Larmor radiation as a witness to the Unruh effect

Atsushi Higuchi; George E. A. Matsas; Daniel A. T. Vanzella; Robert Bingham; João P. B. Brito; Luís C. B. Crispino; Gianluca Gregori; Georgios Vacalis

doi:10.1103/494h-9r4d

Larmor radiation as a witness to the Unruh effect

Atsushi Higuchi^*, George E. A. Matsas, Daniel A. T. Vanzella, Robert Bingham, João P. B. Brito, Luís C. B. Crispino, Gianluca Gregori, Georgios Vacalis

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

We discuss the emission of radiation from general sources in quantum scalar, electromagnetic, and gravitational fields using the Rindler coordinate frame, which is suitable for uniformly accelerated observers, in the Minkowski vacuum. In particular, we point out that to recover, from the point of view of uniformly accelerated observers in the interaction picture, the usual Larmor radiation, which is independent of the choice of the vacuum state, it is necessary to incorporate the Unruh effect assuming the Minkowski vacuum. Thus, the observation of classical Larmor radiation in the Minkowski vacuum could be seen as vindicating the Unruh effect in the sense that it is not correctly recovered in the uniformly accelerated frame unless the Unruh effect is taken into account.

Original language	English
Article number	065009
Number of pages	12
Journal	Physical Review D
Volume	112
Issue number	6
DOIs	https://doi.org/10.1103/494h-9r4d
Publication status	Published - 16 Sept 2025

Funding

We are thankful to F. Portales-Oliva for calling our attention to Ref. [13]. D. V. would like to thank the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Science for hosting him during a sabbatical year. G. M. and D. V. were supported in part by São Paulo Research Foundation (FAPESP) under grants 2021/09293-7 and 2023/04827-9, respectively. G. M. was also partially supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under grant 302674/2018-7. The work of J. B. and L. C. was supported in part by Fundação Amazônia de Amparo a Estudos e Pesquisas (FAPESPA), CNPq and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)—Finance Code 001. Their work has also been supported by the European Horizon Europe staff exchange (SE) programme HORIZONMSCA-2021-SE-01 Grant No. NewFunFiCO-101086251. The work of R. B. and G. G. was supported in part by EPSRC grants No. EP/ X01133X/1 and No. EP/X010791/1. G. G. is also a member of the Quantum Sensing for the Hidden Sector (QSHS) collaboration, supported by STFC Grant No. ST/T006277/1.

Keywords

Quantum field theory
Quantum fields in curved spacetime

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title = "Larmor radiation as a witness to the Unruh effect",

abstract = "We discuss the emission of radiation from general sources in quantum scalar, electromagnetic, and gravitational fields using the Rindler coordinate frame, which is suitable for uniformly accelerated observers, in the Minkowski vacuum. In particular, we point out that to recover, from the point of view of uniformly accelerated observers in the interaction picture, the usual Larmor radiation, which is independent of the choice of the vacuum state, it is necessary to incorporate the Unruh effect assuming the Minkowski vacuum. Thus, the observation of classical Larmor radiation in the Minkowski vacuum could be seen as vindicating the Unruh effect in the sense that it is not correctly recovered in the uniformly accelerated frame unless the Unruh effect is taken into account.",

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AU - Higuchi, Atsushi

AU - Matsas, George E. A.

AU - Vanzella, Daniel A. T.

AU - Bingham, Robert

AU - Brito, João P. B.

AU - Crispino, Luís C. B.

AU - Gregori, Gianluca

AU - Vacalis, Georgios

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N2 - We discuss the emission of radiation from general sources in quantum scalar, electromagnetic, and gravitational fields using the Rindler coordinate frame, which is suitable for uniformly accelerated observers, in the Minkowski vacuum. In particular, we point out that to recover, from the point of view of uniformly accelerated observers in the interaction picture, the usual Larmor radiation, which is independent of the choice of the vacuum state, it is necessary to incorporate the Unruh effect assuming the Minkowski vacuum. Thus, the observation of classical Larmor radiation in the Minkowski vacuum could be seen as vindicating the Unruh effect in the sense that it is not correctly recovered in the uniformly accelerated frame unless the Unruh effect is taken into account.

AB - We discuss the emission of radiation from general sources in quantum scalar, electromagnetic, and gravitational fields using the Rindler coordinate frame, which is suitable for uniformly accelerated observers, in the Minkowski vacuum. In particular, we point out that to recover, from the point of view of uniformly accelerated observers in the interaction picture, the usual Larmor radiation, which is independent of the choice of the vacuum state, it is necessary to incorporate the Unruh effect assuming the Minkowski vacuum. Thus, the observation of classical Larmor radiation in the Minkowski vacuum could be seen as vindicating the Unruh effect in the sense that it is not correctly recovered in the uniformly accelerated frame unless the Unruh effect is taken into account.

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KW - Quantum fields in curved spacetime

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JO - Physical Review D

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Larmor radiation as a witness to the Unruh effect

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