Non-minimal light-curvature couplings and black-hole imaging

2025/05/27 by Raúl Carballo-Rubio, Carballo-Rubio, Raúl, Héloïse Delaporte +5 · 2 citations
Medicine · #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Phenomenology (hep-ph) #Medical Imaging Techniques and Applications

paper · pdf · doi:10.48550/arxiv.2505.21431

openalex publication_date 2025/05/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01

Abstract

Non-minimal couplings between the electromagnetic field strength and the spacetime curvature are part of the effective field theory of gravity and matter. They alter the local propagation of light in a significant way if the ratio of spacetime curvature to the non-minimal coupling is of order one. Spacetime curvature can become appreciable around black holes, and yet the effect of non-minimal couplings on electromagnetic observations of black holes remains underexplored. A particular feature of the non-minimal coupling between the electromagnetic field-strength and the Riemann tensor is that it generates two distinct photon rings for different polarizations. Working within the paradigm of lensing bands and focusing on the n = 1 lensing band, we illustrate by which diagnostics a modified light propagation may be distinguished from a modified spacetime geometry and how constraints on the value of the non-minimal coupling can be obtained

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