 2026
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spellingShingle Gravitational electric-magnetic duality at the light ring and quasinormal mode isospectrality in effective field theories
Bah, Ibrahima
Berti, Emanuele
De Luca, Valerio
Ganchev, Bogdan
Pereñiguez, David
General Relativity and Quantum Cosmology
High Energy Physics - Theory
Black hole perturbations are characterized by a superposition of damped exponentials known as quasinormal modes. In general relativity, the spectra of parity-even and parity-odd quasinormal modes coincide -- a property known as isospectrality, which is typically broken by corrections beyond general relativity. Recently, certain higher-derivative operators were shown to preserve isospectrality in the high-frequency (eikonal) regime. Motivated by the relation between the light ring Penrose limit and the eikonal limit, we study isospectrality in a class of plane-wave spacetimes. In general relativity, we show that dynamical metric fluctuations on these backgrounds admit a gravitational analog of electric-magnetic duality, which enforces isospectrality. Requiring this duality to persist in the presence of higher-derivative corrections constrains the couplings so that isospectrality is preserved. We conclude that gravitational electric-magnetic duality at the light ring is the organizing principle behind isospectrality in the eikonal limit, and we conjecture that this remains true for other duality-invariant corrections to general relativity.
title Gravitational electric-magnetic duality at the light ring and quasinormal mode isospectrality in effective field theories
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2605.03018