We analyze different data of the variation of the fine structure constant obtained with different methods to check their consistency.We test consistency using the modified Student test and confidence intervals. We split the data sets in smaller intervals. A criterion for this selection is proposed. Results show consistency for reduced intervals for each pair of data sets considered. Results are at variance with the ones obtained considering mean values over the whole interval.
We present measurements of absorption by the 21cm hyperfine transition of neutral hydrogen toward radio sources at substantial look-back times. These data are used in combination with observations of rotational transitions of common interstellar molecules, to set limits on the evolution of the fine structure constant: (dot alpha)/alpha < 3.5e-15/yr to a look-back time of 4.8 Gyr. The neutral hydrogen observations employed Very Long Baseline Interferometry in order to mitigate the substantial uncertainty arising from the fact that observations at very different wavelengths may probe different l…
It is proposed a model of Kaluza Klein that does make the quantification of the electric charges without magnetic monopoles. This model of Kaluza Klein allows to calculate de radius of compactation proposed for Klein. The model is of Kaluza Klein, but it has consequences in the theory of the quantum strings, and it is possible to indicate a manner of to test the existence of the quantum strings.The model indicates that: if the quantum strings exist really, the cosmological variation of the fine structure constant would do quantum jumps. If this variation is continuous, the quantum strings does…
Radio astronomical observations have very poor signal to noise ratios, unlike in other disciplines. On the other hand, it is possible to observe the object of interest for long time intervals as well as using a wider bandwidth. Traditionally, by averaging in time and in frequency, it has been possible to improve the signal to noise ratio of astronomical observations to improve the dynamic range. This is possible due to the inherent assumption that the object of interest in the sky is invariant over time and the frequency range of observation. However, in reality this assumption does not hold, …
We have used the Very Long Baseline Array (VLBA) and the Very Large Array (VLA) to image Galactic neutral hydrogen in absorption towards four compact extragalactic radio sources with 10 milliarcsecond resolution. Previous VLBA data by Faison et al (1998) have shown the existence of prominent structures in the direction of the extragalactic source 3C~138 with scale sizes of 10-20 AU with changes in HI optical depth in excess of 0.8 $\pm$ 0.1. In this paper we confirm the small scale \hi optical depth variations toward 3C~147 suggested earlier at a level up to 20 % $\pm$ 5% . The sources 3C~119,…
We present initial results on the use of Mixture Models for density estimation in large astronomical databases. We provide herein both the theoretical and experimental background for using a mixture model of Gaussians based on the Expectation Maximization (EM) Algorithm. Applying these analyses to simulated data sets we show that the EM algorithm - using the both the AIC & BIC penalized likelihood to score the fit - can out-perform the best kernel density estimate of the distribution while requiring no ``fine-tuning'' of the input algorithm parameters. We find that EM can accurately recover th…
We consider astronomical and local bounds on time variation of fundamental constants to test some generic Kaluza-Klein-like models and some particular cases of Beckenstein theory. Bounds on the free parameters of the different theories are obtained. Furthermore, we find that none of the proposed models, is able to explain recent results [Webb99,Webb00] claiming an observed variation of the fine structure constant from quasar absorption systems at redshifts $0.5<z<3$.
A brief note on the time variation of the fine structure constant $α_{em}$; it is shown that such a variation should violate mass-energy conservation in the absence of proton decay.
In this paper, we outline the use of Mixture Models in density estimation of large astronomical databases. This method of density estimation has been known in Statistics for some time but has not been implemented because of the large computational cost. Herein, we detail an implementation of the Mixture Model density estimation based on multi-resolutional KD-trees which makes this statistical technique into a computationally tractable problem. We provide the theoretical and experimental background for using a mixture model of Gaussians based on the Expectation Maximization (EM) Algorithm. Appl…
(Abridged) Radio-astronomical observations of molecular cores in lines of NH3 (J,K)=(1,1), CCS J_N=2_1-1_0, HC3N J=5-4, and N2H+ J=1-0 are used to measure the relative radial velocity offsets, Delta V, between the NH3 (1,1) and other molecular transitions. Robust statistical analysis is applied to the n=207 individual measurements in the Perseus molecular cloud (PC), the Pipe Nebula (PN), and the infrared dark clouds (IRDCs) to deduce the mean value of Delta V and its uncertainty. The measured values of Delta V from the PC, PN, and IRDCs show statistically significant positive velocity shifts …
We calculate the dependence of atomic transition frequencies on the fine structure constant, $α= e^2/\hbar c$, for some ions of Ti, Mn, Na, C, and O. The results of these calculations will be used in the search for variation of alpha in quasar absorption spectra.
There are obvious discrepancies among various experimental constraints on the variation of the fine-structure constant, $α$. We attempt to discuss the issue in the framework of de Sitter invariant Special Relativity (${\cal SR}_{c,R}$) and to present a possible solution to the disagreement. In addition, on the basis of the observational data and the discussions presented in this Letter, we derive a rough theoretical estimate of the radius of the Universe.
We investigate the effect of variation in the value of the fine structure constant at high redshifts (recombination > z > 30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic hydrogen. We find that the 21 cm signal is very sensitive to the variations in the fine structure constant and it is so far the only probe of the fine structure constant in this redshift range. A change in the value of the fine structure constant by 1% changes the mean brightness temperature decrement of the CMB due to 21 cm absorption by > 5% over the redshift…
Here we apply the Generalized Second Law of Thermodynamics (GSL) to black holes accreting and emitting in the present Universe and derive upper limits on the variation in the gravitational constant G. The limits depend on how the gravitational mass M varies with G. Parameterizing M goes as G^n, if n > -1/2 (including n = 0), the GSL applied to the full range of black holes theoretically allowed in the present Universe does not constrain an increase in G but any decrease must be less than about |(1/G) dG/dt| = 10^-52 per second. If n < -1/2, the GSL does not constrain a decrease in G but any in…
Astronomical observations are suggesting that the fine structure constant varies cosmologically. We present an analysis on the consequences that these variations might induce on the electromagnetic field as a whole. We show that under these circumstances the electrodynamics in vacuum could be described by two fields, the ``standard'' Maxwell's field and a new scalar field. We provide a generalised Lorentz force which can be used to test our results experimentally.
We relate the reported variation in the value of the fine structure constant to a possible non-universality of the gravitational interaction with respect to different particle generations.
An unexpected secular increase of the Astronomical Unit, the length scale of the Solar System, has recently been reported by three different research groups (Krasinsky and Brumberg, Pitjeva, Standish). The latest JPL measurements amount to 7+-2 m cy^-1. At present, there are no explanations able to accommodate such an observed phenomenon, neither in the realm of classical physics nor in the usual four-dimensional framework of the Einsteinian General Relativity. The Dvali-Gabadadze-Porrati braneworld scenario, which is a multi-dimensional model of gravity aimed to the explanation of the observe…
We use the relativistic Hartree-Fock method, many-body perturbation theory and configuration-interaction method to calculate the dependence of atomic transition frequencies on the fine structure constant, alpha. The results of these calculations will be used in the search for variation of the fine structure constant in quasar absorption spectra.
The bound on the time variation of the fine structure constant ($α$) driven by the dynamics of quintessence scalar field which is coupled to electromagnetism is discussed using phenomenological quintessential models constrained by SNIa and CMB observations. We find that those models allowing early quintessence give the largest variation $Δα$ at the decoupling epoch. Furthermore, the fifth force experiments imply that $Δα/α$ is less than about 0.1%.
Various astronomical observations point towards the evidence for dark energy. One of the most mysterious problem is the coincidence problem: why dark energy becomes dominant only recently. We present a scenario based on extended quintessence models to explain the late-time domination of dark energy without severe fine-tuning of initial conditions and model parameters.
It is considered that quasars evolve into normal galaxies by means of expansion of matter. The order of magnitude of the expansion velocity can be estimated. The Doppler shift caused by such expansion explains the supposed variation of the fine structure constant. This variation has been based on observations of absorption lines of gas clouds seen against background quasars. These ideas maintain the constancy of the fine structure constant.
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 the fine-structure constant, 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 the fine-structure constan…
We put limits on the time variation of the electron mass in the early universe using observational primordial abundances of D, He4 and Li7, recent data from the Cosmic Microwave Background and the 2dFGRS power spectrum. Furthermore, we use these constraints together with other astronomical and geophysical bounds from the late universe to test Barrow-Magueijo's model for the variation in m_e. From our analysis we obtain -0.615 < Gω/c^4 < -0.045 (3σinterval) in disagreement with the result obtained in the original paper.
Motivated by recent astrophysical observations of quasar absorption systems, we formulate a simple theory where the electron to proton mass ratio $μ=m_{e}/m_{p}$ is allowed to vary in space-time. In such a minimal theory only the electron mass varies, with $α$ and $m_{p}$ kept constant. We find that changes in $μ$ will be driven by the electronic energy density after the electron mass threshold is crossed. Particle production in this scenario is negligible. The cosmological constraints imposed by recent astronomical observations are very weak, due to the low mass density in electrons. Unlike i…
We study dependence of the CMB temperature anisotropy spectrum on the value of the fine structure constant $α$ and the equation of state of the dark energy component of the total density of the universe. We find that bounds imposed on the variation of $α$ from the analysis of currently available CMB data sets can be significantly relaxed if one also allows for a change in the equation of state.
Recent theoretical ideas and observational claims suggest that the fine structure constant alpha may be variable. We examine a spectrum of models in which alpha is a function of a scalar field. Specifically, we consider three scenarios: oscillating alpha, monotonic time variation of alpha, and time-independent alpha that is spatially varying. We examine the constraints imposed upon these theories by cosmological observations, particle detector experiments, and ``fifth force'' experiments. These constraints are very strong on models involving oscillation, but cannot compete with bounds from the…
We show why a dynamically varying fine structure constant does not impact on the Webb group's analysis as suggested by Bekenstein. We also provide a limit on the size of a possible correction to the Dirac Hamiltonian caused by a perturbation due to a dynamically varying alpha in hydrogen.
Unification of the gauge couplings would imply that time variations of the fine structure constant are accompanied by calculable and very significant time variations in the QCD scale parameter $Λ_{QCD}$. Since $Λ_{QCD}$ is the dominant factor in setting the hadron masses, estimates made by simple variations of the fine structure constant may not provide meaningful limits. There may also be related variations in Yukawa couplings and the electroweak scale. Implications for the 21 cm hyperfine transition, big bang nucleosynthesis, and the triple alpha process are discussed. We find that the first…
Recent astrophysical observations indicate that the proton-electron mass ratio and the fine structure constant have gone through nontrivial time evolution. We discuss their time variation in the context of a dilaton runaway scenario with gauge coupling unification at the string scale $M_{\rm s}$. We show that the choice of adjustable parameters allows them to fit the same order magnitude of both variations and their (opposite) signs in such a scenario.
There are indications from the study of quasar absorption spectra that the fine structure constant $α$ may have been measurably smaller for redshifts $z>2.$ Analyses of other data ($^{149}$Sm fission rate for the Oklo natural reactor, variation of $^{187}$Re $β$-decay rate in meteorite studies, atomic clock measurements) which probe variations of $α$ in the more recent past imply much smaller deviations from its present value. In this work we tie the variation of $α$ to the evolution of the quintessence field proposed by Albrecht and Skordis, and show that agreement with all these data, as wel…
With the latest astronomical data including Cosmic Microwave Background (WMAP three year, CBI, ACBAR, VSA), Type Ia Supernova ("gold sample"), Galaxy Clustering (SDSS 3-D matter power, Lyman-$α$ forest and Baryon Acoustic Oscillating (BAO)), we make a global fitting to constrain the mass varying neutrinos. We find that the parameter $δ$, denoting time evolving of neutrino mass, is weakly constrained and the neutrino mass limit today can be relaxed at least by a factor of two. Adding data of $0\nu2β$ decay of Heidelberg-Moscow experiment to our analysis, we find that $δ$ can be constrained tigh…
The gravitational field produced by a domain wall acts as a medium with spacetime-dependent permittivity ε. Therefore, the fine structure constant α= e^2/4 πεwill be a time-dependent function at fixed position. The most stringent constraint on the time-variation of αcomes from the natural reactor Oklo and gives |\dotα/α| < few 10^{-17} yr^{-1}. This limit constrains the tension of a cosmic domain wall to be less than σ\lesssim 10^{-2} MeV^3, and then represents the most severe limit on the energy density of a cosmic wall stretching our Universe.
