M T Murphy et al., Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra, Monthly Notices Of The Royal Astronomical Society, 2003.
We have previously presented evidence for a varying fine-structure constant, α, in two independent samples of Keck/HIRES quasi-stellar object (QSO) absorption spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2< z abs< 3.7. The results, with raw statistical errors, indicate a smaller weighted mean α in the absorption clouds: Δα/α=(− 0.574±0.102)× …
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Manoj Kaplinghat et al., Constraining variations in the fine-structure constant with the cosmic microwave background, Physical Review D, 1999 92939159-C8E1-4D95-A90F-A7FDC5D9E6BC, 60 (2) p. 023516.
Any time variation in the fine-structure constant alters the ionization history of the universe and therefore changes the pattern of cosmic microwave background fluctuations. We calculate the changes in the spectrum of these fluctuations as a function of the change in $\ensuremath{\alpha}$, and we find that these changes are dominated by the change in the redshift of recombination due to the shift in the binding energy of hydrogen. We estimate the accuracy with which the next generation of cosmic microwave background experiments might constrain any variation in $\ensuremath{\alpha}$ at $z\ensuremath{\sim}1000$. We find that such experiments could potentially be sensitive to $|\ensuremath{\Delta}\ensuremath{\alpha}/\ensuremath{\alpha}|\ensuremath{\sim}{10}^{\ensuremath{-}2}\ensuremath{-}{10}^{\ensuremath{-}3}$.
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Freeman J Dyson, Time Variation of the Charge of the Proton, Physical Review Letters, 19 (1967) 1291-1293.
From the terrestrial occurrence of the nuclei ${\mathrm{Re}}^{187}$ and ${\mathrm{Os}}^{187}$, it is deduced that the elementary unit of charge $e$ cannot have varied by as much as one part in 1600 during the history of the earth.
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V A Dzuba et al., Space-Time Variation of Physical Constants and Relativistic Corrections in Atoms, Physical Review Letters, 82 (1999) 888-891.
High-redshift absorption systems detected in the optical spectra of quasars provide a powerful tool for constraining possible spatial and temporal variations of physical ``constants'' in the Universe. It is demonstrated that high sensitivity to the variation of the fine structure constant $\ensuremath{\alpha}$ can be obtained from a comparison of the spectra of heavy and light atoms. We have performed calculations for Mg I, Mg II, Cr II, and Fe II for which accurate quasar and laboratory spectra are available. Some possibilities for observing enhanced effects in variations of the fundamental constants in laboratory measurements are also discussed.
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A I SHLYAKHTER, Direct test of the constancy of fundamental nuclear constants, Nature, 264 (1976) 340-340.
THE possibility that fundamental nuclear constants may vary slowly while the Universe expands has been discussed by several authors1–5. I try here to show that the well known resonance properties of the ‘heavy nucleus plus slow neutron’ system make it a sensitive ‘receiver’, sharply tuned to the current values of nuclear constants.
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Michael R Wilczynska et al., Four direct measurements of the fine-structure constant 13 billion years ago, Science Advances, 2020 987AA35E-3E5F-454A-8DAD-7DFB13ECD078, 6 (17) p. eaay9672.
Observations of the redshift z = 7.085 quasar J1120+0641 are used to search for variations of the fine structure constant, a, over the redshift range 5:5 to 7:1. Observations at z = 7:1 probe the physics of the universe at only 0.8 billion years old. These are the most distant direct measurements of a to date and the first measurements using a near-IR spectrograph. A new AI analysis method is employed. Four measurements from the x-shooter spectrograph on the Very Large Telescope (VLT) constrain changes in a relative to the terrestrial value (α0). The weighted mean electromagnetic force in this location in the universe deviates from the terrestrial value by Δα/α = (αz − α0)/α0 = (−2:18 ± 7:27) × 10−5, consistent with no temporal change. Combining these measurements with existing data, we find a spatial variation is preferred over a no-variation model at the 3:9σ level.
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Edward Teller, On the Change of Physical Constants, Physical Review, 73 (1948) 801-802.
Phys. Rev. 73, 801 (1948)
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P A M Dirac, The Cosmological Constants, Nature, 139 (1937) 323-323.
THE fundamental constants of physics, such as c the velocity of light, h Planck's constant, e the charge and m mass of the electron, and so on, provide for us a set of absolute units for measurement of distance, time, mass, etc. There are, however, more of these constants than are necessary for this purpose, with the result that certain dimensionless numbers can be constructed from them. The significance of these numbers has excited much interest in recent times, and Eddington has set up a theory for calculating each of them purely deductively. Eddington's arguments are not always rigorous, and, while they give one the feeling that they are probably substantially correct in the case of the smaller numbers (the reciprocal fine-structure constant hc/e2 and the ratio of the mass of the proton to that of the electron), the larger numbers, namely the ratio of the electric to the gravitational force between electron and proton, which is about 1039, and the ratio of the mass of the universe to the mass of the proton, which is about 1078, are so enormous as to make one think that some entirely different type of explanation is needed for them.
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G Gamow, Electricity, Gravity, and Cosmology, Physical Review Letters, 19 (1967) 759-761.
Phys. Rev. Lett. 19, 759 (1967)
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Thibault Damour and Freeman J Dyson, The Oklo bound on the time variation of the fine-structure constant revisited, Nuclear Physics B, 480 (1996) 37-54.
It has been pointed out by Shlyakhter that data from the natural fission reactors which operated about two billion years ago at Oklo (Gabon) had the potential of providing an extremely tight bound on the variability of the fine-structure constant alpha. We revisit the derivation of such a bound by: (i) reanalyzing a large selection of published rare-earth data from Oklo, (ii) critically taking into account the very large uncertainty of the temperature at which the reactors operated, and (iii) connecting in a new way (using isotope shift measurements) the Oklo-derived constraint on a possible shift of thermal neutron-capture resonances with a bound on the time variation of alpha. Our final (95% C.L.) results are: -0.9 \times 10^{-7} <(alpha^{Oklo} - alpha^{now})/alpha <1.2\times 10^{-7} and -6.7 \times 10^{-17} {yr}^{-1} < {\dot alpha}^{averaged}/alpha <5.0\times10^{-17} {yr}^{-1}$.
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Asimina Arvanitaki et al., Resonant absorption of bosonic dark matter in molecules, Arxiv.Org, 2017 1709.05354, hep-ph (4) p. 522.
We propose a new class of bosonic dark matter (DM) detectors based on resonant absorption onto a gas of small polyatomic molecules. Bosonic DM acts on the molecules as a narrow-band perturbation, like an intense but weakly coupled laser. The excited molecules emit the absorbed energy into fluorescence photons that are picked up by sensitive photodetectors with low dark count rates. This setup is sensitive to any DM candidate that couples to electrons, photons, and nuclei, and may improve on current searches by several orders of magnitude in coupling for DM masses between 0.2 eV and 20 eV. This type of detector has excellent intrinsic energy resolution, along with several control variables---pressure, temperature, external electromagnetic fields, molecular species/isotopes---that allow for powerful background rejection methods as well as precision studies of a potential DM signal. The proposed experiment does not require usage of novel exotic materials or futuristic technologies, relying instead on the well-established field of molecular spectroscopy, and on recent advances in single-photon detection. Cooperative radiation effects, which arise due to the large spatial coherence of the nonrelativistic DM field in certain detector geometries, can tightly focus the DM-induced fluorescence photons in a direction that depends on the DM's velocity, possibly permitting a detailed reconstruction of the full 3D velocity distribution in our Galactic neighborhood, as well as further background rejection.
Published in: Phys. Rev. X 8, 041001 (2018)
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Luke A Barnes, A Reasonable Little Question: A Formulation of the Fine-Tuning Argument, Ergo, An Open Access Journal Of Philosophy, 6 (2019) 1-38.
A new formulation of the Fine-Tuning Argument (FTA) for the existence of God is offered, which avoids a number of commonly raised objections. I argue that we can and should focus on the fundamental constants and initial conditions of the universe, and show how physics itself provides the probabilities that are needed by the argument. I explain how this formulation avoids a number of common objections, specifically the possibility of deeper physical laws, the multiverse, normalisability, whether God would fine-tune at all, whether the universe is too fine-tuned, and whether the likelihood of God creating a life-permitting universe is inscrutable.
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J D Barrow et al., A Cosmological Tale of Two Varying Constants, Arxiv.Org, astro-ph (2002) 201-210.
We formulate a simple extension of general relativity which incorporates space-time variations in the Newtonian gravitation 'constant', G, and the fine structure 'constant', α , which generalises Brans-Dicke theory and our theory of varying α . We determine the behaviour of Friedmann universes in this theory. In the radiation and dust-dominated eras α G approaches a constant value and the rate of variation of α is equal to the magnitude of the rate of variation in G. The expansion dynamics of the universe are dominated by the variation of G but the variation of G has significant effects upon the time variation of α . Time variations in α are extinguished by the domination of the expansion by spatial curvature or quintessence fields, as in the case with no G variation.
Published in: Phys.Lett.B541:201-210,2002
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John D Barrow, Varying Constants, Arxiv.Org, astro-ph (2005) 2139-2153.
We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that are consistent with time-variation in the fine structure 'constant' since a redshift of 3.5. The behaviour of a simple class of varying-alpha cosmologies is outlined in the light of all the observational constraints.
Published in: Phil.Trans.Roy.Soc.Lond.A363:2139-2153,2005
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John D Barrow, Cosmological bounds on spatial variations of physical constants, Physical Review D, 71 (2005) 58-7.
We derive strong bounds on any possible large-scale spatial variation in the values of physical constants whose space-time evolution is driven by a scalar field. These limits are imposed by the isotropy of the microwave background on large angular scales in theories which describe space and time variations in the fine structure constant, , the electron-proton mass ratio, , and the Newtonian gravitational constant, G. Large-scale spatial fluctuations in the fine structure constant are bounded by = & 2 109 and = & 1:2 108 in the Bekenstein-Sandvik-Barrow-Magueijo and varying-speed-of-light theories, respectively, fluctuations in the electron-proton mass ratio by = & 9 105 in the Barrow-Magueijo theory and fluctuations in G by G=G & 3:6 1010 in the Brans-Dicke theory. These derived bounds are significantly stronger than any obtainable by direct observations of astrophysical objects at the present time.
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John D Barrow and Baojiu Li, Varying-alpha cosmologies with potentials, Physical Review D, 78 (2008) 463-16.
We generalize the Bekenstein-Sandvik-Barrow-Magueijo model for the variation of the fine-structure ‘‘constant,’’ , to include an exponential or inverse power-law self-potential for the scalar field ’ which drives the time variation of , and consider the dynamics of ’ in such models. We find solutions for the evolution of ’ or in matter-, radiation-, and dark-energy-dominated cosmic eras. In general, the evolution of ’ is well determined solely by either the self-potential or the coupling to matter, depending on the model parameters. The results are general and applicable to other models where the evolution of a scalar field is governed by a matter coupling and a self-potential. We find that the existing astronomical data stringently constrains the possible evolution of between redshifts z ’ 1–3:5 and the present, and this leads to a very strong limit on the allowed deviation of the potential from that of a pure cosmological constant.
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John D Barrow and Douglas J Shaw, Varying Alpha: New Constraints from Seasonal Variations, Arxiv.Org, 2008 0806.4317, hep-ph (6) p. 463.
We analyse the constraints obtained from new atomic clock data on the possible time variation of the fine structure `constant' and the electron-proton mass ratio and show how they are strengthened when the seasonal variation of Sun's gravitational field at the Earth's surface is taken into account. We compare these bounds with those obtainable from tests of the Weak Equivalence Principle and high-redshift observations of quasar absorption spectra consistent with time variations in the fine structure constant.
Published in: Phys.Rev.D78:067304,2008
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John D Barrow and Sean Z W Lip, Generalized theory of varying alpha, Physical Review D, 85 (2012) 131-12.
In this paper, we formulate a generalization of the simple Bekenstein-Sandvik-Barrow-Magueijo theory of varying alpha by allowing the coupling constant ! for the corresponding scalar field c to depend on c . We focus on the situation where ! is exponential in c and find the late-time behaviors that occur in matter-dominated and dark-energy dominated cosmologies. We also consider the situation when the background expansion scale factor of the Universe evolves in proportion to an arbitrary power of the cosmic time. We find the conditions under which the fine-structure ‘‘constant’’ increases with time, as in the Bekenstein-Sandvik-Barrow-Magueijo theory, and establish a cosmic no-hair behavior for accelerat- ing universes. We also find the conditions under which the fine-structure constant can decrease with time and compare the whole family of models with astronomical data from quasar absorption spectra.
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John D Barrow and David Sloan, Bouncing Anisotropic Universes with Varying Constants, Arxiv.Org, 2013 1304.6699v1, gr-qc (2) p. 51.
We examine the evolution of a closed, homogeneous and anisotropic cosmology subject to a variation of the fine structure 'constant', , within the context of the theory introduced by Bekenstein, Sandvik, Barrow and Magueijo, which generalises Maxwell's equations and general relativity. The variation of permits an effective ghost scalar field, whose negative energy density becomes dominant at small length scales, leading to a bouncing cosmology. A thermodynamically motivated coupling which describes energy exchange between the effective ghost field and the radiation field leads to an expanding, isotropizing sequence of bounces. In the absence of entropy production we also find solutions with stable anisotropic oscillations around a static universe.
Published in: Phys. Rev. D 88, 023518 (2013)
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John D Barrow and Alexander A H Graham, General dynamics of varying-alpha universes, Physical Review D, 88 (2013) 1150-21.
We introduce and study extensions of the varying alpha theory of Bekenstein-Sandvik-Barrow- Magueijo to allow for an arbitrary coupling function and self-interaction potential term in the theory. We study the full evolution equations without assuming that variations in alpha have a negligible effect on the expansion scale factor and the matter density evolution, as was assumed in earlier studies. The background Friedmann-Robertson-Walker cosmology of this model in the cases of zero and nonzero spatial curvature is studied in detail, using dynamical systems techniques, for a wide class of potentials and coupling functions. All the asymptotic behaviors are found, together with some new solutions. We study the cases where the electromagnetic parameter, zeta, is positive and negative, corresponding to magnetic and electrostatic energy domination in the nonrelativistic matter. In particular, we investigate the cases where the scalar field driving alpha variations has exponential and power-law self-interaction potentials and the behavior of theories where the coupling constant between matter and alpha variations is no longer a constant.
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John D Barrow and João Magueijo, Redshifting of cosmological black bodies in Bekenstein-Sandvik-Barrow-Magueijo varying-alpha theories, Physical Review D, 90 (2014) 123506-7.
We analyze the behavior of blackbody radiation in theories of electromagnetism which allow the electron charge and the fine structure constant to vary in space and time. We show that such theories can be expressed as relativistic generalizations of a conventional dielectric. By making the appropriate definition of the vector potential and associated gauge transformations, we can identify the equivalent of the electric and displacement fields, E and D, as well as the magnetic B and H fields. We study the impact of such dielectrics on the propagation of light in the so-called “BSBM” theory. We examine the form of simple cosmological solutions and conclude that no changes are created to the standard cosmological evolution of the temperature and energy density of blackbody radiation. Nonetheless the matter evolution changes and the behavior of the entropy per baryon is modified, and the ratios of different dark matter components may be changed too.
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J D Bekenstein, Fine Structure Constant: Is It Really a Constant?, Phys. Rev., D25 (1982) 1527-1539.
It is often claimed that the fine-structure "constant" $\ensuremath{\alpha}$ is shown to be strictly constant in time by a variety of astronomical and geophysical results. These constrain its fractional rate of change $\frac{\stackrel{\ifmmode \dot{}\else \.{}\fi{}}{\ensuremath{\alpha}}}{\ensuremath{\alpha}}$ to at least some orders of magnitude below the Hubble rate ${H}_{0}$. We argue that the conclusion is not as straightforward as claimed since there are good physical reasons to expect $\frac{\stackrel{\ifmmode \dot{}\else \.{}\fi{}}{\ensuremath{\alpha}}}{\ensuremath{\alpha}}\ensuremath{\ll}{H}_{0}$. We propose to decide the issue by constructing a framework for $\ensuremath{\alpha}$ variability based on very general assumptions: covariance, gauge invariance, causality, and time-reversal invariance of electromagnetism, as well as the idea that the Planck-Wheeler length (${10}^{\ensuremath{-}33}$ cm) is the shortest scale allowable in any theory. The framework endows $\ensuremath{\alpha}$ with well-defined dynamics, and entails a modification of Maxwell electrodynamics. It proves very difficult to rule it out with purely electromagnetic experiments. In a cosmological setting, the framework predicts an $\frac{\stackrel{\ifmmode \dot{}\else \.{}\fi{}}{\ensuremath{\alpha}}}{\ensuremath{\alpha}}$ which can be compatible with the astronomical constraints; hence, these are too insensitive to rule out $\ensuremath{\alpha}$ variability. There is marginal conflict with the geophysical constraints; however, no firm decision is possible because of uncertainty about various cosmological parameters. By contrast the framework's predictions for spatial gradients of $\ensuremath{\alpha}$ are in fatal conflict with the results of the E\"otv\"os-Dicke-Braginsky experiments. Hence these tests of the equivalence principle rule out with confidence spacetime variability of $\ensuremath{\alpha}$ at any level.
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Jacob D Bekenstein, Fine-structure constant variability, equivalence principle, and cosmology, Physical Review D, 66 (2002) 884-17.
It has been widely believed that variability of the fine-structure constant would imply detectable violations of the weak equivalence principle. This belief is not justified in general. It is put to rest here in the context of the general framework for variability J. D. Bekenstein, Phys. Rev. D 25, 1527 1982 in which the exponent of a scalar field plays the role of the permittivity and inverse permeability of the vacuum. The coupling of particles to the scalar field is necessarily such that the anomalous force acting on a charged particle by virtue of its mass’s dependence on the scalar field is canceled by terms modifying the usual Coulomb force. As a consequence a particle’s acceleration in external fields depends only on its charge to mass ratio, in accordance with the principle. And the center of mass acceleration of a composite object can be proved to be independent of the object’s internal constitution, as the weak equivalence principle requires. Likewise the widely employed assumption that the Coulomb energy of matter is the principal source of the scalar field proves wrong; Coulomb energy effectively cancels out in the continuum description of the scalar field’s dynamics. This cancellation resolves a cosmological conundrum: with Coulomb energy as the source of the scalar field, the framework would predict a decrease of with cosmological expansion, whereas an increase is claimed to be observed. Because of the said cancellation, magnetic energy of cosmological baryonic matter is the main source of the scalar field. Consequently the expansion is accompanied by an increase in ; for reasonable values of the framework’s sole parameter, this occurs at a rate consistent with the observers’ claims.
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Jacob D Bekenstein and Marcelo Schiffer, Varying fine structure “constant” and charged black holes, Physical Review D, 80 (2009) 1150-12.
Speculation that the fine-structure constant varies in spacetime has a long history. We derive, in 4-D general relativity and in isotropic coordinates, the solution for a charged spherical black hole according to the framework for dynamical J. D. Bekenstein, Phys. Rev. D 25, 1527 (1982).. This solution coincides with a previously known one-parameter extension of the dilatonic black hole family. Among the notable properties of varying- charged black holes are adherence to a ‘‘no hair’’ principle, the absence of the inner (Cauchy) horizon of the Reissner-Nordstro ̈m black holes, the nonexistence of precisely extremal black holes, and the appearance of naked singularities in an analytic extension of the relevant metric. The exteriors of almost extremal electrically (magnetically) charged black holes have simple structures which makes their influence on applied magnetic (electric) fields transparent. We rederive the thermodynamic functions of the modified black holes; the otherwise difficult calculation of the electric potential is done by a shortcut. We confirm that variability of in the wake of expansion of the universe does not threaten the generalized second law.
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Jacob Bekenstein and Marcelo Schiffer, Varying fine structure "constant" and charged black holes, Physical Review D, 2009 vol. 80 (12) p. 123508.
Speculation that the fine-structure constant α varies in spacetime has a long history. We derive, in 4-D general relativity and in isotropic coordinates, the solution for a charged spherical black hole according to the framework for dynamical α J. D. Bekenstein, Phys. Rev. D 25, 1527 (1982).. This solution coincides with a previously known one-parameter extension of the dilatonic black hole family. Among the notable properties of varying-α charged black holes are adherence to a “no hair” principle, the absence of the inner (Cauchy) horizon of the Reissner-Nordström black holes, the nonexistence of precisely extremal black holes, and the appearance of naked singularities in an analytic extension of the relevant metric. The exteriors of almost extremal electrically (magnetically) charged black holes have simple structures which makes their influence on applied magnetic (electric) fields transparent. We rederive the thermodynamic functions of the modified black holes; the otherwise difficult calculation of the electric potential is done by a shortcut. We confirm that variability of α in the wake of expansion of the universe does not threaten the generalized second law.
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J C Berengut et al., Limits on the Dependence of the Fine-Structure Constant on Gravitational Potential from White-Dwarf Spectra, Physical Review Letters, 111 (2013) 1-5.
We propose a new probe of the dependence of the fine-structure constant on a strong gravitational field using metal lines in the spectra of white-dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white-dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits of = 1⁄4 ð4:2 1:6Þ 105 and ð6:1 5:8Þ 105 from FeV and NiV spectra, respectively, at a dimensionless gravitational potential relative to Earth of 0 %5 could be improved by up to 2 orders of magnitude.
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Marcelo S Berman and Luis A Trevisan, On a time varying fine structure constant, Arxiv.Org, 2001 gr-qc/0111102, gr-qc.
By employing Dirac LNH, and a further generalization by Berman (GLNH), we estimate how should vary the total number of nucleons, the energy density, Newton Gravitational constant, the cosmological constant, the magnetic permeability and electric permitivity, of the Universe,in order to account for the experimentally observed time variation of the fine structure constant. As a bonus,we find an acceptable value for the deceleration parameter of the present Universe, compatible with the Supernovae observations.
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Cheng Chin et al., Ultracold molecules: new probes on the variation of fundamental constants, New Journal Of Physics, 11 (2009) 055048-15.
Ultracold molecules offer brand new opportunities to probe the variation of fundamental constants with unprecedented sensitivity. This paper summarizes theoretical background and current constraints on the variation of the fine structure constant and electron-to-proton mass ratio, as well as proposals and experimental efforts to measure the variations based on ultracold molecules. In particular, we describe two novel spectroscopic schemes on ultracold molecules that have greatly enhanced sensitivity to fundamental constants: resonant scattering near Feshbach resonances and spectroscopy on close-lying energy levels of ultracold molecules.
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Mariusz P Dąbrowski et al., New tests of variability of the speed of light., Epj Web Of Conferences, 126 (2016) 04012-11.
We present basic ideas of the varying speed of light cosmology, its formulation, benefits and problems. We relate it to the theories of varying fine structure constants and discuss some new tests (redshift drift and angular diameter distance maximum) which may allow measuring timely and spatial change of the speed of light by using the future missions such as Euclid, SKA (Square Kilometer Array) or others.
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Thibault Damour, Questioning the Equivalence Principle, Arxiv.Org, gr-qc (2001) 1249-1256.
The Equivalence Principle (EP) is not one of the ``universal'' principles of physics (like the Action Principle). It is a heuristic hypothesis which was introduced by Einstein in 1907, and used by him to construct his theory of General Relativity. In modern language, the (Einsteinian) EP consists in assuming that the only long-range field with gravitational-strength couplings to matter is a massless spin-2 field. Modern unification theories, and notably String Theory, suggest the existence of new fields (in particular, scalar fields: ``dilaton'' and ``moduli'') with gravitational-strength couplings. In most cases the couplings of these new fields ``violate'' the EP. If the field is long-ranged, these EP violations lead to many observable consequences (variation of ``constants'', non-universality of free fall, relative drift of atomic clocks,...). The best experimental probe of a possible violation of the EP is to compare the free-fall acceleration of different materials.
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A Derevianko and M Pospelov, Hunting for topological dark matter with atomic clocks, Nature Physics, 10 (2014) 933-936.
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Gia Dvali and Matias Zaldarriaga, Changing alpha with time: implications for fifth-force-type experiments and quintessence., Physical Review Letters, 2002 11863992, 88 (9) p. 091303.
If the recent observations suggesting a time variation of the fine structure constant are correct, they imply the existence of an ultralight scalar particle. This particle inevitably couples to nucleons through the alpha dependence of their masses and thus mediates an isotope-dependent long-range force. The strength of the coupling is within a couple of orders of magnitude of the existing experimental bounds for such forces. The new force can be potentially measured in precision experimental tests of the equivalence principle. Because of a coincidence of the required time scales, the scalar field can at the same time play the role of a quintessence field.
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V A Dzuba et al., Calculations of the relativistic effects in many electron atoms and space-time variation of fundamental constants, Arxiv Preprint, A59 (1999) 230-237.
Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variation of physical ‘‘constants’’ in the Universe. Detection of high-redshift absorption systems intersecting the sight lines towards distant quasars provides a powerful tool for measuring these variations. We have previously demon- strated that high sensitivity to the variation of the fine-structure constant can be obtained by comparing spectra of heavy and light atoms or molecules. Here we describe new calculations for a range of atoms and ions, most of which are commonly detected in quasar spectra: Fe II, Mg II, Mg I, C II, C IV, N V, O I, Al III, Si II, Si IV, Ca I, Ca II, Cr II, Mn II, Zn II, Ge II see the results in Table III. The combination of Fe II and Mg II, for which accurate laboratory frequencies exist, has already been used to constrain variations. To use other atoms and ions, accurate laboratory values of frequencies of the strong E1 transitions from the ground states are required. We wish to draw the attention of atomic experimentalists to this important problem. We also discuss a mechanism which can lead to a greatly enhanced sensitivity for placing constraints on variation on fundamental constants. Calculations have been performed for Hg II, Yb II, Ca I, and Sr II where there are optical transitions with the very small natural widths, and for hyperfine transition in Cs I and Hg II.
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V A Dzuba et al., Relativistic effects in Ni II and the search for variation of the fine-structure constant, Physical Review A, 63 (2001) 489-5.
Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variation of physical ‘‘constants’’ in the Universe. Detection of high redshift absorption systems intersecting the sight lines toward distant quasars provides a powerful tool for measuring these variations. In the present paper we demonstrate that high sensitivity to variation of the fine-structure constant can be obtained by comparing cosmic and laboratory spectra of the Ni II ion. Relativistic effects in Ni II reveal many interesting features. The Ni II spectrum exhibits avoided level crossings under variation of and the intervals between the levels have strong nonlinear dependencies on relativistic corrections. The values of the transition frequency shifts, due to the change of , vary significantly from state to state including changes of sign. This enhances the sensitivity to the variation of and reduces possible systematic errors. Calculations of the dependence of the nickel ion spectral lines that are detectable in quasar absorption spectra have been performed using a relativistic configu- ration interaction method.
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V A Dzuba and V V Flambaum, Fine-structure anomalies and search for variation of the fine-structure constant in laboratory experiments, Physical Review A, 72 (2005) 052514-4.
The configuration interaction in many-electron atoms may cause anomalies in the fine structure which make the intervals small and very sensitive to variation of the fine-structure constant. Repeated precision measure- ments of these intervals over a long period of time can put strong constraints on possible time variation of the fine-structure constant. We consider the 5p4 3P2,1,0 fine-structure multiplet in the ground state of neutral tellurium as an example. Here the effect of change of the fine structure constant is enhanced about 100 times in the relative change of the small energy interval between the 3P1 and 3P0 states.
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V V Flambaum and A F Tedesco, Dependence of nuclear magnetic moments on quark masses and limits on temporal variation of fundamental constants from atomic clock experiments, Physical Review-Section C-Nuclear Physics, 73 (2006) 344-9.
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Guilherme Franzmann, Varying fundamental constants: a full covariant approach and cosmological applications, Arxiv.Org, 2017 1704.07368, gr-qc.
We build a minimal extension of General Relativity in which Newton's gravitational coupling, G, the speed of light, c, and the cosmological constant, Λ, are spacetime variables. This is done while satisfying the contracted Bianchi identity as well as the local conservation of energy momentum tensor. A dynamical constraint is derived, which shows that variations of G and c are coupled to the local matter-energy physical content, while variation of Λ is coupled to the local geometry. This constraint presents a natural cosmological screening mechanism that brings new perspective concerning the current observations of a cosmological constant, Λ0 in cosmological observations. We also explore early universe background cosmology and show that the proposal provides alternatives to obtain an accelerated expansion, similar to those coming from Varying Speed of Light theories.
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Thibaut Josset et al., Dark Energy from Violation of Energy Conservation, Physical Review Letters, 118 (2017) 715-5.
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S G Karshenboim, Fundamental physical constants: looking from different angles, Canadian Journal Of Physics, 83 (2005) 767-811.
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Dagny Kimberly and João Magueijo, Varying alpha and the electroweak model, Physics Letters B, 584 (2004) 8-15.
Inspired by recent claims for a varying fine structure constant, alpha, we investigate the effect of “promoting coupling constants to variables” upon various parameters of the standard model. We first consider a toy model: Proca theory of the massive photon. We then explore the electroweak theory with one and two dilaton fields. We find that a varying alpha unavoidably implies varying W and Z masses. This follows from gauge invariance, and is to be contrasted with Proca theory. For the two dilaton theory the Weinberg angle is also variable, but Fermi’s constant and the tree level fermion masses remain constant unless the Higgs potential becomes dynamical. We outline some cosmological implications.
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Rollin A King et al., Chemistry as a function of the fine-structure constant and the electron-proton mass ratio, Physical Review A, 81 (2010) 1095-9.
In standard computations in theoretical quantum chemistry the accepted values of the fundamental physical constants are assumed. Alternatively, the tools of computational quantum chemistry can be used to investigate hypothetical chemistry that would result from different values of these constants, given the same physical laws. In this work, the dependence of a variety of basic chemical quantities on the values of the fine-structure constant and the electron-proton mass ratio is explored. In chemistry, the accepted values of both constants may be considered small, in the sense that their increase must be substantial to seriously impact bond energies. It is found that if the fine-structure constant were larger, covalent bonds between light atoms would be weaker, and the dipole moment and hydrogen-bonding ability of water would be reduced. Conversely, an increase in the value of the electron-proton mass ratio increases dissociation energies in molecules such as H2, O2, and CO2. Specifically, a sevenfold increase in the fine-structure constant decreases the strength of the O–H bond in the water molecule by 7 kcal mol−1 while reducing its dipole moment by at least 10%, whereas a 100-fold increase in the electron-proton mass ratio increases the same bond energy by 11 kcal mol−1.
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Mikhail G Kozlov and Sergei A Levshakov, Microwave and submillimeter molecular transitions and their dependence on fundamental constants, Annalen Der Physik, 525 (2013) 452-471.
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S K Lamoreaux and J R Torgerson, Neutron moderation in the Oklo natural reactor and the time variation of α, Physical Review D, 69 (2004) 340-5.
In previous analyses of the Oklo Gabon natural reactor to test for a possible time variation of the fine- structure constant , a Maxwell-Boltzmann low energy neutron spectrum was assumed. We present here an analysis where a more realistic spectrum is employed and show that the most recent isotopic analysis of
samples implies a decrease in , over the last 2 109 regarding years since the reactor was operating, of (
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Susana J Landau et al., Early universe constraints on time variation of fundamental constants, Physical Review D, 78 (2008) 966-16.
We study the time variation of fundamental constants in the early Universe. Using data from primordial light nuclei abundances, cosmic microwave background, and the 2dFGRS power spectrum, we put constraints on the time variation of the fine structure constant and the Higgs vacuum expectation value hvi without assuming any theoretical framework. A variation in hvi leads to a variation in the electron mass, among other effects. Along the same line, we study the variation of and the electron mass me. In a purely phenomenological fashion, we derive a relationship between both variations.
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Anton A Lipovka and Ivan A Cardenas, Variation of the fine structure constant caused by the expansion of the Univerce, Arxiv.Org, 2016 1608.04593v4, physics.gen-ph.
In present paper we evaluate the fine structure constant variation, that should take place as the Universe expands and its curvature is changed adiabatically. Such variation of the fine structure constant is attributed to an energy losses by an extended physical system (consist of baryonic component and electromagnetic field) due to expansion of our Universe. Obtained ratio (d alpha)/alpha = 1. 10{-18} (per second) is only five times smaller than actually reported experimental limit on this value. For this reason obtained variation can probably be measured within a couple of years. To argue the correctness of our approach we calculate the Planck constant as adiabatic invariant of the electromagnetic field propagated on a manifold characterized by slowly varied geometry, in the framework of the pseudo- Riemannian geometry. Finally we discuss the double clock experiment based on Al+ and Hg+ clocks carried out by T. Rosenband et al. (Science 2008). We show that in this case (when the fine structure constant is changed adiabatically) the method based on double clock experiment can not be applied to measure the fine structure constant variation.
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Andrew Ludlow, Viewpoint: “Tweezer Clock” Offers New Possibilities in Timekeeping, Physics, 12 (2019) 1-4.
An optical clock based on an array of individually trapped atoms provides a new twist in atom-based timekeeping.
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Feng Luo et al., Gyromagnetic factors and atomic clock constraints on the variation of fundamental constants, Physical Review D, 84 (2011) 128-22.
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João Magueijo et al., Is it e or is it c? Experimental Tests of Varying Alpha, Arxiv.Org, astro-ph (2002) 284-289.
Is the recent evidence for a time-varying fine structure 'constant' α to be interpreted as a varying e, c, , or a combination thereof? We consider the simplest varying electric charge and varying speed of light theories (VSL) and prove that for the same type of dark matter they predict opposite senses of variation in α over cosmological times. We also show that unlike varying e theories, VSL theories do not predict violations of the weak equivalence principle (WEP). Varying e theories which explain astronomical inferences of varying α predict WEP violations only an order of magnitude smaller than existing E\"otv\"os experiment limits but could be decisively tested by STEP. We finally exhibit a set of atomic-clock and related experiments for which { all} (hyperbolic) varying α theories predict non-null results. They provide independent tests of the recent astronomical evidence.
Published in: Phys.Lett. B549 (2002) 284-289
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J Magueijo, Cosmology ‘Without’ Constants , Astrophys. Space Sci., 283 (2003) 493-503.
We review varying speed of light (VSL) theories, in a cosmological and astrophysical setting, and as phenomenological descriptions of quantum gravity. We first introduce two observational puzzles,...
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C J A P Martins et al., Dark energy and equivalence principle constraints from astrophysical tests of the stability of the fine-structure constant, Journal Of Cosmology And Astroparticle Physics, 2015 (2015) 047-047.
Astrophysical tests of the stability of fundamental couplings, such as the fine- structure constant α, are becoming an increasingly powerful probe of new physics. Here we discuss how these measurements, combined with local atomic clock tests and Type Ia supernova and Hubble parameter data, constrain the simplest class of dynamical dark en- ergy models where the same degree of freedom is assumed to provide both the dark energy and (through a dimensionless coupling, ζ, to the electromagnetic sector) the α variation. Specifically, current data tightly constrains a combination of ζ and the present dark energy equation of state w0. Moreover, in these models the new degree of freedom inevitably cou- ples to nucleons (through the α dependence of their masses) and leads to violations of the Weak Equivalence Principle. We obtain indirect bounds on the E ̈otv ̈os parameter η that are typically stronger than the current direct ones. We discuss the model-dependence of our re- sults and briefly comment on how the forthcoming generation of high-resolution ultra-stable spectrographs will enable significantly tighter constraints.
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C J A P Martins, The status of varying constants: a review of the physics, searches and implications, Reports On Progress In Physics, 80 (2017) 126902-46.
The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete—if not incorrect—and that new physics is out there, waiting to be discovered. A key task for the next generation of laboratory and astrophysical facilities is to search for, identify and ultimately characterize
this new physics. Here we highlight recent developments in tests of the stability of nature’s fundamental couplings, which provide a direct handle on new physics: a detection of variations will be revolutionary, but even improved null results provide competitive constraints on a range of cosmological and particle physics paradigms. A joint analysis of all currently available data shows a preference for variations of α and μ at about the two-sigma level, but inconsistencies between different sub-sets (likely due to hidden systematics) suggest that these statistical preferences need to be taken with caution. On the other hand, these measurements strongly constrain Weak Equivalence Principle violations. Plans and forecasts for forthcoming studies with facilities such as ALMA, ESPRESSO and the ELT, which should clarify these issues, are also discussed, and synergies with other probes are briefly highlighted. The goal
is to show how a new generation of precision consistency tests of the standard paradigm will soon become possible.
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C J A P Martins and A M M Pinho, Stability of fundamental couplings: A global analysis, Physical Review D, 95 (2017) 57-13.
Astrophysical tests of the stability of fundamental couplings are becoming an increasingly important probe of new physics. Motivated by the recent availability of new and stronger constraints we update previous works testing the consistency of measurements of the fine-structure constant α and the proton-to- electron mass ratio μ 1⁄4 mp=me (mostly obtained in the optical/ultraviolet) with combined measurements of α, μ and the proton gyromagnetic ratio gp (mostly in the radio band). We carry out a global analysis of all available data, including the 293 archival measurements of Webb et al. and 66 more recent dedicated measurements, and constraining both time and spatial variations. While nominally the full data sets show a slight statistical preference for variations of α and μ (at up to two standard deviations), we also find several inconsistencies between different subsets, likely due to hidden systematics and implying that these statistical preferences need to be taken with caution. The statistical evidence for a spatial dipole in the values of α is found at the 2.3 sigma level. Forthcoming studies with facilities such as ALMA and ESPRESSO should clarify these issues.
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J W Moffat, A Model of Varying Fine Structure Constant and Varying Speed of Light, Arxiv.Org, 2001 astro-ph/0109350, astro-ph.
The recent evidence for a cosmological evolution of the fine structure constant =e^2/ c found from an analysis of absorption systems in the spectra of distant quasars, is modelled by a cosmological scenario in which it is assumed that only the speed of light varies. The model fits the spectral line data and can also lead to a solution of the initial value problems in cosmology.
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Keith A Olive and Maxim Pospelov, Evolution of the Fine Structure Constant Driven by Dark Matter and the Cosmological Constant, Arxiv.Org, 2001 hep-ph/0110377, hep-ph (8) p. 323.
Bekenstein's model of a scalar field, , that affects the electromagnetic permeability (usually identified with ``changing '') predicts tiny variations of the effective fine structure constant up to very high red-shifts, |(z=3.5)/_0-1| < 10^{-10}, when the constraints from E\"otv\"os-Dicke-Braginsky types of experiments are imposed. We generalize this model by allowing additional couplings of to both a dark matter candidate and to the cosmological constant. We show that in a supersymmetric generalization of Bekenstein's model, the coupling to the LSP, which is assumed to contribute significantly to the dark matter density, can be up to six orders of magnitude stronger than the coupling to the baryon energy density. This allows one to evade the present limits on the non-universality of the gravitational attraction due to -exchange and at the same time accommodate the effective shift in at the level of (z=3.5)/_0-1 10^{-5}, reported recently from observations of quasar absorption spectra.
Published in: Phys.Rev.D65:085044,2002
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Keith A Olive, Variable Constants - A Theoretical Overview, Proceedings Of The International Astronomical Union, 5 (2010) 300-300.
In many theories of unified interactions, there are additional degrees of freedom which may allow for the variation of the fundamental constants of nature. I will review the motivation for such variations, and describe the theoretical relations between variations of gauge and Yukawa couplings.
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Lukáš F Pašteka et al., Material Size Dependence on Fundamental Constants, Physical Review Letters, 2019 vol. 122 (16) p. 160801.
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M S Safronova et al., Search for new physics with atoms and molecules, Reviews Of Modern Physics, 2018 vol. 90 (2) p. 025008.
This article reviews recent developments in tests of fundamental physics using atoms and molecules, including the subjects of parity violation, searches for permanent electric dipole moments, tests of the CPT theorem and Lorentz symmetry, searches for spatiotemporal variation of fundamental constants, tests of quantum electrodynamics, tests of general relativity and the equivalence principle, searches for dark matter, dark energy, and extra forces, and tests of the spin-statistics theorem. Key results are presented in the context of potential new physics and in the broader context of similar investigations in other fields. Ongoing and future experiments of the next decade are discussed.
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Haavard Bunes Sandvik, Varying Fundamental Constants in Cosmology , , .
We investigate the cosmological consequences of Bekenstein theory, in which the electric charge e takes on the value of a real scalar field. Cosmic string vortices in such theories are shown to act as source for variations in the electric charge, giving a significantly different value at the string core. The dielectric field arranges itself in the shape of a local string with a quantized magnetic flux presumably borrowing these features from the underlying Nielsen-Olesen vortex.
Furthermore we produce a self-consistent cosmological model from the Bekenstein theory. We show how this model can explain the recent evidence for a varying a, whilst still honouring constraints from fifth-force experiments. This is done by placing strong constraints upon the nature of the dark matter in the Universe. This cosmological model is investigated in detail, and it is shown, alongside Brans-Dicke theory, to motivate the formulation of novel anthropic considerations.
The link between non-minimally coupled scalar fields and weak equivalence princi- ple violations can be shown to imply striking experimental differences between different varying-Q! theories. We suggest ways in which this can be used to distinguish observa- tionally between varying e and varying c theories.
We also propose a self-consistent theory which combines our varying e theory with Brans-Dicke varying G theory. In this framework both a and G are allowed to vary simultaneously. The theory has similar behaviour to the constant G case, with G varying only a few percent through the history of the Universe.
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Douglas J Shaw and John D Barrow, Varying couplings in electroweak theory, Physical Review D, 71 (2005) 340-9.
We extend the theory of Kimberly and Magueijo for the spacetime variation of the electroweak couplings in the unified Glashow-Salam-Weinberg model of the electroweak interaction to include quantum corrections. We derive the effective quantum-corrected dilaton evolution equations in the presence of a background cosmological matter density that is composed of weakly interacting and non-weakly-interacting nonrelativistic dark-matter components.
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David Sloan, Loop quantum cosmology and the fine structure constant, Classical And Quantum Gravity, 31 (2013) 025014-14.
The cosmological implications of introducing a variation to the fine structure ‘constant’, α are examined within the context of loop quantum cosmology. The evolution of α is described using the model introduced by Bekenstein, Sandvik, Barrow and Magueijo, in which a ghost scalar field produces the variation. The dynamics of the system are examined in flat and closed cosmological settings. Matter consisting of the scalar field and radiation are examined with a thermodynamically motivated coupling between the two, which can lead to a series of bounces induced by both the negative density effects of the ghost field and the loop effects.
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Y V Stadnik and V V Flambaum, Searching for Dark Matter and Variation of Fundamental Constants with Laser and Maser Interferometry, Physical Review Letters, 114 (2015) 1024-6.
ny slight variations in the fundamental constants of nature, which may be induced by dark matter or some yet-to-be-discovered cosmic field, would characteristically alter the phase of a light beam inside an interferometer, which can be measured extremely precisely. Laser and maser interferometry may be applied to searches for the linear-in-time drift of the fundamental constants, detection of topological defect dark matter through transient-in-time effects, and for a relic, coherently oscillating condensate, which consists of scalar dark matter fields, through oscillating effects. Our proposed experiments require either minor or no modifications of existing apparatus, and offer extensive reach into important and unconstrained spaces of physical parameters.
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Jean-Philippe Uzan, Varying constants, gravitation and cosmology, Living Reviews In Relativity, 2011.
Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to mat- ter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of differ- ent constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.
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Jean-Philippe Uzan, The stability of fundamental constants, Comptes Rendus Physique, 16 (2015) 576-585.
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John K Webb et al., Search for Time Variation of the Fine Structure Constant, Physical Review Letters, 82 (1999) 884-887.
An order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant a. Applied to a sample of 30 absorption systems, spanning redshifts 0.5 , z , 1.6, we derive limits on variations in a over a wide range of epochs.
For the whole sample, Daa 21.1 6 0.4 3 10 25. This deviation is dominated by measurements 25 atz.1,whereDaa21.960.5310 . Forz,1,Daa20.260.4310 . While this is consistent with a time-varying a, further work is required to explore possible systematic errors in the data, although careful searches have so far revealed none.
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John K Webb et al., Further Evidence for Cosmological Evolution of the Fine Structure Constant, Physical Review Letters, 87 (2001) 205-4.
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John K Webb, Are the laws of the nature changing with time?, Phys. World, 16N4 (2003) 33-38.
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Von P Jordan, Die Physicalischen Weltkonstanten, Die Naturwissenschaften, 2020 pp. 1-5.
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