The Sound of an Orbit: A Quantum Spectrum at the ISCO

Fuente: arXiv
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Autores principales: Pantig, Reggie C., Övgün, Ali
Formato: Preprint
Publicado: 2025
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author Pantig, Reggie C.
Övgün, Ali
author_facet Pantig, Reggie C.
Övgün, Ali
contents We investigate the quantum signature of the innermost stable circular orbit (ISCO), a region of profound importance in black hole astrophysics. By modeling an atom as an Unruh-DeWitt detector coupled to a massless scalar field in the Boulware vacuum, we calculate the excitation rate for a detector following a circular geodesic at the ISCO of a Schwarzschild black hole. In stark contrast to the continuous thermal spectra associated with static or infalling observers, our analysis reveals a unique, non-thermal excitation spectrum characterized by a discrete "frequency comb" of sharp, resonant peaks. We show that the locations of these peaks are determined by the orbital frequency at the ISCO, while their intensity increases dramatically as the orbit approaches this final stability boundary. This distinct spectral signature offers a novel theoretical probe of the quantum vacuum in a strong-field gravitational regime and provides a clear distinction between the quantum phenomena experienced by observers on different trajectories. Our findings have potential implications for interpreting the emission spectra from accretion disks and open new avenues for exploring the connection between quantum mechanics and gravity.
format Preprint
id arxiv_https___arxiv_org_abs_2507_14254
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Sound of an Orbit: A Quantum Spectrum at the ISCO
Pantig, Reggie C.
Övgün, Ali
General Relativity and Quantum Cosmology
High Energy Physics - Theory
Quantum Physics
We investigate the quantum signature of the innermost stable circular orbit (ISCO), a region of profound importance in black hole astrophysics. By modeling an atom as an Unruh-DeWitt detector coupled to a massless scalar field in the Boulware vacuum, we calculate the excitation rate for a detector following a circular geodesic at the ISCO of a Schwarzschild black hole. In stark contrast to the continuous thermal spectra associated with static or infalling observers, our analysis reveals a unique, non-thermal excitation spectrum characterized by a discrete "frequency comb" of sharp, resonant peaks. We show that the locations of these peaks are determined by the orbital frequency at the ISCO, while their intensity increases dramatically as the orbit approaches this final stability boundary. This distinct spectral signature offers a novel theoretical probe of the quantum vacuum in a strong-field gravitational regime and provides a clear distinction between the quantum phenomena experienced by observers on different trajectories. Our findings have potential implications for interpreting the emission spectra from accretion disks and open new avenues for exploring the connection between quantum mechanics and gravity.
title The Sound of an Orbit: A Quantum Spectrum at the ISCO
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
Quantum Physics
url https://arxiv.org/abs/2507.14254