Time variation of the fine structure constant in the early universe and the Bekenstein model

Free access article

Issue		A&A Volume 478, Number 3, February II 2008


Page(s)		675 - 684
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20078605

A&A 478, 675-684 (2008)
DOI: 10.1051/0004-6361:20078605

Time variation of the fine structure constant in the early universe and the Bekenstein model

M. E. Mosquera¹, C. G. Scóccola^{1, 2}, S. J. Landau³, and H. Vucetich¹

¹ Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, cp 1900 La Plata, Argentina
e-mail: [mmosquera;cscoccola;vucetich]@fcaglp.unlp.edu.ar
² Instituto de Astrofísica La Plata
³ Departamento de Física, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria - Pab. 1, 1428 Buenos Aires, Argentina
e-mail: slandau@df.uba.ar

(Received 3 September 2007 / Accepted 4 November 2007)

Abstract
Aims.We calculate the bounds on the variation in the fine structure constant at the time of primordial nucleosynthesis and at the time of neutral hydrogen formation. We used these bounds and other bounds from the late universe to test the Bekenstein model.
Methods.We modified the Kawano code, CAMB, and CosmoMC to include the possible variation in the fine structure constant. We used observational primordial abundances of D, ⁴He, and ⁷Li, recent data from the cosmic microwave background, and the 2dFGRS power spectrum, to obtain bounds on the variation in $\alpha$ . We calculated a piecewise solution to the scalar field equation of the Bekenstein model in two different regimes: i) matter and radiation, ii) matter and cosmological constant. We match both solutions with the appropriate boundary conditions. We performed a statistical analysis, using the bounds obtained from the early universe and other bounds from the late universe to constrain the free parameters of the model.
Results.Results are consistent with no variation in $\alpha$ for the early universe. Limits on $\alpha$ are inconsistent with the scale length of the theory l being larger than the Planck scale.
Conclusions.In order to fit all observational and experimental data, the assumption l > $L_{\rm p}$ implied in Bekenstein's model has to be relaxed.

Key words: early Universe -- cosmology: theory -- cosmic microwave background

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