Journal Article

The growth index of matter perturbations and modified gravity

Spyros Basilakos and Athina Pouri

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 4, pages 3761-3767
Published in print July 2012 | ISSN: 0035-8711
Published online July 2012 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2012.21168.x
The growth index of matter perturbations and modified gravity

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We place tight constraints on the growth index γ by using the recent growth history results of 2 degree Field Galaxy Redshift Survey (2dFGRS), Sloan Digital Sky Survey luminous red galaxy (SDSS-LRG), VIMOS-VLT Deep Survey (VVDS) and WiggleZ data sets. In particular, we investigate several parametrizations of the growth index γ(z) by comparing their cosmological evolution using observational growth rate data at different redshifts. Utilizing a standard likelihood analysis we find that the use of the combined growth data provided by the 2dFGRS, SDSS-LRG, VVDS and WiggleZ galaxy surveys puts the most stringent constraints on the value of the growth index. As an example, assuming a constant growth index we obtain that γ= 0.602 ± 0.055 for the concordance Λ cold dark matter (ΛCDM) expansion model. Concerning the Dvali–Gabadadze–Porrati (DGP) gravity model, we find γ= 0.503 ± 0.06, which is lower and almost 3σ away from the theoretically predicted value of . Finally, based on a time varying growth index we also confirm that the combined growth data disfavour the DGP gravity.

Keywords: cosmological parameters

Journal Article.  5077 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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