Black Hole Photon Rings Saturate the Quantum Chaos Bound

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Main Authors: Giataganas, D., Giudice, G. F., Kehagias, A., Quevedo, F., Riotto, A.
Format: Preprint
Published: 2026
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author Giataganas, D.
Giudice, G. F.
Kehagias, A.
Quevedo, F.
Riotto, A.
author_facet Giataganas, D.
Giudice, G. F.
Kehagias, A.
Quevedo, F.
Riotto, A.
contents We study the quantum chaos bound in the photon ring region surrounding black holes. By evaluating the Lyapunov exponent associated with unstable null geodesics in a broad class of generalized Kerr geometries, as well as the temperature induced by a string probe, we show that the quantum chaos bound is exactly saturated on equatorial circular orbits of the photon ring. We confirm our result by deriving the same exponent from out-of-time-order correlators in the near ring region. As a byproduct, we show that the photon ring saturation of the quantum chaos bound implies the saturation of the Bekenstein bound on the rate of information emission from the ringdown phase through the quasi-normal modes in the eikonal limit. Our results extend the known correspondence between black hole thermodynamics and chaotic dynamics, highlighting the role of the photon ring as a probe of the fundamental limits on thermalization and information scrambling in black holes.
format Preprint
id arxiv_https___arxiv_org_abs_2605_29923
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Black Hole Photon Rings Saturate the Quantum Chaos Bound
Giataganas, D.
Giudice, G. F.
Kehagias, A.
Quevedo, F.
Riotto, A.
High Energy Physics - Theory
Cosmology and Nongalactic Astrophysics
General Relativity and Quantum Cosmology
High Energy Physics - Phenomenology
We study the quantum chaos bound in the photon ring region surrounding black holes. By evaluating the Lyapunov exponent associated with unstable null geodesics in a broad class of generalized Kerr geometries, as well as the temperature induced by a string probe, we show that the quantum chaos bound is exactly saturated on equatorial circular orbits of the photon ring. We confirm our result by deriving the same exponent from out-of-time-order correlators in the near ring region. As a byproduct, we show that the photon ring saturation of the quantum chaos bound implies the saturation of the Bekenstein bound on the rate of information emission from the ringdown phase through the quasi-normal modes in the eikonal limit. Our results extend the known correspondence between black hole thermodynamics and chaotic dynamics, highlighting the role of the photon ring as a probe of the fundamental limits on thermalization and information scrambling in black holes.
title Black Hole Photon Rings Saturate the Quantum Chaos Bound
topic High Energy Physics - Theory
Cosmology and Nongalactic Astrophysics
General Relativity and Quantum Cosmology
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2605.29923