The Experts below are selected from a list of 301389 Experts worldwide ranked by ideXlab platform
H Farajollahi - One of the best experts on this subject based on the ideXlab platform.
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universe acceleration and fine Structure Constant variation in bsbm theory
Journal of Cosmology and Astroparticle Physics, 2012Co-Authors: H Farajollahi, Amin SalehiAbstract:In this work we investigate the utility of using SNe Ia observations in constraining the cosmological parameters in BSBM theory where a scalar field is responsible for both fine Structure Constant variation and late time universe acceleration. The model is discussed in the presence of an exponential self potential for the scalar field. Stability and phase space analysis of the solutions are studied. The model is tested against observational data for Hubble parameter and quasar absorption spectra. With the best fitted model parameters, the theory predicts a good match with the experimental results and exhibits fine Structure Constant variation. The analysis also predicts the recent universe acceleration and possible phantom crossing in future.
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universe acceleration and fine Structure Constant variation in bsbm theory
arXiv: General Relativity and Quantum Cosmology, 2012Co-Authors: H Farajollahi, Amin SalehiAbstract:In this work we investigate the utility of using SNe Ia observations in constraining the cosmological parameters in BSBM theory where a scalar field is responsible for both fine Structure Constant variation and late time universe acceleration. The model is discussed in the presence of an exponential self potential for the scalar field. Stability and phase space analysis of the solutions are studied. The model is tested against observational data for Hubble parameter and quasar absorption spectra. With the best fitted model parameters, the theory predicts a good match with the experimental results and exhibits fine Structure Constant variation. The analysis also shows that for the equation of state parameter, recent universe acceleration and possible phantom crossing in future is forecasted.
Haoyu Qi - One of the best experts on this subject based on the ideXlab platform.
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f t theories and varying fine Structure Constant
Physics Letters B, 2011Co-Authors: Haoyu QiAbstract:Abstract In analogy to f ( R ) theory, recently a new modified gravity theory, namely the so-called f ( T ) theory, has been proposed to drive the current accelerated expansion without invoking dark energy. In the present work, by extending Bisabrʼs idea, we try to constrain f ( T ) theories with the varying fine Structure “Constant”, α ≡ e 2 / ℏ c . We find that the constraints on f ( T ) theories from the observational Δ α / α data are very severe. In fact, they make f ( T ) theories almost indistinguishable from ΛCDM model.
Charles L Steinhardt - One of the best experts on this subject based on the ideXlab platform.
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constraints on field theoretical models for variation of the fine Structure Constant
Physical Review D, 2005Co-Authors: Charles L SteinhardtAbstract:Recent theoretical ideas and observational claims suggest that the fine Structure Constant $\ensuremath{\alpha}$ may be variable. We examine a spectrum of models in which $\ensuremath{\alpha}$ is a function of a scalar field. Specifically, we consider three scenarios: oscillating $\ensuremath{\alpha}$, monotonic time variation of $\ensuremath{\alpha}$, and time-independent $\ensuremath{\alpha}$ 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 Oklo subnuclear reactor on models with monotonic timelike variation of $\ensuremath{\alpha}$. One particular model with spatial variation is consistent with all current experimental and observational measurements, including those from two seemingly conflicting measurements of the fine Structure Constant using the many multiplet method on absorption lines.
Ivan A. Cardenas - One of the best experts on this subject based on the ideXlab platform.
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Variation of the fine Structure Constant
arXiv: General Physics, 2016Co-Authors: Anton A. Lipovka, Ivan A. CardenasAbstract:In present paper we evaluate the fine Structure Constant variation which should take place as the Universe is expanded and its curvature is changed adiabatically. This changing of the fine Structure Constant is attributed to the energy lost by physical system (consist of baryonic component and electromagnetic field) due to expansion of our Universe. Obtained ratio (d alpha)/alpha = 1. 10{-18} (per second) is only five times smaller than actually reported experimental limit on this value. For this reason this variation can probably be measured within a couple of years. To argue the correctness of our approach we calculate the Planck Constant as adiabatic invariant of electromagnetic field, from geometry of our Universe in the framework of the pseudo- Riemannian geometry. Finally we discuss the double clock experiment based on Al+ and Hg+ clocks carried out by T. Rosenband et al. (Science 2008). We show that in this particular case there is an error in method and this way the fine Structure Constant variation can not be measured if the fine Structure Constant is changed adiabatically.
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Variation of the fine Structure Constant
viXra, 2016Co-Authors: Anton A. Lipovka, Ivan A. CardenasAbstract:In present paper we evaluate the fine Structure Constant variation which should take place as the Universe is expanded and its curvature is changed adiabatically. This changing of the fine Structure Constant is attributed to the energy lost by physical system (consist of baryonic component and electromagnetic field) due to expansion of our Universe. Obtained ratio · α/α = 1·10 −18 (per second) is only five times smaller than actually reported experimental limit on this value. For this reason this variation can probably be measured within a couple of years. To argue the correctness of our approach we calculate the Planck Constant as adia-batic invariant of electromagnetic field, from geometry of our Universe in the framework of the pseudo-Riemannian geometry. Finally we discuss the double clock experiment based on Al + and Hg + clocks carried out by T. Rosenband et al. (Science 2008). We show that in this particular case there is an error in method and this way the value ·
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Variation of the fine Structure Constant caused by the expansion of the Univerce
arXiv: General Physics, 2016Co-Authors: Anton A. Lipovka, Ivan A. CardenasAbstract:In present paper we evaluate the fine Structure Constant variation, that should take place as the Universe expands and its curvature is changed adiabatically. Such variation of the fine Structure Constant is attributed to an energy losses by an extended physical system (consist of baryonic component and electromagnetic field) due to expansion of our Universe. Obtained ratio (d alpha)/alpha = 1. 10{-18} (per second) is only five times smaller than actually reported experimental limit on this value. For this reason obtained variation can probably be measured within a couple of years. To argue the correctness of our approach we calculate the Planck Constant as adiabatic invariant of the electromagnetic field propagated on a manifold characterized by slowly varied geometry, in the framework of the pseudo- Riemannian geometry. Finally we discuss the double clock experiment based on Al+ and Hg+ clocks carried out by T. Rosenband et al. (Science 2008). We show that in this case (when the fine Structure Constant is changed adiabatically) the method based on double clock experiment can not be applied to measure the fine Structure Constant variation.
Asantha Cooray - One of the best experts on this subject based on the ideXlab platform.
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constraints on spatial variations in the fine Structure Constant from planck
The Astrophysical Journal, 2014Co-Authors: Jon Obryan, Joseph Smidt, Francesco De Bernardis, Asantha CoorayAbstract:We use the cosmic microwave background (CMB) anisotropy data from Planck to constrain the spatial fluctuations of the fine-Structure Constant α at a redshift of 1100. We use a quadratic estimator to measure the four-point correlation function of the CMB temperature anisotropies and extract the angular power spectrum fine-Structure Constant spatial variations projected along the line of sight at the last scattering surface. At tens of degree angular scales and above, we constrain the fractional rms fluctuations of the fine-Structure Constant to be (δα/α)rms < 3.4 × 10–3 at the 68% confidence level. We find no evidence for a spatially varying α at a redshift of 103.
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constraints on spatial variations in the fine Structure Constant from planck
arXiv: Cosmology and Nongalactic Astrophysics, 2013Co-Authors: Jon Obryan, Joseph Smidt, Francesco De Bernardis, Asantha CoorayAbstract:We use the Cosmic Microwave Background (CMB) anisotropy data from Planck to constrain the spatial fluctuations of the fine-Structure Constant \alpha. Through Thompson scattering of CMB photons, spatial anisotropies of \alpha lead to higher-order correlations in the CMB anisotropies. We use a quadratic estimator based on the four-point correlation function of the CMB temperature anisotropy to extract the angular power spectrum of the spatial variation of the fine-Structure Constant projected along the line of sight at the last scattering surface. At tens of degree angular scales and above, we constrain the rms fluctuations of the fine Structure Constant to be \delta \alpha/\alpha_0= (1.34 +/- 5.82) x 10^-2 at the 95% confidence level with respect to the standard value \alpha_0. We find no evidence for a spatially varying \alpha at a redshift of 10^3.
