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The rigid-intensity-shift model of differential phase contrast scanning transmission electron microscopy (DPC-STEM) imaging assumes that the phase gradient imposed on the probe by the sample causes the diffraction pattern intensity to shift…

Instrumentation and Detectors · Physics 2018-04-25 L. Clark , H. G. Brown , D. M. Paganin , M. J. Morgan , T. Matsumoto , N. Shibata , T. C. Petersen , S. D. Findlay

We consider the problem of the evolution of the fine structure coefficient alpha under the assumption that the scalar field coupling to the Maxwell term satisfies the condition mt>>1 for coherent dark matter oscillations. In this case we…

Astrophysics · Physics 2009-11-10 M. G. Barnett , R. Dick , K. E. Wunderle

Higher-dimensional theories have the remarkable feature of predicting a time (and hence redshift) dependence of the `fundamental' four dimensional constants on cosmological timescales. In this paper we update the bounds on a possible…

We present an up-to-date analysis for a precise determination of the effective fine structure constant and discuss the prospects for future improvements. We advocate to use a determination monitored by the Adler function which allows us to…

High Energy Physics - Phenomenology · Physics 2008-11-07 F. Jegerlehner

We derive a redshift drift formula for the spherically symmetric inhomogeneous pressure Stephani universes which are complementary to the spherically symmetric inhomogeneous density Lema\^itre-Tolman-Bondi models. We show that there is a…

Cosmology and Nongalactic Astrophysics · Physics 2013-03-14 Adam Balcerzak , Mariusz P. Dabrowski

Using a gauge-invariant formalism we derive and solve the perturbed cosmological equations for the BSBM theory of varying fine structure 'constant'. We calculate the time evolution of inhomogeneous perturbations of the fine structure…

General Relativity and Quantum Cosmology · Physics 2009-11-07 John D. Barrow , D. F. Mota

Dynamical scalar fields in an effective four-dimensional field theory are naturally expected to couple to the rest of the theory's degrees of freedom, unless some new symmetry is postulated to suppress these couplings. In particular, a…

Recent observations on the quasar absorption spectra supply evidence for the variation of the fine structure constant $\alpha$. In this paper, we propose another interpretation of the observational data on the quasar absorption spectra: a…

General Relativity and Quantum Cosmology · Physics 2012-02-15 Zhe Chang , Sai Wang , Xin Li

We review some string-inspired theoretical models which incorporate a correlated spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo;…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Thibault Damour

We study the change of the effective fine structure constant in the cosmological models of a scalar field with a non-vanishing coupling to the electromagnetic field. Combining cosmological data and terrestrial observations we place…

High Energy Physics - Phenomenology · Physics 2009-11-10 E. J. Copeland , N. J. Nunes , M. Pospelov

A phenomenological model is proposed to explain the recent observed cosmological variation of the fine structure constant as an effect of the quantum vacuum, assuming a flat universe with cosmological constant $\Lambda$ in the cases…

Astrophysics · Physics 2010-12-17 Antonio F. Rañada

The existing observational data on possible variations of fundamental physical constants (FPC) confirm more or less confidently only a variability of the fine structure constant $\alpha$ in space and time. A model construction method is…

General Relativity and Quantum Cosmology · Physics 2015-06-12 K. A. Bronnikov , V. N. Melnikov , S. G. Rubin , I. V. Svadkovsky

We use astrophysical and atomic clock tests of the stability of the fine-structure constant $\alpha$, together with Type Ia supernova and Hubble parameter data, to constrain the simplest class of dynamical dark energy models where the same…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-12 C. J. A. P. Martins , A. M. M. Pinho

Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu$, are an optimal probe of new physics. There is a growing interest in these…

Cosmology and Nongalactic Astrophysics · Physics 2016-07-07 A. C. O. Leite , C. J. A. P. Martins

In this investigation, we perform an observational statistical analysis in the theory of $ f(R, L_m) $ gravity. The proposed theoretical model is based on the Ricci scalar's non-linear contribution. We use a distinct parameterization for…

General Relativity and Quantum Cosmology · Physics 2024-08-30 J. K. Singh , Shaily , Akanksha Singh , Harshna Balhara , Joao R. L. Santos

The evolution of the expansion rate of the Universe results in a drift in the redshift of distant sources over time. A measurement of this drift would provide us with a direct probe of expansion history. The Lyman alpha forest has been…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Madhura Killedar , Geraint F. Lewis

Development of fundamental physics relies on the constancy of various fundamental quantities such as the fine structure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an…

Astrophysics · Physics 2009-11-10 H. Chand , R. Srianand , P. Petitjean , B. Aracil

We discuss how dynamical dark energy universes with exotic singularities may be distinguished from the standard $\Lambda$CDM model on the basis of their redshift drift signal, for which measurements both in the acceleration phase and in the…

Cosmology and Nongalactic Astrophysics · Physics 2014-04-23 Tomasz Denkiewicz , Mariusz P. Dabrowski , Carlos J. A. P. Martins , Pauline Vielzeuf

Spatial and temporal variations in the electron-to-proton mass ratio, mu, and in the fine-structure constant, alpha, are predicted in non-Standard models aimed to explain the nature of dark energy. Among them the so-called chameleon-like…

Cosmology and Nongalactic Astrophysics · Physics 2009-11-20 S. A. Levshakov , I. I. Agafonova , P. Molaro , D. Reimers
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