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The Oklo bound on the time variation of the fine-structure constant revisited
Abstract
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 α. 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 α. Our final (95% C.L.) results are: −0.9 × 10−7 < (αOklo − αnow)/α < 1.2 × 10−7 and .
... Equations (7) and (9) predict that at the present timė ...
... A much more stringent bound comes from the Oklo reactor, a natural nuclear reactor which was triggered about 1.8 billion years ago. From an analysis of this phenomenon, the authors of [9] obtained a bound ...
... On the one hand, changes in the QCD scale should be tightly constrained by big bang nucleosynthesis. But on the other hand changing the QCD scale may well modify the analysis [9] of the Oklo reactor data, which implicitly assumed that the QCD scale was constant. ...
Banks has proposed a relation between the scale of supersymmetry breaking and the cosmological constant in de Sitter space. His proposal has a natural extension to a general FRW cosmology, in which the supersymmetry breaking scale is related to the Hubble parameter. We study one consequence of such a relation, namely that coupling constants change as the universe evolves. We find that the most straightforward extension of Banks' proposal is disfavored by experimental bounds on variation of the fine structure constant.
... More uncertain is the translation of this bound on the energy variation into a bound on the variation of the fine-structure constant and other parameters: this passage requires strong assumptions about what is going to contribute to the atomic energies. This analysis was carried out in ref. [97], basically on the hypothesis that the main contribution to the resonance energy comes from the Coulomb potential of the electric interaction among the various protons of which the nucleus of Samarium consists. According to [97], after a certain amount of reasonable approximations, the energy bound translates into a bound on the variation of the electromagnetic coupling. ...
... This analysis was carried out in ref. [97], basically on the hypothesis that the main contribution to the resonance energy comes from the Coulomb potential of the electric interaction among the various protons of which the nucleus of Samarium consists. According to [97], after a certain amount of reasonable approximations, the energy bound translates into a bound on the variation of the electromagnetic coupling. A simple look at expression 4.2.11 ...
... This bound seems therefore to rule out our theoretical framework. However, things are not so simple: the derivation of a bound on a coupling out of a bound on energies works much differently in our framework, and we cannot simply use for our purpose the results of [97]. Indeed, in our framework what varies with time is not only the fine-structure constant, but also the nuclear force, and the proton and neutron mass as well. ...
Information is what tells us about the world. Could we think of physical reality itself as consisting just of information? Could the universe represent over the time the most general collection of logical codes? If we think of information as expressed in terms of binary codes, we could interpret binary sets as spatial arrangements of energy, giving rise to discrete geometries. Can we then identify a path through geometries, or sets of geometries, representing the history of the physical universe? This book introduces a theoretical framework that, by giving an answer to these questions, unifies general relativity and quantum mechanics at a more fundamental level. The geometry of the universe, its relativistic and quantum mechanical nature and the spectrum of elementary particles show up as the consequence of an entropic principle. All the masses and interaction couplings are computed as functions of the only free parameter, the age of the universe. This approach contributes to shed new light on several branches of physics, from elementary particle physics to the physics of high temperature superconductors, to cosmology, as well as on certain aspects of the natural evolution. This book updates the 2019 upload with the same name.
... Physicists have long speculated (at least since the time of P. A. M. Dirac [1]) about possible variations of the fundamental physical constants. The fine structure constant, α = e 2 /4π, is especially interesting to test, being dimensionless and accurately known experimentally. 1 Several attempts to constraint the time variation of α have been made in the last years [3,4,5,6]. The methods involved in these computations are quite different and the results are complementary since these calculations limit the variations of α at different cosmological times. ...
... Astrophysical observations of spectra of high red-shift quasar absorption lines have given limits of |∆α/α| ∼ < 10 −6 − 10 −4 for z ranging from 0.25 to 3 [5]. The geological limit from the Oklo natural nuclear reactor is about |∆α/α| ∼ < 10 −7 over a period of 1.8 billion years [6]. Recently, it was argued that from future observations of fluctuations in the cosmic microwave background radiation, variations of α could be bound by |∆α/α| ∼ < 10 −3 − 10 −2 for z ∼ 10 3 [10]. ...
We put bounds on the variation of the value of the fine structure constant , at the time of Big Bang nucleosynthesis. We study carefully all light elements up to Li. We correct a previous upper limit on estimated from He primordial abundance and we find interesting new potential limits (depending on the value of the baryon-to-photon ratio) from Li, whose production is governed to a large extent by Coulomb barriers. The presently unclear observational situation concerning the primordial abundances preclude a better limit than |\Delta \alpha/\alpha| \lsim 2\cdot 10^{-2}, two orders of magnitude less restrictive than previous bounds. In fact, each of the (mutually exclusive) scenarios of standard Big Bang nucleosynthesis proposed, one based on a high value of the measured deuterium primordial abundance and one based on a low value, may describe some aspects of data better if a change in of this magnitude is assumed.
... Although these provide the greatest sensitivity to the local rate of α variation, cosmologically they are of limited value because they only bound ∆α/α = (α(z) − α 0 )/α 0 , where α 0 is the value today, over a timescale of a few years at most. The 1.8 billion year old natural nuclear reactor at the Oklo uranium mine in Gabon is also extremely sensitive to the value of α at that time [16] because of the need to preserve a special resonant energy level for neutron capture, but the sensitivity is complicated by the ambient conditions when the reactor operated [17], sensitivity of the key nuclear resonance level to other coupling constants [18], and a best fit to the data that is doubled valued for the past value of α -one of those value ranges includes a small variation around a null variation but the other solution does not [19]. At far earlier times one can derive weaker bounds on ∆α/α from the physics of the cosmic microwave background [20] and big bang nucleosynthesis [21]. ...
... Firstly, with zero potential (V = 0), it is clear from (17) that the influence of the scalar field on cosmological dynamics is to increase the expansion rate: there is no question of the φ field causing collapse. Similarly, (18) shows that it cannot cause the universe to accelerate, and so cannot be a source of early inflation or late-time accelerated expansion of the universe. Obviously these conclusions may be changed by the addition of a potential. ...
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 FRW cosmology of this model in the cases of zero and non-zero spatial curvature is studied in detail, using dynamical systems techniques, for a wide class of potentials and coupling functions. All the asymptotic behaviours 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 non-relativistic matter. In particular, we investigate the cases where the scalar field driving alpha variations has exponential and power-law self-interaction potentials and the behaviour of theories where the coupling constant between matter and alpha variations is no longer a constant.
... (A) Oklo bound. Authors of [54] improved the result of an earlier work on the cosmological bound of α time variation, and they conclude a bound, | δα α | < O(10 −7 ). Arguments for this constraint are based on the natural Oklo reactor that happened ∼ 1.8 billion years ago, which is claimed to be sensitive to neutron capture cross section for Sm 149 (n, γ)Sm 150 proceeding via resonance formation. ...
... Actually, arguments for the bound given in [54] are rather intricate. A small resonance energy of order 100 meV arises from a nearly complete cancellation of Coulomb and strong interactions of protons inside Sm nuclei. ...
Cosmological analysis of extended Jordan-Brans-Dicke (eJBD) gravity is presented in the Einstein metric frame in which gravitational interaction is readily understandable. Our formulation is the first systematic investigation of how to introduce lagrangian of standard particle physics in eJBD framework consistently with the general principle of spontaneously broken gauge symmetry, which makes it possible to confront eJBD-based cosmology with observational and laboratory bounds on time variation of parameters, masses, and coupling constants, caused by time evolution of eJBD fields. Decomposition of standard particle physics lagrangian into independent gauge invariant pieces is proposed to avoid serious conflict that may arise from standard lagrangian transformed from the Jordan frame. Independent conformal factors are assigned to each of five gauge invariant pieces. The formulation is most unambiguously made possible by defining fields having canonical kinetic terms that allow us to use the canonical quantization rule of field theory. This construction gives as one of its consequences the canonical eJBD field χ that couples to the universal fermion current, a linear combination of baryon and lepton number currents, ∂ μχ (3 j μ B + j μ L ), in addition to the conventional trace of the energy-momentum tensor. Field equation of eJBD field along with gravitational equation is analyzed by using a simplified polynomial class of potential and conformal functions, giving time evolution of radiation, matter and dark energy densities consistent with observations when an appropriate set of model parameters are used. Finite temperature corrections are further calculated to give temperature dependent terms in eJBD field potential.
... At Oklo, the disappearance of isotopes with near-zero neutron resonance energy, most notably 149 Sm, can be used to constrain the shift in the lowest resonance, δE. The strongest limit on this energy shift is jδEj < 0.02 eV [38]. From Ref. [19], the variation of the resonance position is given by ...
... In this work, we examined variation in strange and charm quark masses. We obtained our strongest limits on the rate of mass variation, ð1=mÞðdm=dtÞ ≲ 10 −20 yr −1 , using measurements from the Oklo natural nuclear reactor in Ref. [38]. Assuming an expected accuracy of δω ∼ 10 −19 [47], we show that a 229 Th nuclear clock is expected to provide the best limits of ð1=mÞðdm=dtÞ ≲ 10 −22 yr −1 . ...
Spacetime variation of fundamental physical constants in an expanding Universe is predicted by a number of popular models. The masses of second-generation quarks are larger than first-generation quark masses by several orders of magnitude; therefore, spacetime variation in quark masses may significantly vary between each generation. We evaluate limits on variation in the s and c quark masses from big bang nucleosynthesis, Oklo natural nuclear reactor, Yb+, Cs, and Rb clock data. The construction of a Th229 nuclear clock is expected to enhance these limits by several orders of magnitude. Furthermore, constraints are obtained on an oscillating scalar or pseudoscalar cold dark matter field, as interactions of the field with quarks produce variations in quark masses.
... At Oklo, the disappearance of isotopes with near-zero neutron resonance energy, most notably 149 Sm, can be used to constrain the shift in the lowest resonance, δE. The strongest limit on this energy shift is |δE| < 0.02 eV [33]. From Ref. [17], the variation of the resonance position is given by ...
... In this work, we examined variation in strange and charm quark masses. We obtained our strongest limits on the rate of mass variation, (1/m)(dm/dt) < ∼ 10 −20 yr −1 , using measurements from the Oklo natural nuclear reactor in Ref. [33]. Assuming an expected accuracy of δω ∼ 10 −19 [42], we show that a 229 Th nuclear clock is expected to provide the best limits of (1/m)(dm/dt) < ∼ 10 −22 yr −1 . ...
Space-time variation of fundamental physical constants in expanding Universe is predicted by a number of popular models. The masses of second generation quarks are larger than first generation quark masses by several orders of magnitude, therefore space-time variation in quark masses may significantly vary between each generation. We evaluate limits on variation in the s and c quark masses from Big Bang nucleosynthesis, Oklo natural nuclear reactor, Yb+, Cs and Rb clock data. The construction of 229Th nuclear clock is expected to enhance these limits by several orders of magnitude. Furthermore, constraints are obtained on an oscillating scalar or pseudoscalar cold dark matter field, as interactions of the field with quarks produce variations in quark masses.
... Laboratory atomic clock comparisons have achieved remarkable precision of ∼ 10 −17 per year in probing variations at human timescales (Prestage et al. 1995;Rosenband et al. 2008). Extending to geological timescales, studies of the Oklo natural nuclear reactor provide constraints reaching back approximately 2 Gyr into cosmic history (Shlyakhter 1976;Damour & Dyson 1996). ...
The quantum nature of gravity remains one of the greatest mysteries of modern physics, with many unified theories predicting variations in fundamental constants across space and time. Here we present precise measurements of these variations at galactic dynamical timescales - a critical but previously unexplored regime. Using simultaneous observations of H \textsc{i} and OH lines in M31, we probe potential variations of fundamental constants at a lookback time of 2.5 million years. We obtained , with complementary constraints on , and , where is the fine structure constant, is the proton-electron mass ratio, and is the proton g-factor. These results bridge the gap between laboratory tests and cosmological observations, providing unique insights into the coupling between local dynamics and fundamental physics. Our findings challenge theories predicting significant variations over galactic timescales, while demonstrating a powerful new probe of quantum gravity models.
... ± 0.8) × 10 −17 /yr. This limit was derived in [11] under the assumption that other parameters, especially those related to the nuclear physics, did not change during the last 2 billion years. It was recently pointed out [7,10], that this limit must be reconsidered if a time change of nuclear physics parameters is taken into account. ...
Astrophysical indications that the fine structure constant has undergone a small time variation during the cosmological evolution are discussed within the framework of the standard model of the electroweak and strong interactions and of grand unification. A variation of the electromagnetic coupling constant could either be generated by a corresponding time variation of the unified coupling constant or by a time variation of the unification scale, of by both. The various possibilities, differing substantially in their implications for the variation of low energy physics parameters like the nuclear mass scale, are discussed. The case in which the variation is caused by a time variation of the unification scale is of special interest. It is supported in addition by recent hints towards a time change of the proton-electron mass ratio.
... Such tests interestingly complement experimental tests of the Local Lorentz Invariance and of the Universality of free-fall to experimentally establish the validity of Einstein's Equivalence Principle (EEP). They also complement tests of the variability of fundamental constants on different timescales, geological timescale [20,21] and cosmological timescale [22,23]. Nearly all unification theories (in particular string theories) violate EEP at some level [24,25,26] which strongly motivates experimental searches for such violations. ...
This paper describes advances in microwave frequency standards using laser-cooled atoms at BNM-SYRTE. First, recent improvements of the Cs and Rb atomic fountains are described. Thanks to the routine use of a cryogenic sapphire oscillator as an ultra-stable local frequency reference, a fountain frequency instability of where is the measurement time in seconds is measured. The second advance is a powerful method to control the frequency shift due to cold collisions. These two advances lead to a frequency stability of at 7\times 10^{-16}^{87}^{133}$Cs fountains. Finally we give an update on the cold atom space clock PHARAO developed in collaboration with CNES. This clock is one of the main instruments of the ACES/ESA mission which is scheduled to fly on board the International Space Station in 2008, enabling a new generation of relativity tests.
... From the radioactive life-time of 187 Re derived from meteoritic studies [9], the constraint is given by |∆α/α| ∼ < 10 −7 for redshift z = 0.45. Finally, from the Oklo natural nuclear reactor [10], it is found that |∆α/α| ∼ < 10 −7 for redshift z = 0.14. For convenience, we summarize the above constraints in Table I A varying α might be due to a varying speed of light c [11,12,13], while Lorentz invariance is broken. ...
Since about ten years ago, varying theories attracted many attentions, mainly due to the first observational evidence from the quasar absorption spectra that the fine structure ``constant'' might change with cosmological time. In this work, we investigate the cosmic evolution of driven by the Dirac-Born-Infeld (DBI) scalar field. To be general, we consider various couplings between the DBI scalar field and the electromagnetic field. We also confront the resulting with the observational constraints, and find that various cosmological evolution histories of are allowed. Comparing with the case of varying driven by quintessence, the corresponding constraints on the parameters of coupling have been relaxed, thanks to the relativistic correction of the DBI scalar field.
... But if true, it must mean that at least one of the three fundamental constants that constitute α must vary. The possibility that some constants of Nature could vary in space-time has remained a subject of fascination which has motivated numerous theoretical and experimental researches [10,23]. ...
We will study rigorously the notion of mixed states and their density operators (or matrices.) We will also discuss the quantum-mechanical consequences of possible variations of Planck's constant h. This Review has been written having in mind two readerships: mathematical physicists and quantum physicists. The mathematical rigor is maximal, but the language and notation we use throughout should be familiar to physicists.
... Recent experimental evidence that the fine structure constant may be drifting 3,4 and has triggered much interest in theories that account for the drift in fundamental constants [5][6][7][8][9][10] . Also, it has provided stimulus to laboratory tests, which aim to improve the precision of measurements of the constancy of the fine structure constant [11][12][13] . Furthermore, it is well established that the fine structure constant varies with energy (or distance) as one probes close to the electron 14 . ...
The fine structure constant, alpha, is shown to be proportional to the ratio of the quanta of electric and magnetic flux of force of the electron, and provides a new representation, which is global across all unit systems. Consequently, a variation in alpha was shown to manifest due to a differential change in the fraction of the quanta of electric and magnetic flux of force, while a variation in hcross.c was shown to manifest due to the common mode change. The representation is discussed with respect to the running of the fine structure constant at high energies (small distances), and a putative temporal drift. It is shown that the running of the fine structure constant is due to equal components of electric screening (polarization of vacuum) and magnetic anti-screening (magnetization of vacuum), which cause the perceived quanta of electric charge to increase at small distances, while the magnetic flux quanta decreases. This introduces the concept of the bare magnetic flux quanta as well as the bare electric charge. With regards to temporal drift, it is confirmed that it is impossible to determine which fundamental constant is varying if alpha varies.
... The variability of physical "constants" is a possibility that cannot be outruled and which has being an active area of research for some time in cosmology and astrophysics. In fact, since Paul Dirac [1,2] suggested in 1937 the "Large Numbers Hypothesis" that some constants of Nature could vary in space and time, the topic has remained a subject of fascination which has motivated numerous theoretical and experimental researches [3,4]. ...
Recent cosmological measurements tend to confirm that the fine structure constant {\alpha} is not immutable and has undergone a tiny variation since the Big Bang. Choosing adequate units, this could also reflect a variation of Planck's constant h. The aim of this Letter is to explore some consequences of such a possible change of h for the pure and mixed states of quantum mechanics. Surprisingly enough it is found that not only is the purity of a state extremely sensitive to such changes, but that quantum states can evolve into classical states, and vice versa. A complete classification of such transitions is however not possible for the moment being because of yet unsolved mathematical difficulties related to the study of positivity properties of trace class operators.
... Simultaneous agreement with the more restrictive bounds on the total change |∆α/α| < 10 −7 from z ≈ 0.14 to the present from the Oklo natural fission reactor 1.8 Gyrs ago [4,5] (by analyzing isotopic ratios of Sm) and |∆α/α| < 3 × 10 −7 from z ≈ 0.44 to the present from samples of meteorites formed in the early solar system 4.6 Gyrs ago [6] (by analyzing the ratio of 187 Re to 187 Os) can be achieved if the mass of the scalar field is on the order of 0.5-0.6 Ω ...
Cosmological variation of the fine structure constant due to the evolution of a spatially homogeneous ultra-light scalar field () during the matter and dominated eras is analyzed. Agreement of with the value suggested by recent observations of quasar absorption lines is obtained by adjusting a single parameter, the coupling of the scalar field to matter. Asymptotically in this model goes to a constant value in the early radiation and the late dominated eras. The coupling of the scalar field to (nonrelativistic) matter drives slightly away from in the epochs when the density of matter is important. Simultaneous agreement with the more restrictive bounds on the variation from the Oklo natural fission reactor and from meteorite samples can be achieved if the mass of the scalar field is on the order of 0.5--0.6 , where . Depending on the scalar field mass, may be slightly smaller or larger than at the times of big bang nucleosynthesis, the emission of the cosmic microwave background, the formation of early solar system meteorites, and the Oklo reactor. The effects on the evolution of due to nonzero mass for the scalar field are emphasized. An order of magnitude improvement in the laboratory technique could lead to a detection of .
... These constraints can be divided into two main groups: local and astro-cosmological. The local constraints derive from experiments in our local bound gravitational system: the Oklo natural reactor (z = 0.14), where ∆α α ≤ 10 −7 (Fujii et al 2000;Damour & Dyson 1996;Fujii 2003;Shlyakhter 2003). However, the use of an equilibrium neutron spectrum in this analyses has recently been criticised by (Lamoreaux 2003). ...
Using the BSBM varying-alpha theory, with dark matter dominated by magnetic energy, and the spherical collapse model for cosmological structure formation, we have studied the effects of the dark-energy equation of state and the coupling of alpha to the matter fields on the space and time evolution of alpha. We have compared its evolution inside virialised overdensities with that in the cosmological background, using the standard () CDM model of structure formation and the dark-energy modification, wCDM. We find that, independently of the model of structure formation one considers, there is always a difference between the value of alpha in an overdensity and in the background. In a SCDM model, this difference is the same, independent of the virialisation redshift of the overdense region. In the case of a wCDM model, especially at low redshifts, the difference depends on the time when virialisation occurs and the equation of state of the dark energy. At high redshifts, when the wCDM model becomes asymptotically equivalent to the SCDM one, the difference is constant. At low redshifts, when dark energy starts to dominate the cosmological expansion, the difference between alpha in a cluster and in the background grows. The inclusion of the effects of inhomogeneity leads naturally to no observable local time variations of alpha on Earth and in our Galaxy even though time variations can be significant on quasar scales. The inclusion of the effects of inhomogeneous cosmological evolution are necessary if terrestrial and solar-system bounds on the time variation of the fine structure 'constant' are to be correctly compared with extragalactic data.
... The best results concern the electromagnetic coupling, i.e. the fine-structure constant α em . A recent reanalysis of the Oklo phenomenon gives a conservative upper bound [4] ...
The confrontation between Einstein's gravitation theory and experimental results, notably binary pulsar data, is summarized and its significance discussed. Experiment and theory agree at the 10^{-3} level or better. All the basic structures of Einstein's theory (coupling of gravity to matter; propagation and self-interaction of the gravitational field, including in strong-field conditions) have been verified. However, the theoretical possibility that scalar couplings be naturally driven toward zero by the cosmological expansion suggests that the present agreement between Einstein's theory and experiment might be compatible with the existence of a long-range scalar contribution to gravity (such as the dilaton field, or a moduli field, of string theory). This provides a new theoretical paradigm, and new motivations for improving the experimental tests of gravity.
... To date, very stringent tests exist on geological and cosmological timescales. The analysis of the Oklo nuclear reactor showed that, 2 × 10 9 years ago, α did not differ from the present value by more than 10 −7 of its value [6]. Light emitted by distant quasars has been used to perform absorption spectroscopy of interstellar clouds. ...
Over five years we have compared the hyperfine frequencies of 133Cs and 87Rb atoms in their electronic ground state using several laser cooled 133Cs and 87Rb atomic fountains with an accuracy of ~10^{-15}. These measurements set a stringent upper bound to a possible fractional time variation of the ratio between the two frequencies : (d/dt)ln(nu_Rb/nu_Cs)=(0.2 +/- 7.0)*10^{-16} yr^{-1} (1 sigma uncertainty). The same limit applies to a possible variation of the quantity (mu_Rb/mu_Cs)*alpha^{-0.44}, which involves the ratio of nuclear magnetic moments and the fine structure constant.
... Most results are consistent with no significant variation in α. Furthermore, local methods have also been employed to obtain stringent bounds on potential variations in α, such as studies of the Oklo natural nuclear reactor [67][68][69][70] and laboratory measurements of atomic clocks with different atomic numbers [71][72][73]. In addition to its significant impact on fundamental physics, this possibility has recently been suggested as a potential solution to some cosmological challenges, such as the Hubble tension [44,[74][75][76][77][78]. ...
Testing possible variations in fundamental constants of nature is a crucial endeavor in observational cosmology. This paper investigates potential cosmological variations in the fine structure constant () through a non-parametric approach, using galaxy cluster observations as the primary cosmological probe. We employ two methodologies based on galaxy cluster gas mass fraction measurements derived from X-ray and Sunyaev-Zeldovich observations, along with luminosity distances from type Ia supernovae. We also explore how different values of the Hubble constant () impact the variation of across cosmic history. When using the Planck satellite's observations, a constant is ruled out at approximately the 3 confidence level for . Conversely, employing local estimates of restores agreement with a constant .
... Most results are consistent with no significant variation in α. Furthermore, local methods have also been employed to obtain stringent bounds on potential variations in α, such as studies of the Oklo natural nuclear reactor [67][68][69][70] and laboratory measurements of atomic clocks with different atomic numbers [71][72][73]. In addition to its significant impact on fundamental physics, this possibility has recently been suggested as a potential solution to some cosmological challenges, such as the Hubble tension [44,[74][75][76][77][78]. ...
Testing possible variations in fundamental constants of nature is a crucial endeavor in observational cosmology. This paper investigates potential cosmological variations in the fine structure constant ( α ) through a non-parametric approach, using galaxy cluster observations as the primary cosmological probe. We employ two methodologies based on galaxy cluster gas mass fraction measurements derived from X-ray and Sunyaev–Zeldovich observations, along with luminosity distances from type Ia supernovae. We also explore how different values of the Hubble constant ( H 0 ) impact the variation of α across cosmic history. When using the Planck satellite’s H 0 observations, a constant α is ruled out at approximately the 3 σ confidence level for z ≲ 0.5 . Conversely, employing local estimates of H 0 restores agreement with a constant α .
... Probing the variation of α has a long history (e.g., Savedoff 1956;Bahcall & Schmidt 1967). It is now clear that any relative α variation Δα/α in the local Universe or time variation a a ( / a a º d dt) at the present time, if it exists, must be extremely small (e.g., Damour & Dyson 1996;Petrov et al. 2006;Rosenband et al. 2008;Murphy et al. 2022). Therefore, astrophysical observations mostly focus on highredshift objects and explore the α variation at early times when a variable α is theoretically more possible (e.g., Barrow et al. 2002;Alves et al. 2018). ...
We present strong constraints on the spacetime variation of the fine-structure constant α using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize ∼110,000 galaxies with strong and narrow [O iii ] λ λ 4959, 5007 emission lines to measure the relative variation Δ α / α in space and time. The [O iii ] doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our galaxy sample spans a redshift range of 0 < z < 0.95, covering half of all cosmic time. We divide the sample into subsamples in 10 redshift bins (Δ z = 0.1), and calculate Δ α / α for the individual subsamples. The uncertainties of the measured Δ α / α are roughly between 2 × 10 ⁻⁶ and 2 × 10 ⁻⁵ . We find an apparent α variation with redshift at a level of Δ α / α = (2–3) × 10 ⁻⁵ . This is highly likely to be caused by systematics associated with wavelength calibration, since such small systematics can be caused by a wavelength distortion of 0.002–0.003 Å, which is beyond the accuracy that the current DESI data can achieve. We refine the wavelength calibration using sky lines for a small fraction of the galaxies, but this does not change our main results. We further probe the spatial variation of α in small redshift ranges, and do not find obvious, large-scale structures in the spatial distribution of Δ α / α . As DESI is ongoing, we will include more galaxies, and by improving the wavelength calibration, we expect to obtain a better constraint that is comparable to the strongest current constraint.
... In particular, astrophysical observations are able to constrain the α variation in the distant Universe. Previous studies have shown that any relative α variation ∆α/α or time variationα/α (α ≡ dα/dt), if it exists, must be extremely small (e.g., Damour & Dyson 1996;Petrov et al. 2006;Rosenband et al. 2008;Murphy et al. 2022). ...
We present constraints on the spacetime variation of the fine-structure constant at redshifts using JWST emission-line galaxies. The galaxy sample consists of 572 high-quality spectra with strong and narrow [O III] 4959,5007 doublet emission lines from 522 galaxies, including 267 spectra at . The [O III] doublet lines are arguably the best emission lines to probe the variation in . We divide our sample into 5 subsamples based on redshift and calculate the relative variation for the individual subsamples. The calculated values are consistent with zero within at all redshifts, suggesting no time variation in above a level of () in the past 13.2 billion years. When the whole sample is combined, the constraint is improved to be . We further test the spatial variation in using four subsamples of galaxies in four different directions on the sky. The measured values are consistent with zero at a level of . While the constraints in this work are not as stringent as those from lower-redshift quasar absorption lines in previous studies, this work uses an independent tracer and provides the first constraints on at the highest redshifts. Our analyses also indicate that the relative wavelength calibration of the JWST spectra is robust. With the growing number of emission-line galaxies from JWST, we expect to achieve stronger constraints in the future.
... This enormous cross-section arises because of a resonance state just above zero to which Sm 149 can be excited by the capture of a free neutron. It was shown in Ref. 45 that a value of em = em larger than 10 À7 shifts the resonance energy level, and thus the neutron capture crosssection, far too much to be compatible with the observed Sm 149 abundance. We show the resulting constraints in Fig. 3. ...
The principles of time and space translation invariance, which result in energy and momentum conservation, are among the most fundamental and widely accepted symmetry assumptions in physics. However, it is judicious to subject such assumptions to experimental and observational scrutiny. Thus, we initiate this process by specifying a simple periodic time dependence that contravenes time translation invariance in QED, and establishing phenomenological constraints on it. Besides observational and experimental constraints on time-varying couplings, we emphasise probes of energy conservation violation such as spontaneous photon and electron pair production and the e→eγ process.
... This enormous cross-section arises because of a resonance state just above zero to which Sm 149 can be excited by the capture of a free neutron. It was shown in ref. [61] that a value of δα em /α em larger than 10 −7 shifts the resonance energy level, and thus the neutron capture cross-section, far too much to be compatible with the observed Sm 149 abundance. We show the resulting constraints in figure 3. ...
A bstract
Time and space translation invariance, giving rise to energy and momentum conservation, are not only amongst the most fundamental but also the most generally accepted symmetry assumptions in physics. It is nevertheless prudent to put such assumptions to experimental and observational tests. In this note, we take the first step in this direction, specifying a simple periodic time dependence that violates time translation invariance in QED, and setting phenomenological constraints on it. In addition to observational and experimental constraints on time varying couplings, we focus on probes of violation of energy conservation such as spontaneous production of photon and electron pairs and the e → eγ process. We discuss similarities and differences to the discussion of time varying fundamental constants and to the case of a light bosonic dark matter field that usually also causes oscillating effects.
... This enormous cross-section arises because of a resonance state just above zero to which Sm 149 can be excited by the capture of a free neutron. It was shown in Ref. [58] that a value of δα em /α em larger than 10 −7 shifts the resonance energy level, and thus the neutron capture cross-section, far too much to be compatible with the observed Sm 149 abundance. We show the resulting constraints in Fig. 3. ...
Time and space translation invariance, giving rise to energy and momentum conservation, are not only amongst the most fundamental but also the most generally accepted symmetry assumptions in physics. It is nevertheless prudent to put such assumptions to experimental and observational tests. In this note, we take the first step in this direction, specifying a simple periodic time dependence that violates time translation invariance in QED, and setting phenomenological constraints on it. In addition to observational and experimental constraints on time varying couplings, we focus on probes of violation of energy conservation such as spontaneous production of photon and electron pairs and the process. We discuss similarities and differences to the discussion of time varying fundamental constants and to the case of a light bosonic dark matter field that usually also causes oscillating effects.
... The uncertainties decrease slightly than previous works which modify the fine-structure constant at only the recombination epoch. For example, the Planck Collaboration released ∆α/α EM = (3.6 ± 3.7) × 10 −3 at 68% C.L. [12] and ref. [13] obtained α/α EM = 0.9993 ± 0.0025 at 68% C.L.. Comparing other measurements from astrophysics, our constraints are tighter than ∆α/α EM < 10 −2 − 10 −3 from the abundance of light elements during BBN [47], but weaker than constraints of ∆α/α EM ∼ 10 −7 −10 −8 from the 1.8 billion-year-old natural nuclear reactor at the Oklo Uranium Mine in Gabon [48], ∆α/α EM ∼ 10 −5 −10 −6 from the spectral lines of quasars [49][50][51] and so on [16]. However, in the ΛCDM+α rec /α EM + α rei /α EM model, our results show α rec /α EM = 1.001494 +0.002041 −0.002063 and α rei /α EM = 0.8540342 +0.031678 −0.027209 at 68%C.L.. ...
In cosmology, the fine-structure constant can affect the whole ionization history. However, the previous works confine themselves to the recombination epoch and give various strong constraints on the fine-structure constant. In this paper, we also take the reionization epoch into consideration and do a consistency test of the fine-structure constant from the whole ionization history. From the data combination of Planck 2018, BAO data, SNIa samples, SFR density from UV and IR measurements, and the Q HII constraints, we find the constraint on the fine-structure constant during the recombination epoch is α rec / α EM = 1.001494 +0.002041 -0.002063 and its counterpart during the reionization epoch is α rei / α EM = 0.854034 +0.031678 0.027209 at 68% C.L.. They are not consistent with each other by 4.64 σ . A conservative explanation for such a discrepancy is that there are some issues in the data we used. We prefer a calibration of some important parameters involved in reconstructing the reionization history.
... On the other hand, laboratory experiments, mostly based on high-resolution spectroscopy and atomic clocks, only test for present-day variations on a few-years scale, but can reach extremely high accuracies. Starting with geological methods, analysis of products of radioactive decay in the Oklo natural fission reactor was used in one of the very first studies constraining the variation of α [59], later refined in [60]- [63]. However, the derived constraints are not considered to be fully reliable, and deeper analysis of these results is needed [55]. ...
The hydrogen molecular ions H2+ and HD+ are promising systems for the metrology of fundamental constants. A Doppler-free two-photon vibrational transition in HD+ was recently measured at Amsterdam VU with an uncertainty of about 3 parts per trillion (ppt), whereas QED theoretical predictions have reached uncertainties of 7-8 ppt. In order to determine the transition frequencies from experimental spectra, various systematic effects have to be considered. In the first part of this thesis, I calculated one of the main systematic effects, namely the AC Stark shift induced by the different lasers used in the experiment. A spin-averaged transition frequency was then deduced from the measured hyperfine components, and compared with theoretical predictions, which allowed an improved determination of the proton-electron ratio with an uncertainty of 21 ppt. This required an improved theoretical description of the hyperfine structure, which is the object of the second part of the thesis. The theoretical accuracy was limited by the spin-orbit and spin-spin tensor interactions. The calculation of higher-order relativistic corrections to these interaction terms, following the NRQED approach, is presented in detail. Improved theoretical values of the spin-orbit and spin-spin tensor interaction coeffcients are obtained and compared with available experimental data. Very good agreement is observed in the case of H2+, whereas some yet unexplained discrepancies are observed in HD+.
... The most stringent bound on linear drifts in α at redshifts z 0.5 comes from optical clock comparison measurements with Yb + and is at the level |d ln(α)/dt| 10 -18 yr -1 [20]. This bound is one and two orders of magnitude, respectively, more stringent than bounds pertaining to the Oklo phenomenon [154][155][156][157] and meteorite dating [158]; see Table 1 for a summary of the bounds. The bounds from two optical clock measurements separated in time can be improved with longer time intervals between the measurements. ...
The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models.
... The most stringent bound on linear drifts in α at redshifts z 0.5 comes from optical clock comparison measurements with Yb + and is at the level |d ln(α)/dt| 10 −18 yr −1 [20]. This bound is one and two orders of magnitude, respectively, more stringent than bounds pertaining to the Oklo phenomenon [151][152][153][154] and meteorite dating [155]; see Table 1 for a summary of the bounds. The bounds from two optical clock measurements separated in time can be improved with longer time intervals between the measurements. ...
The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models.
... The Planck Collaboration (2015) obtained Δα/α ≈ 10 −3 at a redshift of z ≈ 10 3 by analyzing the CMB spectra, and the constraints given by the abundance of the light elements emerged during BBN are not very tight (approximately Δα/α <10 −2 -10 −3 at z ≈ 10 9 -10 10 ), too (Mosquera & Civitarese 2013). The 1.8 billionyear-old natural nuclear reactor at the Oklo Uranium Mine in Gabon can give much tighter bounds on the time variations of α (Δα/α ≈ 10 −7 -10 −8 ; Damour & Dyson 1996;Lamoreaux & Torgerson 2004). The most sensitive constraints on Δα/α were achieved at z ≈ 1−6 from the spectral lines significantly affected by relativistic effects in absorbing clouds around distant quasars. ...
We explore a possible time variation of the fine structure constant ( α ≡ e ² / ℏ c ) using the Sunyaev–Zel’dovich effect measurements of galaxy clusters along with their X-ray observations. Specifically, the ratio of the integrated Comptonization parameter Y SZ D A 2 and its X-ray counterpart Y X is used as an observable to constrain the bounds on the variation of α . Considering the violation of the cosmic distance duality relation, this ratio depends on the fine structure constant of ∼ α ³ . We use the quintessence model to provide the origin of α time variation. In order to give a robust test on α variation, two galaxy cluster samples, the 61 clusters provided by the Planck collaboration and the 58 clusters detected by the South Pole Telescope (SPT), are collected for analysis. Their X-ray observations are given by the XMM-Newton survey. Our results give ζ = − 0.203 − 0.099 + 0.101 for the Planck sample and ζ = − 0.043 − 0.148 + 0.165 for the SPT sample, indicating that α is constant with redshift within 3 σ and 1 σ for the two samples, respectively.
... Some observational measurements have also been considered to investigate a possible variation of the fine-structure constant (in electrostatic cgs units α = e 2 /hc, where e is the elementary charge,h the reduced Planck's constant, and c the speed of the light). The absorption spectra of quasars, for instance, have been much used to explore a possible cosmological time variation of α [11][12][13][14][15][16][17], and also by the rare-earth element abundance data from Oklo [18]. Very recently, from 4 quasars spectral observations up to z ≈ 7.1, no evidence for a temporal change has been found. ...
In order to probe a possible time variation of the fine-structure constant ( α ), we propose a new method based on Strong Gravitational Lensing and Type Ia Supernovae observations. By considering a class of runaway dilaton models, where Δ α α = - γ ln ( 1 + z ) , we obtain constraints on Δ α α at the level γ ∼ 10 - 2 ( γ captures the physical properties of the model). Since the data set covers the redshift range 0.075 ≤ z ≤ 2.2649 , the constraints derived here provide independent bounds on a possible time variation of α at low, intermediate and high redshifts.
... The Planck Collaboration obtained ∆α/α ≈ 10 −3 at redshift z ≈ 10 3 by analyzing the CMB spectra (PLANCK Collaboration 2015), and the constraints given by the abundance of the light elements emerged during BBN are not very tight (approximately ∆α/α < 10 −2 − 10 −3 at z ≈ 10 9 − 10 10 ), too (Mosquera & Civitarese 2013). The 1.8 billion-year-old natural nuclear reactor at the Oklo Uranium Mine in Gabon can give much tighter bounds on the time variations of α (∆α/α ≈ 10 −7 − 10 −8 ) (Damour & Dyson 1996;Lamoreaux & Torgerson 2004). The most sensitive constraints on ∆α/α were achieved at z ≈ 1 − 6 from the spectral lines significantly affected by relativistic effects in absorbing clouds around distant quasars. ...
We explore a possible time variation of the fine structure constant () using the Sunyaev-Zel'dovich effect measurements of galaxy clusters along with their X-ray observations. Specifically, the ratio of the integrated Compto-ionization parameter and its X-ray counterpart is used as an observable to constrain the bounds on the variation of . Considering the violation of cosmic distance duality relation, this ratio depends on the fine structure constant as . We use the quintessence model to provide the origin of time variation. In order to give a robust test on variation, two galaxy cluster samples, the 61 clusters provided by the Planck collaboration and the 58 clusters detected by the South Pole Telescope, are collected for analysis. Their X-ray observations are given by the XMM-Newton survey. Our results give for the Planck sample and for the SPT sample, indicating that is constant with redshift within and for the two samples, respectively.
... Therefore, a large number of searches for variations of α have been carried out using a plethora of astrophysical/cosmological probes such as CMB [19][20][21][22], Big-Bang Nucleosynthesis [23], supermassive black hole at the galactic center [24], white dwarf spectra [25], strong gravitational lensing [26], and also Earth-based measurements using the Oklo natural reactor [27], atomic clocks [28] etc. A recent review summarizing the latest results from all these searches can be found in Martins [3] and references therein. ...
We search for a variation of the electromagnetic fine structure constant () using a sample of 58 SZ selected clusters in the redshift range () detected by the South Pole Telescope, along with X-ray measurements using the XMM-Newton observatory. Following arXiv:1901.10947, we use the ratio of integrated Compto-ionization and its X-ray counterpart as our observable to search for a variation of . We search for a logarithmic dependence of as a function of redshift: , as predicted by runaway dilaton models. We find that = , which indicates that is constant with redshift within . We also search for a dipole variation of the fine structure constant using the same cluster sample. We do not find any evidence for such a spatial variation.
The quantum nature of gravity remains one of the greatest mysteries of modern physics, with many unified theories predicting variations in fundamental constants across space and time. Here we present precise measurements of these variations at galactic dynamical timescales—a critical but previously unexplored regime. Using simultaneous observations of H i and OH lines in M31, we probe potential variations of fundamental constants at a look-back time of 2.5 million yr. We obtained Δ ( μ α 2 g p 0.64 ) / ( μ α 2 g p 0.64 ) < 3.6 × 1 0 − 6 , with complementary constraints on Δ( μα ² )/( μα ² ) < 4.6 × 10 ⁻³ , and Δ g p / g p < 7.2 × 10 ⁻³ , where α is the fine structure constant, μ is the proton–electron mass ratio, and g p is the proton g -factor. These results bridge the gap between laboratory tests and cosmological observations, providing unique insights into the coupling between local dynamics and fundamental physics. Our findings challenge theories predicting significant variations over galactic timescales while demonstrating a powerful new probe of quantum gravity models.
We present constraints on the spacetime variation of the fine-structure constant α at redshifts 2.5 ≤ z < 9.5 using JWST emission-line galaxies (ELGs). The galaxy sample consists of 621 high-quality spectra with strong and narrow [O iii ] λλ 4959,5007 doublet emission lines from 578 galaxies, including 232 spectra at z > 5. The [O iii ] doublet lines are arguably the best emission lines to probe the variation in α . We divide our sample into six subsamples based on redshift and calculate the relative variation Δ α / α for the individual subsamples. The calculated Δ α / α values are consistent with zero within 1 σ at all redshifts, suggesting no time variation in α above a level of (1–2) × 10 ⁻⁴ (1 σ ) in the past 13.2 billion yr. When the whole sample is combined, the constraint is improved to be Δ α / α = (0.2 ± 0.7) × 10 ⁻⁴ . We further test the spatial variation in α using four subsamples of galaxies in four different directions on the sky. The measured Δ α / α values are consistent with zero at a 1 σ level of ∼2 × 10 ⁻⁴ . While the constraints in this work are not as stringent as those from lower-redshift quasar absorption lines in previous studies, this work uses an independent tracer and provides the first constraints on Δ α / α at the highest redshifts. With the growing number of ELGs from JWST, we expect to achieve stronger constraints in the future.
Recent experimental data indicates that the fine structure constant alpha may be varying on cosmological time scales. We consider the possibility that such a variation could be induced by a second order phase transition which occurs at late times (z ~ 1 - 3) and involves a change in the vacuum expectation value (vev) of a scalar with milli-eV mass. Such light scalars are natural in supersymmetric theories with low SUSY breaking scale. If the vev of this scalar contributes to masses of electrically charged fields, the low-energy value of alpha changes during the phase transition. The observational predictions of this scenario include isotope-dependent deviations from Newtonian gravity at sub-millimeter distances, and (if the phase transition is a sharp event on cosmological time scales) the presence of a well-defined step-like feature in the alpha(z) plot. The relation between the fractional changes in alpha and the QCD confinement scale is highly model dependent, and even in grand unified theories the change in alpha does not need to be accompanied by a large shift in nucleon masses.
We show that the Supernovae results, implying evidence for an accelerating Universe, may be closely related to the recent discovery of redshift dependence in the fine structure constant . The link is a class of varying speed of light (VSL) theories which contain cosmological solutions similar to quintessence. During the radiation dominated epoch the cosmological constant is prevented from dominating the Universe by the usual VSL mechanism. In the matter epoch the varying c effects switch off, allowing to eventually surface and lead to an accelerating Universe. By the time this happens the residual variations in c imply a changing at a rate that is in agreement with observations.
We review the experimental evidence for Einstein's special and general relativity. A variety of high precision null experiments verify the weak equivalence principle and local Lorentz invariance, while gravitational redshift and other clock experiments support local position invariance. Together these results confirm the Einstein Equivalence Principle which underlies the concept that gravitation is synonymous with spacetime geometry, and must be described by a metric theory. Solar system experiments that test the weak-field, post-Newtonian limit of metric theories strongly favor general relativity. The Binary Pulsar provides tests of gravitational-wave damping and of strong-field general relativity. Recently discovered binary pulsar systems may provide additional tests. Future and ongoing experiments, such as the Gravity Probe B Gyroscope Experiment, satellite tests of the Equivalence principle, and tests of gravity at short distance to look for extra spatial dimensions could constrain extensions of general relativity. Laser interferometric gravitational-wave observatories on Earth and in space may provide new tests of gravitational theory via detailed measurements of the properties of gravitational waves.
The possibility of variations of the values of fundamental constants is a phenomenon predicted by a number of scenarios beyond General Relativity. This can happen if “our” fundamental constants are not the actual constants of the fundamental theory and their value is instead determined, for example, by the background value of some new field or the size of extra dimensions. So far, most studies have been devoted to constrain possible temporal variations of the electromagnetic fine structure constant , the proton to electron mass ratio , and the gravitational constant . Apart some claims of the detection of a temporal or spatial variation of and , so far there is no clear observational evidence of any variation of our fundamental constants.
Astrophysical tests of the stability—or not—of fundamental couplings (e.g., can the numerical value ∼1/137 of the fine-structure constant α = e2/ℏc vary with astronomical time?) are a very active area of observational research. Using a specific α-free non-relativistic and nonlinear isotropic quantum model compatible with its quantum electrodynamics (QED) counterpart yields the 99% accurate solution α = 7.364 × 10−3 vs its experimental value 7.297 × 10−3. The ∼1% error is due to the deliberate use of mean-field Hartree approximation involving lowest-order QED in the calculations. The present theory has been checked by changing the geometry of the model. Moreover, it fits the mathematical solution of the original nonlinear integro-differential Hartree system by use of a rapidly convergent series of nonlinear eigenstates [G. Reinisch, Phys. Lett. A 498, 129347 (2024)]. These results strongly suggest the mathematical transcendental nature—e.g., like for π or e—of α’s numerical value of ∼1/137 and, hence, its astrophysical as well as its cosmological stability.
Bounds on the cosmological variation of the fine structure constant α inferred from Oklo neutron capture data are sometimes taken cum grano salis. It is possible to quantify uncertainties related to the treatment of excitation, deformation and the Coulomb interaction. On the basis of this analysis, it is concluded that Oklo data imply the relative change in α over the last 1.9 billion years is < 0.01 ppm (95% CL). Accommodation of this constraint represents a challenge to dark energy models that predict that fundamental constants do change.
Toward understanding of dark energy, we propose a novel method to directly produce a chameleon particle and force its decay under controlled gas pressure in a laboratory-based experiment. Chameleon gravity, characterized by its varying mass depending on its environment, could be a source of dark energy, which is predicted in modified gravity. A remarkable finding is a correspondence between the varying mass and a characteristic pressure dependence of a stimulated photon-photon scattering rate in a dilute gas surrounding a focused photon-beam spot. By observing a steep pressure dependence in the scattering rate, we can directly extract the characteristic feature of the chameleon mechanism. As a benchmark model of modified gravity consistent with the present cosmological observations, a reduced F(R) gravity is introduced in the laboratory scale. We then demonstrate that the proposed method indeed enables a wide-ranging parameter scan of such a chameleon model with the varying mass around (0.1−1) (μeV) by controlling pressure values.
We review properties of cosmological theories for the variation of the fine structure ‘constant’. 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. Properties of cosmological theories for the variation of the fine structure ‘constant’ are reviewed. Some general features of the cosmological models are highlighted 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.
We review the experimental evidence for Einstein's special and general relativity. A variety of high precision null experiments verify the weak equivalence principle and local Lorentz invariance, while gravitational redshift and other clock experiments support local position invariance. Together these results confirm the Einstein Equivalence Principle which underlies the concept that gravitation is synonymous with spacetime geometry, and must be described by a metric theory. Solar system experiments that test the weak‐field, post‐Newtonian limit of metric theories strongly favor general relativity. The Binary Pulsar provides tests of gravitational‐wave damping and of strong‐field general relativity. Recently discovered binary pulsar systems may provide additional tests. Future and ongoing experiments, such as the Gravity Probe B Gyroscope Experiment, satellite tests of the Equivalence Principle, and tests of gravity at short distance to look for extra spatial dimensions could constrain extensions of general relativity. Laser interferometric gravitational‐wave observatories on Earth and in space may provide new tests of gravitational theory via detailed measurements of the properties of gravitational waves.
Quasar absorption spectral data indicate the presence of a spatial gradient in the electromagnetic fine-structure constant α on cosmological length scales. We point out that experiments with accelerometers, including torsion pendula and atom interferometers, can be used as sensitive probes of cosmological spatial gradients in the fundamental constants of nature, which give rise to equivalence-principle-violating forces on test masses. Using laboratory data from the Eöt-Wash experiment, we constrain spatial gradients in α along any direction to be |∇α/α|<6.6×10−4(Glyr)−1 at 95% confidence level. Our result represents an order of magnitude improvement over laboratory bounds from clock-based searches for a spatial gradient in α directed along the observed cosmological α-dipole axis. Improvements to accelerometer experiments in the foreseeable future are expected to provide sufficient sensitivity to test the cosmological α dipole seen in astrophysical data.
We propose a simple model based on the assumption that the varying fine structure constant α is an effect of the cosmological expansion to investigate the relation between the varying α and the cosmological components. For a spatially flat, homogeneous, and isotropic universe, the current proportion of cosmological components and age of the universe predicted by the model are consistent with the cosmological observations. Furthermore, the predicted current variation rate of α is also close to the atomic clock measurements. For the early universe, we predict a very strict constraint, which is compatible with the upper limit given by the investigations of cosmic microwave background and big bang nucleosynthesis.
This work demonstrates an analytical protocol for high precision Sm isotope analysis by thermal ionization mass spectrometry (TIMS) using a Pt activator. The method permits precise measurements of small aliquots (1–20 ng) of Sm on single Re filament using a modified static-total evaporation technique. This study represents the first attempt to use such protocols for Sm isotope analyses while reducing the loading size of Sm for TIMS. The method could potentially be deployed to study geological, meteorites and lunar samples containing low Sm concentrations, to monitor neutron irradiation exposure based on 149,150Sm, or to measure Sm isotopic composition in other types of nuclear samples.
In order to more accurately measure the fine splitting of resonance lines at an epoch corresponding to the redshift z ≈ 3, we carried out spectroscopic observations of the QSOs HS 1946+76, S5 0014+81, and S4 0636+68 with resolution FWHM ≈ 20 km s-1, which is high for quasars, and signal-to-noise ratio S/N ≈ 15 using the 6-m Special Astrophysical Observatory telescope. A study of multicomponent Si IV line profiles made it possible to determine kinematic properties of individual gas clouds in the galaxies that happened to be along the line of sight. An analysis of the relative fine splitting Δλ/λ of the Si IV resonance lines in absorption spectra of the quasars has yielded a new constraint on the possible variation of the fine-structure constant α = e2/ℏc at the epoch of line formation z = 2.8-3.1: (Δα/α)z = (0.2 ± 0.7) × 10-4. The upper limit on the rate of change of α averaged over ∼10 Gyr (at 2 σ level) is |α̇/α| < 1.6 × 10-14 yr-1. This constraint is more stringent than those obtained from previous astronomical observations and precise laboratory measurements.
Gamow was one of the pioneers who studied the possible variability of fundamental physical constants. Some versions of modern Grand Unification theories do predict such variability. The paper is concerned with three of the constants: the fine-structure constant , the ratio of the proton massm
p to the electron massm
e, and the ratio of the neutron massm
n tom
e. It is shown on the basis of the quasar spectra analysis, that all the three constants revealed no statistically significant variation over the last 90% of the life time of the Universe. At the 2 significance level, the following upper bounds are obtained for the epoch corresponding to the cosmological redshiftsz2–3: /<1.510–3, m
p/m
p<210–3, and m/m<310–4, where x is a possible deviation of a quantityx from its present value,m=m
p+m
n, and the nucleon masses are in units ofm
e. (According to new observational data which became known most recently, m
p/m
p<210–4) In addition a possible anisotropy of the high-redshift fine splitting over the celestial sphere is checked. Within the relative statistical error 3 < 1% the values of turned out to be the same in various quadrants of the celestial sphere, which corresponds to their equality in causally disconnected areas. However, at the 2 level a tentative anisotropy of estimated / values is found in directions that approximately coincide with the direction of the relic microwave background anisotropy.The revealed constraints serve as criteria for selection of those theoretical models which predict variation of ,m
p orm
n with the cosmological time.
The development of on-line mass separators, which provide long chains of isotopes extending far off stability, immediately raised the question of how to gain access to the basic nuclear ground-state properties of these exotic nuclei—their spins, moments, radii, and masses. In general, the amount of radioactive material produced at these facilities is too small to form beams or targets for any kind of scattering or nuclear-reaction experiment. On the other hand, the traditional spectroscopic methods, namely, atomic, nuclear, and mass spectroscopy, have turned out to be very suitable for this application since they are easily adapted to the special on-line conditions.
Consistent bounds for the simultaneous variations of fundamental constants in the standard model of fundamental interactions are obtained from astronomical, astrophysical, and geophysical data. These bounds exclude the Dirac large-number hypothesis and, in general, any theory demanding a large variation of the fundamental constants. They also impose severe constraints on Kaluza-Klein and superstring theories, and should be considered as strong tests of the equivalence principle.
We describe a new test for possible variations of the fine structure constant alpha by comparisons of rates between clocks based on hyperfine transitions in alkali atoms with different atomic number Z. H-maser, Cs, and Hg(+) clocks have a different dependence on alpha via relativistic contributions of order (Z-alpha)(sup 2). Recent H-maser vs Hg(+) clock comparison data improve laboratory limits on a time variation by 100-fold to give dot-alpha less than or equal to 3.7 x 10(exp -14)/yr. Future laser cooled clocks (Be(+), Rb, Cs, Hg(+), etc.), when compared, will yield the most sensitive of all tests for dot-alpha/alpha.
A current-current model for weak interactions is used to show that the
weak-interaction contribution to the ground-state energies of typical
nuclei is about one part in 100 million of their rest masses. By
comparing this contribution with the results of recent versions of the
Eotvos experiments, it is concluded that weak-interaction energies obey
the principle of equivalence to better than one part in 100, thus
refuting claims that those experiments did not test weak-interaction
effects.
The author reviews the status of our understanding of nucleosynthesis of the light nuclei (Z<6). The standard view today is that these elements are, for the most part, generated by two different processes: first, thermonuclear reactions in the early universe (big-bang nucleosynthesis or (BBN), and second, galactic cosmic-ray-induced spallation reactions (GCR) in cold interstellar atoms. A third contribution comes from stellar processes. The arguments in favor of this view are presented. Numerous astrophysical and cosmological implications are discussed, such as the baryonic density, the possible existence of baryonic dark matter and of nonbaryonic (exotic) matter, the constraints imposed on new particle physics, the leptonic number of the universe, the increase in cosmic entropy since primordial nucleosynthesis, and the constancy of the "constants" of physics.
CONTENTS
1. Introduction 937
2. History of the Discovery of the Natural Reactor 938
3. Reactor Parameters 939
4. Consequences of the Discovery of the Oklo Phenomenon 942
Literature 943
We report on new tests that improve our previous (2009-2010) estimates of the
electron-to-proton mass ratio variation, mu = m_e/m_p. Subsequent observations
(2011-2013) at the Effelsberg 100-m telescope of a sample of eight molecular
cores from the Milky Way disk reveal systematic errors in the measured sky
frequencies varying with an amplitude +/-0.01 km/s during the exposure time.
The averaged offset between the radial velocities of the NH3(1,1), HC3N(2-1),
HC5N(9-8), HC7N(16-15), HC7N(21-20), and HC7N(23-22) transitions gives Delta V
= 0.002 +/- 0.015 km/s [3 sigma confidence level (C.L.)]. This value, when
interpreted in terms of Delta mu/mu = (mu_obs - mu_lab)/mu_lab constraints the
mu-variation at the level of Delta mu/mu < 2x10^{-8} (3 sigma C.L.), which is
the most stringent limit on the fractional changes in mu based on radio
astronomical observations.
We discuss the fundamental constants of physics within the Standard Model of particle physics. In this model there are 28 fundamental constants, e.g. the constant of gravity or the fine-structure constant. We consider possible changes of these constants on the cosmological time scale.
Isotopic dilution technique and mass spectrometry are used in order to measure isotopic compositions and concentrations of some particular elements on the Oklo sample KN50-3548, which are interesting for describing the nuclear reaction. These analyses give coherent results leading to the determination of the following parameters: neutron fluence, spectrum index, total number of fissions relative to uranium, and percentage of 238U and 239Pu fissions. From the percentage of plutonium fissions, the duration of the nuclear reaction is estimated to be 800,000 years. The age of the nuclear reaction is measured from the lead analysis and from the number of uranium fissions; these two determinations give respectively d = 1730 ± 10 m.y. and d = 2000 ± 100 m.y. The second method, based on the assumption that uranium and rare earths have not migrated, could mean that the nuclear reaction might be older than the Francevillian. It is also shown that no contamination by natural elements has occurred for lead, rare earths, palladium and rare gases, after the reaction.
CONTENTS 1. Introduction 937 2. History of the Discovery of the Natural Reactor 938 3. Reactor Parameters 939 4. Consequences of the Discovery of the Oklo Phenomenon 942 Literature 943
We calculate ground-state masses for 4678 nuclei ranging from ¹â¶O to ³¹â¸122 by means of an improved version of the macroscopic-microscopic model employed in our 1981 mass calculation, which uses a Yukawa-plus-exponential model for the macroscopic term and a folded-Yukawa single-particle potential as starting point for the microscopic term. Some of the new features now incorporated are a new model for the average pairing strength, the solution of the microscopic pairing equations by use of the Lipkin-Nogami method with approximate particle-number conservation, the use of experimental mass uncertainties in determining the model parameters, and an estimation of the theoretical error of the model by application of the maximum-likelihood method. Only five parameters are determined from least-squares fitting to the nuclear masses; the other constants in the model are taken from previous work with no adjustment. The resulting theoretical error in the calculated ground-state masses fo 1593 nuclei ranging from ¹â¶O to ²â¶Â³106 is 0.832 MeV. We also extend the calculation to some additional nuclei in the heavy and superheavy region that were not considered in 1981. The present calculation represents an interim report on a project in which we plan to make further improvements and extend the region of nuclei considered to the neutron and proton drip lines. copyright 1988 Academic Press, Inc.
RECENT wave-length measurements by R. Minkowski and O. C. Wilson1 of spectral lines of H, N II, O I, O II, Ne III and Ne V for the colliding galaxies identified with the radio source Cygnus A permit comparison of galaxy values of physical constants with local values. In particular, radio measures by A. E. Lilley and E. F. McClain2, in combination with the optical measures, permit estimates on the ratio of galactic to local values of the fine structure constant, α, and the proton gyromagnetic ratio, g. The observed system is estimated to be 3 × 108 light years from us on the Humason, Mayall, Sandage scale3.
A summary of recent observational evidence bearing on the question of the possible variation of the natural constants with time. No conclusive evidence of variation is found.
This document is the latest in a series of compilations of fission yield data. Fission yield measurements reported in the open literature and calculated charge distributions have been used to produce a recommended set of yields for the fission products. The original data with reference sources, and the recommended yields axe presented in tabular form. These include many nuclides which fission by neutrons at several energies. These energies include thermal energies (T), fission spectrum energies (F), 14 meV High Energy (H or HE), and spontaneous fission (S), in six sets of ten each. Set A includes U235T, U235F, U235HE, U238F, U238HE, Pu239T, Pu239F, Pu241T, U233T, Th232F. Set B includes U233F, U233HE, U236F, Pu239H, Pu240F, Pu241F, Pu242F, Th232H, Np237F, Cf252S. Set C includes U234F, U237F, Pu240H, U234HE, U236HE, Pu238F, Am241F, Am243F, Np238F, Cm242F. Set D includes Th227T, Th229T, Pa231F, Am241T, Am241H, Am242MT, Cm245T, Cf249T, Cf251T, Es254T. Set E includes Cf250S, Cm244S, Cm248S, Es253S, Fm254S, Fm255T, Fm256S, Np237H, U232T, U238S. Set F includes Cm243T, Cm246S, Cm243F, Cm244F, Cm246F, Cm248F, Pu242H, Np237T, Pu240T, and Pu242T to complete fission product yield evaluations for 60 fissioning systems in all. This report also serves as the primary documentation for the second evaluation of yields in ENDF/B-VI released in 1993.
This document is the ninth in a series of compilations of fission yield data made at Vallecitos Nuclear Center in which fission yield measurements reported in the open literature and calculated charge distributions have been utilized to produce a recommended set of yields for the known fission products. The original data with reference sources, as well as the recommended yields are presented in tabular form for the fissionable nuclides U-235, Pu-239, Pu-241, and U-233 at thermal neutron energies; for U-235, U-238, Pu-239, and Th-232 at fission spectrum energies; and U-235 and U-238 at 14 MeV. In addition, U-233, U-236, Pu-240, Pu-241, Pu-242, Np-237 at fission spectrum energies; U-233, Pu-239, Th-232 at 14 MeV and Cf-252 spontaneous fission are similarly treated. For 1979 U234F, U237F, Pu249H, U234He, U236He, Pu238F, Am241F, Am243F, Np238F, and Cm242F yields were evaluated. In 1980, Th227T, Th229T, Pa231F, Am241T, Am241H, Am242Mt, Cm245T, Cf249T, Cf251T, and Es254T are also evaluated.
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.
A systematic investigation of the isotope shifts of all natural Samarium isotopes was performed in 15 lines of the Sm I spectrum using the laser-atomic-beam technique. The observed lines correspond to transitions between the ground configuration 4f
66s
2 and the upper configurations 4f
66s6p and 4f
55d6s
2. In one line a contribution of hyperfine-structure second-order effects to the isotope shift of the odd isotopes could be demonstrated. The measured isotope shifts have been separated in all lines into field shift and mass shift contributions assuming the specific mass shift to be zero in pures
2-sp transitions. From the field shift of the pures
2-sp transitions the changes in mean-square nuclear charge radii, δ<r
2>, have been evaluated for all natural Sm isotopes (in fm2): [144, 148] 0.517(27); [148, 150] 0.303(16); [150, 152] 0.423(22); [152, 154] 0.230(12); [147, 148] 0.152(8); [148, 149] 0.092(5). There is good consistency with recent muonic x-ray measurements of the changes in the Barrett nuclear charge radii,δR
k
, of the even Sm isotopes.
The scientific literature is rich with studies of non-standard primodial nucleosynthesis. We review a number of these variants on the simplest standard big bang (SBB) nucleosynthesis model and discuss some of the impact these studies have had on cosmology and particle physics. Primordial nucleosynthesis is one of the earliest probes of the universe, and non-standard nucleosynthesis models allow for an exploration of the range of conditions which might have prevailed during the first few minutes. In particular, nonstandard models often allow for a larger range of conditions to be present in the early universe than those allowed by the SBB while satisfying observational constraints such as the inferred primordial isotopic abundances and the number of neutrino species derived from recent e+e− collider experiments. By considering alternatives to the SBB we can also determine the model dependence of the constraints imposed on particle physics and cosmology from primordial nucleosynthesis.
It is pointed out that string-loop modifications of the low-energy matter couplings of the dilation may provide a mechanism for fixing the vacuum expectation value of a massless dilation in a way which is naturally compatible with existing experimental data. Under a certain assumption of universality of the dilation coupling functions, the cosmological evolution of the graviton-dilaton-matter system is shown to drive the dilaton towards values where it decouples from matter (“Least Coupling Principle”). Quantitative estimates are given of the residual strength, at the present cosmological epoch, of the coupling to matter of the dilaton. The existence of a weakly coupled massless dilaton entails a large spectrum of small, but non-zero, observable deviations from general relativity. In particular, our results provide a new motivation for trying to improve by several orders of magnitude the various experimental tests of Einstein's Equivalence Principle (universality of free fall, constancy of the constants, etc.).
The fine structure constant at red shifts Δλ / λ≈0.2, corresponding to an epoch around two billion years ago, has been determined using the wavelengths of a pair of O III emission lines measured in the spectra of five radio galaxies. We find α(z=0.2) / α(lab)=1.001±0.002 probable error.
[NOTE: This 1983 preprint is being uploaded to arXiv.org after the death of its author, who supported online distribution of his work. Contact info of the submitter is at http://ilya.cc .] The positions of neutron resonances have been shown to be highly sensitive to the variation of fundamental nuclear constants. The analysis of the measured isotopic shifts in the natural fossil reactor at Oklo gives the following restrictions on the possible rates of the interaction constants variation: strong ~2x10^-19 yr^-1, electromagnetic ~5x10^-18 yr^-1, weak ~10^-12 yr^-1. These limits permit to exclude all the versions of nuclear constants contemporary variation discussed in the literature. URL: http://alexonline.info >. For more recent analyses see hep-ph/9606486, hep-ph/0205206 and astro-ph/0204069 .
It is pointed out that string-loop effects may generate matter couplings for the dilaton allowing this scalar partner of the tensorial graviton to stay massless while contributing to macroscopic gravity in a way naturally compatible with existing experimental data. Under a certain assumption of universality of the dilaton coupling functions (possibly realized through a discrete symmetry such as S-duality), the cosmological evolution drives the dilaton towards values where it decouples from matter. At the present cosmological epoch, the coupling to matter of the dilaton should be very small, but non zero. This provides a new motivation for improving the experimental tests of Einstein's Equivalence Principle. Comment: 5 pages, PLAIN TEX
We report new upper limits on any possible long-term time variation of the
ratio of the electron to proton masses, , the fine-structure
constant, (), and the quantity , where is
the proton gyromagnetic ratio. These limits are based on extremely high
precision observations of H, Si, C and H in high-redshift
quasar absorption lines. They amount to 95\% confidence ranges of yr for (),
yr for \ and yr for
, where the elapsed time has been computed for a
cosmology with \hnought = 75 km s Mpc and \qnought = 0.5.
) 340. 1141 A.I. Shlyakhter, Direct test for the constancy of fundamental nuclear constants using the Oklo natural reactor
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