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Electromagnetic duality degeneracy in dynamical black hole mergers

José Ferreira1,*, Gabriele Bozzola2,†, Carlos A. R. Herdeiro1,‡, Vasileios Paschalidis3,4,§, and Miguel Zilhão5,∥

  • *Contact author: jpmferreira@ua.pt
  • †Contact author: gbozzola@amazon.com
  • ‡Contact author: herdeiro@ua.pt
  • §Contact author: vpaschal@arizona.edu
  • ∥Contact author: mzilhao@ua.pt
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Phys. Rev. D 114, 104024 – Published 6 November, 2026

DOI: https://doi.org/10.1103/9lfq-633s

Abstract

Electromagnetic duality is a symmetry of the source-free Einstein-Maxwell equations that rotates electric and magnetic fields while leaving the stress-energy tensor invariant. We present the first fully nonlinear realization of this symmetry in dynamical strong-gravity regimes by performing numerical relativity simulations of charged black hole mergers across a continuous duality family. Starting from electrically charged binaries, we generate dyonic and magnetically charged configurations via duality rotations and evolve them within a common numerical framework. We find that all dual configurations exhibit identical spacetime dynamics, while the emitted electromagnetic radiation is related by a rotation of its polarization equal to the duality angle. Our results demonstrate a degeneracy of gravitational observables under electromagnetic duality and provide a concrete mapping between dual configurations at the level of radiation, establishing electromagnetic duality as an organizing principle for dynamical Einstein-Maxwell solutions.

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Phys. Rev. D 114, 104024– Published 6 November, 2026
  • Received 30 June 2026
  • Accepted 1 October 2026
Article part of CHORUS
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