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Cited by 303Quantum and Classical ElectrodynamicsRelativity and Gravitational TheoryParticle physics theoretical and experimental studies

The mass of the photon

Tu, Liang-Cheng, Luo, Jun, Gillies, George T·2005·Reports on Progress in Physics
DOI 10.1088/0034-4885/68/1/r02
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Abstract

Because classical Maxwellian electromagnetism has been one of the cornerstones of physics during the past century, experimental tests of its foundations are always of considerable interest. Within that context, one of the most important efforts of this type has historically been the search for a rest mass of the photon. The effects of a nonzero photon rest mass can be incorporated into electromagnetism straightforwardly through the Proca equations, which are the simplest relativistic generalization of Maxwell's equations. Using them, it is possible to consider some far-reaching implications of a massive photon, such as variation of the speed of light, deviations in the behaviour of static electromagnetic fields, longitudinal electromagnetic radiation and even questions of gravitational deflection. All of these have been studied carefully using a number of different approaches over the past several decades. This review attempts to assess the status of our current knowledge and understanding of the photon rest mass, with particular emphasis on a discussion of the various experimental methods that have been used to set upper limits on it. All such tests can be most easily categorized in terms of terrestrial and extra-terrestrial approaches, and the review classifies them as such. Up to now, there has been no conclusive evidence of a finite mass for the photon, with the results instead yielding ever more stringent upper bounds on the size of it, thus confirming the related aspects of Maxwellian electromagnetism with concomitant precision. Of course, failure to find a finite photon mass in any one experiment or class of experiments is not proof that it is identically zero and, even as the experimental limits move more closely towards the fundamental bounds of measurement uncertainty, new conceptual approaches to the task continue to appear. The intrinsic importance of the question and the lure of what might be revealed by attaining the next decimal place are as strong a draw on this question as they are in any other aspect of precise tests of physical laws.

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Crossref · 10.1088/0034-4885/68/1/r02

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204 of 204 references verified0 citation errors · 0 not checkable

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  • When ξ is positive, equation (10) is equivalent to the Proca equation.

    “When ξ is positive, this equation is equivalent to the Proca equation [34-36] and m A ≡ ξ 1 / 2 can be interpreted as the rest mass of photons.”

    From Electrodynamics on cosmological scales (2016) · cites this paper as [35]

  • m_A ≡ ξ^{1/2} can be interpreted as the rest mass of photons.

    “When ξ is positive, this equation is equivalent to the Proca equation [34-36] and m A ≡ ξ 1 / 2 can be interpreted as the rest mass of photons.”

    From Electrodynamics on cosmological scales (2016) · cites this paper as [35]

  • If longitudinal photons interact with matter sufficiently weakly or do not interact with matter at all, we still get g = 2 and the Stephan-Boltzmann law remains valid.

    “If they interact with matter sufficiently weak or do not interact with matter at all, we still get g = 2 and the Stephan-Boltzmann law remains valid [35, 36, 58].”

    From Electrodynamics on cosmological scales (2016) · cites this paper as [35]

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Authors
Tu, L.-C., Luo, J., & Gillies, G. T.
Affiliations
  • Huazhong University of Science and Technology (CN)
  • University of Virginia (US)
Corresponding author
Gillies, George T
ORCID
Venue
Reports on Progress in Physics
Publisher
IOP Publishing
Published
2004-11-24
Volume
68
Issue
1
Pages
77-130
ISSN
  • 0034-4885 (ISSN-L)
  • 1361-6633
DOI
10.1088/0034-4885/68/1/r02
OpenAlex
W2153158728
Cited by
303
References
205
Citations by year
2026: 13 · 2025: 17 · 2024: 23 · 2023: 32 · 2022: 14 · 2021: 12 · 2020: 9 · 2019: 10 · 2018: 13 · 2017: 10 · 2016: 28 · 2015: 17 · 2014: 17 · 2013: 19 · 2012: 9
FWCI
4.50
Type
journal article
Language
en
Open access
closed
Locations
Reports on Progress in Physics (publishedVersion)
Topics
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum and Classical Electrodynamics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Relativity and Gravitational Theory
  • Physical Sciences › Physics and Astronomy › Nuclear and High Energy Physics › Particle physics theoretical and experimental studies
Keywords
photon mass, Proca equation, modified Maxwell equations, variable speed of light, gravitational deflection

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