The DOI matches its Crossref record; 204 of the 205 references it cites were found in a registry or an index.
The mass of the photon
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.
Overview
Integrity signals
Registry
Cites
Statistics
Verification
Claims the paper makes
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
In the citing paper
“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]
In the citing paper
“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]
In the citing paper
“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]
Citations
Cites
(2020) · Princeton University Press eBooks · doi:10.2307/j.ctv131bv37.5 · Cited by 22,595
A treatise on electricity and magnetism
(1954) · Journal of the Franklin Institute · doi:10.1016/0016-0032(54)90053-8 · Cited by 9,134
Significance of Electromagnetic Potentials in the Quantum Theory
Aharonov, Y., & Bohm, D. (1959) · Physical Review · doi:10.1103/physrev.115.485 · Cited by 6,996
The hierarchy problem and new dimensions at a millimeter
Arkani–Hamed, N., Dimopoulos, S., & Dvali, G. (1998) · Physics Letters B · doi:10.1016/s0370-2693(98)00466-3 · Cited by 6,563
Particle Data Group, Workman, R., Burkert, V., Credé, V., Klempt, E., Thoma, U., Tiator, L., Agashe, K., Aielli, G., Allanach, B. C., et al. (2022) · Progress of Theoretical and Experimental Physics · doi:10.1093/ptep/ptac097 · Cited by 6,080
A Treatise on Electricity and Magnetism
(1873) · Nature · doi:10.1038/007478a0 · Cited by 4,538
Yost, G. P., Barnett, R. M., Hinchliffe, I., Lynch, G., Rittenberg, A., Ross, R. R., Suzuki, M., TRIPPE, T. G., Wohl, C. G., Armstrong, B., et al. (1988) · Physics Letters B · doi:10.1016/0370-2693(88)90505-9 · Cited by 4,401
The work function of the elements and its periodicity
Michaelson, H. B. (1977) · Journal of Applied Physics · doi:10.1063/1.323539 · Cited by 4,304
Quantised singularities in the electromagnetic field,
Dirac, P. A. M. (1931) · Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character · doi:10.1098/rspa.1931.0130 · Cited by 3,701
Hagiwara, K., Hikasa, K., Nakamura, K., Tanabashi, M., Aguilar-Benitez, M., Amsler, C., Barnett, R. M., Burchat, P. R., Carone, C. D., Caso, C., et al. (2002) · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · doi:10.1103/physrevd.66.010001 · Cited by 3,354
Research works printed but not linked: 26
- Al'pert Y L, 1941, Zh. Tech. Fiz., 11, 7
- Alfvén H, 1968, Ann. Geophys., 24, 341
- Bartlett D F, 1969, Bull. Am. Phys. Soc., 14, 17
- Binney J, 1987, Galactic Dynamics, 211
- Casimir H B G, 1948, Proc. K. Ned. Akad. Wet., 51, 793
- Clear J, 1987, Astron. Astrophys., 174, 85
- Cochran G D, 1968, Bull. Am. Phys. Soc., 13, 1379
- Elliott R S, 1966, Electromagnetics
- Gintsburg M A, 1963, Astron. Zh., 40, 703
- Gintsburg M A, 1964, Sov. Astron.-AJ, 7, 536
- Lehnert B, 2000, J. New Energy, 5, 81
- Norman T, 1987, The Atomic Constants Light and Time
- Proca A, 1930, Compt. Rend., 190, 1377
- Proca A, 1930, Compt. Rend., 191, 26
- Proca A, 1931, Compt. Rend., 193, 832
- Proca A, 1936, Compt. Rend., 202, 1366
- Proca A, 1936, Compt. Rend., 202, 1490
- Proca A, 1936, Compt. Rend., 203, 709
- Proca A, 1938, J. Physique Ser. VII, 9, 61
- Schrödinger E, 1943, Proc. R. Ir. Acad., 49, 135
- Schrödinger E, 1943, Proc. R. Ir. Acad., 49, 43
- Stueckelberg E C G, 1941, Helv. Phys. Acta, 14, 51
- Stueckelberg E C G, 1957, Helv. Phys. Acta, 30, 209
- Wilkie T, 1983, New Sci., 100, 258
- Williams E R, 1970, Bull. Am. Phys. Soc., 15, 586
- Zhang Y Z, 1998, Speical Relativity and its Experimental Foundations, 245
Cited by
Sorted by citations
Items 201–300 of 302
Linking photons and ultra-light particles
Ben‐Amotz, D. (2018) · Chemical Physics · doi:10.1016/j.chemphys.2018.03.032 · Cited by 1
Analytical solution of the proca equation for the modified posch teller potential
Suparmi, S., Pamungkas, O. R., & Cari, C. (2019) · Journal of Physics Conference Series · doi:10.1088/1742-6596/1153/1/012102 · Cited by 1
A massive gauge theory à la Utiyama
Cuzinatto, R. R., Pimentel, B. M., Pompeia, P. J., & Esquia, J. C. S. (2023) · Physica Scripta · doi:10.1088/1402-4896/ace561 · Cited by 1
Aharonov-Bohm effect in Generalized Electrodynamics
de Melo, C. A. M., Peres, B., Esquia, J. C. S., & Cuzinatto, R. R. (2024) · Nuclear Physics B · doi:10.1016/j.nuclphysb.2024.116616 · Cited by 1
“The latter should be submicroscopic in order to Podolsky’s corrections to Maxwell theory be small, as required by extensive tests of the standard electrodynamics [41, 42].”
BackgroundReference frame dependence of the periodically oscillating Coulomb field in the Proca theory
Damski, B. (2024) · Nuclear Physics B · doi:10.1016/j.nuclphysb.2024.116636 · Cited by 1
A connection between massive electrodynamics and the Einstein-Maxwell equations
Alqrayan, W. A., & Arbab, A. I. (2024) · Physica Scripta · doi:10.1088/1402-4896/ad8283 · Cited by 1
Bounds on the photon mass via the Shapiro effect in the solar system
Malta, P. C., & Zarro, C. A. D. (2024) · Physical review. D/Physical review. D. · doi:10.1103/physrevd.110.095017 · Cited by 2
“The most stringent upper bound currently accepted is m γ ≤ 10 − 18 eV / c 2 ≈ 10 − 51 g extracted from data from the Voyager missions [4]; for reviews, see the latest edition of the Particle Data Group [5], as well as refs.”
Radiation and Scattering of Massive Photons
Saiyan, G. A. (2024) · Communications of the Byurakan Astrophysical Observatory · doi:10.52526/25792776-24.71.2-307 · Cited by 1
Perturbative solutions for compact objects in (2+1)-dimensional Bopp–Podolsky electrodynamics
Maluf, R. V., Silva, J. E. G., Almeida, C. A. S., & Olmo, G. J. (2025) · The European Physical Journal C · doi:10.1140/epjc/s10052-025-14314-7 · Cited by 1
Electromagnetic momentum in frontiers of modern physics
Spavieri, G., Erazo, J., Pineda, A. R. S., Aguirre, F., Gillies, G. T., & Rodriguez, M. (2008) · 物理学前沿：英文版 · doi:10.1007/s11467-008-0036-9 · Cited by 1
Self-citationLi, C.-D., & Cheng, Y.-F. (2007) · International Journal of Theoretical Physics · doi:10.1007/s10773-007-9635-4 · Cited by 1
A Vanishingly Small Vector Mass from Anisotropy of Higher Dimensional Spacetime
Kim, T.-G., & Oh, P. (2020) · Journal of the Korean Physical Society · doi:10.3938/jkps.77.463 · Cited by 1
Atomic Spectroscopy and the Photon Mass: Effects on the hydrogen ground-state
Rodriguez, M., & Pirela, M. C. P. (2020) · International Journal of Engineering Research and Technology · doi:10.37624/ijert/13.8.2020.2096-2099 · Cited by 1
Phenomenological implications of a magnetic 5th force
Krause, D. E., Bertaux, J., McNamara, A. M., Gruenwald, J. T., Longman, A., Scarlett, C., & Fischbach, E. (2023) · International Journal of Modern Physics A · doi:10.1142/s0217751x23500070 · Cited by 1
Caswell, J. M. (2014) · Lu Zone Ul (Laurentian University) · Cited by 1
Электродинамика связанного фотонного состояния в четырёхмерном пространствеPreprint
Kazakov, V. (2026) · doi:10.24108/preprints-3116495 · Cited by 1
The Scalar-photon Coupling with Mie Invariant Within the Scope of Bianchi Type-I Cosmological Model
Muharlyamov, R. K., & Pankratyeva, T. N. (2015) · International Journal of Theoretical Physics · doi:10.1007/s10773-015-2752-6
The consequences of complex Lorentz force and violation of Lorenz gauge conditionPreprint
Arbab, A. I. (2013) · arXiv (Cornell University) · doi:10.48550/arxiv.1302.0695
“For a comprehensive limit on the photon mass we suggest that the reader should refer to reference [21].”
BackgroundOptics and Spectroscopy in Massive Electrodynamic Theory
Caccavano, A. (2000) · doi:10.15760/etd.1484
“This chapter summarizes previous theoretical accomplishments, beginning with Proca’s formalism [1] [2] [3] [4] [5] and further investigating static fields [6], dynamic fields, and plane wave solutions [7], [8].”
BackgroundMethodThe Rest Mass of a PhotonPreprint
Rajpal, K. L. (2013) · viXra
Momento electromagnético, efectos cuánticos y la masa del fotón
Spavieri, G., Erazo, J., Sánchez, A., & Rodriguez, M. (2009) · Redalyc (Universidad Autónoma del Estado de México)
One hundred years of the photon
Milant’ev, V. P. (2005) · Physics-Uspekhi · doi:10.1070/pu2005v048n11abeh005819
Influence of Photon Mass on Vacuum Birefringence Experiment
Min, C., & Shao, C.-G. (2007) · Chinese Physics Letters · doi:10.1088/0256-307x/24/4/015
Nuevos efectos cuanticos del tipo Aharonov-Bohm y la masa del foton
Quintero, J. M., & Spavieri, G. (2011) · Publicaciones en Ciencias y Tecnología
The central tendency relationships between earthquakes, quantum fluctuations, and the human brain
Vares, D. A. E. (2014) · Lu Zone Ul (Laurentian University)
Nuclear Magneton Theory of Mass Quantization "Unified Field Theory"
Muhyedeen, B. R. J. (2013)
Magnetic field and EoS of neutron star matter at finite temperature
Wang, Q.-W., & Lü, X.-F. (2015) · International Journal of Modern Physics E · doi:10.1142/s0218301315500512
Liu, L.-X., & Deng, G. (2012) · Communications in Theoretical Physics · doi:10.1088/0253-6102/58/3/16
E = Mc2 is Not Valid: New Sources of Energy from LightPreprint
Nwogugu, M. C. I. (2006) · SSRN Electronic Journal · doi:10.2139/ssrn.910921
Christianto, V. (2016) · viXra
Persinger, M. A. (2016) · JOURNAL OF ADVANCES IN PHYSICS · doi:10.24297/jap.v11i8.195
Exploration Minkowski Space & Consciousness
Carniello, T. N. (2013)
The New Process of the Study on Light Velocity and Photon Mass
阚, 学. (2016) · Modern Physics · doi:10.12677/mp.2016.65015
Lehman, B. S. (2016) · Lu Zone Ul (Laurentian University) · doi:10.13140/rg.2.1.2010.8402
Chapter 2 Introduction to Photonics
(2016) · CRC Press eBooks · doi:10.1201/9781315373072-3
Carniello, T. N. (2016) · Lu Zone Ul (Laurentian University)
The New Process of the Study on Light Velocity and Photon Mass
Xue-min, K. (2016)
special theory of relativity for photonsPreprint
Albanay, Y. (2013) · HAL
Persinger, M. A. (2016) · World Scientific News
Light and Its Application to Relativity
Vanderwerf, D. F. (2017) · Springer eBooks · doi:10.1007/978-3-319-64316-8_3
Analytical solution of the Proca equation for a scalar potential
Pamungkas, O. R., Suparmi, S., & Cari, C. (2018) · AIP conference proceedings · doi:10.1063/1.5054551
Some Studies on Photon - A Review
Misra, R. (2018) · Zenodo (CERN European Organization for Nuclear Research) · doi:10.5281/zenodo.21565541
Are Photons Massless or Massive?
Nyambuya, G. G. (2019) · doi:10.13140/rg.2.2.26653.67047
Discussion on Mass in a Gravitational Field
Likui, Z. (2011)
Fuzzy operators and the quantized electromagnetic field in the very-high-energy regimePreprint
Parisio, F. (2019) · arXiv (Cornell University) · doi:10.48550/arxiv.1905.08206
“Although this possibility may be potentially interesting [16–19], for simplicity, we will not follow in this direction in the present work.”
BackgroundSuperconducting Detectors and Massive Gauge Bosons in Superconductivity
Brandt, D. (2009) · Leicester Research Archive (University of Leicester)
Christianto, V., Smarandache, F., & Umniyati, Y. (2020) · Journal of Condensed Matter Nuclear Science · doi:10.70923/001c.72541
“From Table 1 and also from other results as reported in [12], it seems that we can expect that someday photon mass can be observed within experimental bounds.”
Proca Metamaterials, Massive Electromagnetism, and NonlocalityPreprint
Mikki, S. M. (2021) · doi:10.36227/techrxiv.13567529.v1
“In the vector form, Maxwell-Proca equations are [10]:”
BackgroundMethodInfluentialQuantitative Convergence of Concepts in Physical Cosmology and Theology
Persinger, M. A., Burke, R. C., & Carniello, T. N. (2012) · Journal of Cosmology
Variation of Energy Density and Mass Density of Photon with Wavelength
Dhobi, S. H., Yadav, K., & Karki, B. (2021) · Indian Journal of Advanced Physics · doi:10.35940/ijap.b1003.101221 · Cited by 2
An Experiment to Determine Whether Electromagnetic Waves have MassPreprint
Newstead, M. A., & Newstead, S. C. (2011) · viXra
Interactive Lagrangian density between massive photons and gravitons
Deng, & Yanbin (2006) · 重庆大学学报：英文版
High-resolution spectroscopic frequency measurements
Maddaloni, P., Bellini, M., & Natale, P. D. (2013) · CRC Press eBooks · doi:10.1201/b14783-10
One hundred years of the photon
Milant’ev, V. P. (2005) · Uspekhi Fizicheskih Nauk · doi:10.3367/ufnr.0175.200511g.1233
Theoretical Analysis of Photon Quality Based on Classical Electromagnetic Theory
王, 钰. (2018) · Modern Physics · doi:10.12677/mp.2018.86031
On the time dependence of the photon Compton wavelength
Fiordilino, E. (2022) · Indian Journal of Physics · doi:10.1007/s12648-022-02474-1
Test of the Coulomb’s Law and Limits on the Mass of the Photon
Lacava, F. (2022) · Undergraduate lecture notes in physics · doi:10.1007/978-3-031-05099-2_15
The time and the growth in physics
Yandza, M. J. O. (2023) · International Journal of Physics Research and Applications · doi:10.29328/journal.ijpra.1001049
“We precise that in this article we consider a photon (particle of light) as a particle with mass [9] (we will calculate its value later).”
BackgroundQuantum Transitions in GEONsPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/5rnuw
The Interaction of Light with Non-Linear Gravitational FieldsPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/4y6ap
Gravitational LensingPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/3yu6n
GEON particle, the missing link between Quantum Physics and General RelativityPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/76g8m
Gravitational Waves. Introduction to the Gravitational Wave EquationPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/bfygp
Quantum GravityPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/p6n3w
Beyond Quantum Field TheoryPreprint
Vegt, W. (2023) · doi:10.31219/osf.io/d2qs4
The Physical Properties of Gravitational Waves Based on “Universal Equilibrium”Preprint
Vegt, W. (2023) · doi:10.31219/osf.io/9d2qe
Do Intergalactic Photons Attract or Repel Each Other?
Torres‐Silva, H., & Souza-de-Assis, A. (2017) · Científica · doi:10.46842/ipn.cien.v21n1a06
E=MC2 And E2=m2c4 p2c2 Are Not Valid: New Sources Of Energy From LightPreprint
Nwogugu, M. C. I. (2024) · SSRN Electronic Journal · doi:10.2139/ssrn.4770978
Tavakoli, M., & Moayedi, S. K. (2024) · Iranian Journal of Science · doi:10.1007/s40995-024-01639-3
“On the other hand, in classical electrody-namics photon is a massless particle which can be described by Maxwell equations (Tu et al. 2005; L.-C. Tu and 2004; Goldhaber and Nieto 2010).”
The Cosmic Void surrounding our GalaxyPreprint
Vegt, W. (2024) · doi:10.31219/osf.io/5pgt3
WITHDRAWNPreprint
Vegt, W. (2024) · doi:10.31234/osf.io/fvd8e
Can a Free Electron Absorb a Photon?
Nyambuya, G. G., Abbey, G. F., Simfukwe, J., Phiri, S. P., Simpemba, P. C., & Srivastava, A. (2025) · International Journal of Astronomy and Astrophysics · doi:10.4236/ijaa.2025.152012
Relativity of Mass: Mass Can Decrease With Velocity
Kumar, A. (2026) · PHYSICS Journal Theoretical and Experimental Studies · doi:10.64978/pjtes.2026.0526007
The Essence and Nature of the Speed of Light: A Fundamental Constant Emerging from Vacuum Structure
Butto, N. (2025) · Journal of High Energy Physics Gravitation and Cosmology · doi:10.4236/jhepgc.2025.113069
Yukawa Cut-Offs to Model the Muon Self-Interaction
Georgiev, M. (2025) · Contemporary Mathematics · doi:10.37256/cm.6420256240
“Which-Slit” Disclosure Without Decoherence Via Quantal Theory of Gravity (QTG)Preprint
Yarman, O., Kholmetskii, A. L., & Yarman, T. (2025) · SSRN Electronic Journal · doi:10.2139/ssrn.5362169
Force Acting on the Photon. Elementary Theory and Astrophysical Implications
Saiyan, G. A. (2025) · Journal of High Energy Physics Gravitation and Cosmology · doi:10.4236/jhepgc.2025.114079
Milyukov, V. K. (2025) · Springer proceedings in physics · doi:10.1007/978-981-96-7803-7_1
The dark photon: A 2025 perspective
Caputo, A., & Essig, R. (2026) · Elsevier eBooks · doi:10.1016/b978-0-443-26598-3.00059-6
The Dark Photon: a 2026 PerspectivePreprint
Caputo, A., & Essig, R. (2026) · arXiv (Cornell University) · doi:10.48550/arxiv.2603.08430
“These so-called Cavendish-type experiments have also been used to constrain the photon rest mass [117], and o ff er sensitivity to longer length scales, around ∼ 10cm, corresponding to smaller dark photon masses.”
Electromagnétisme non-maxwellien en astrophysique et applications spatiales à très basses fréquences
Bonetti, L. (2016) · theses.fr (ABES) · doi:10.70675/25307852z8679z41a2za845z515341a88381
Champs quantiques massifs en espace-temps courbe et tenseur d’impulsion-énergie renormalisé
Belokogne, A. (2016) · theses.fr (ABES) · doi:10.70675/b974c339z04faz4cf3zaf5dzfec04d215cbd
Small-Scale Gravitational Anomaly Induced by Peculiar Massive Photon Dynamics
Kumar, H., Pourhassan, B., Farahani, H., & Upadhyay, S. (2026) · Foundations of Physics · doi:10.1007/s10701-026-00932-y
Moawad, E. Y. (2026) · Next research. · doi:10.1016/j.nexres.2026.101949
Reinterpretation of the Blackbody Radiation Problem Based on the Unified Complex System Theory
Weicheng, C. U. I. (2026) · European journal of applied sciences · doi:10.14738/ejas.1403.11977
Yarman, T., Kholmetskii, A. L., Yarman, O., & Marchal, C. B. (2026) · Frontiers in Quantum Science and Technology · doi:10.3389/frqst.2026.1780610
Four-Dimensional Electrodynamics of a Bound Photon StatePreprint
Kazakov, V. (2026) · doi:10.24108/preprints-3116537
Kouzalis, A., & Antoniou, A. (2026) · International Journal of Physics Research and Applications · doi:10.29328/journal.ijpra.1001166
“Tu et al. (2005) [3] describe a con(cid:976)iguration involving (cid:976)ive concentric icosahedral shells, with a 4 MHz excitation at approximately 10 kV peak-to-peak and a resonant drive using a water-cooled high-Q coil.”
Gauge Invariance of Sedeonic Klein-Gordon EquationPreprint
Mironov, V. L., & Mironov, S. V. (2015) · viXra
Metadata
- 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
- 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
- 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
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
