Probing nonstandard gravity with the growth index: a background independent analysis
Abstract
Measurements of the growth index of linear matter density fluctuations γ(z) provide a clue as to whether Einstein's field equations encompass gravity also on large cosmic scales, those where the expansion of the universe accelerates. We show that the information encoded in this function can be satisfactorily parameterized using a small set of coefficients γ{sub i}, in such a way that the true scaling of the growth index is recovered to better than 1% in most dark energy and dark gravity models. We find that the likelihood of current data, given this formalism and the Λ Cold Dark Matter (ΛCDM) expansion model of Planck, is maximal for γ{sub 0} = 0.74{sup +0.44}{sub −0.41} and γ{sub 1} = 0.01{sup +0.46}{sub −0.46}, a measurement compatible with the ΛCDM predictions (γ{sub 0} = 0.545, γ{sub 1} = −0.007). In addition, data tend to favor models predicting slightly less growth of structures than the Planck ΛCDM scenario. The main aim of the paper is to provide a prescription for routinely calculating, in an analytic way, the amplitude of the growth indices γ{sub i} in relevant cosmological scenarios, and to show that these parameters naturally define a space where predictions of alternative theories of gravitymore »
 Authors:
 Aix Marseille Université, Université de Toulon, CNRS, CPT UMR 7332, 13288, Marseille (France)
 INAF — Osservatorio Astronomico di Brera, Via Brera 28, Milano, via Bianchi 46, 23807 Merate (Italy)
 Publication Date:
 OSTI Identifier:
 22373554
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 05; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; COSMOLOGICAL MODELS; EINSTEIN FIELD EQUATIONS; EXPANSION; FLUCTUATIONS; GRAVITATION; NONLUMINOUS MATTER; SPACE; UNIVERSE
Citation Formats
Steigerwald, Heinrich, Marinoni, Christian, and Bel, Julien, Email: heinrich.steigerwald@cpt.univmrs.fr, Email: jbel@cpt.univmrs.fr, Email: christian.marinoni@cpt.univmrs.fr. Probing nonstandard gravity with the growth index: a background independent analysis. United States: N. p., 2014.
Web. doi:10.1088/14757516/2014/05/042.
Steigerwald, Heinrich, Marinoni, Christian, & Bel, Julien, Email: heinrich.steigerwald@cpt.univmrs.fr, Email: jbel@cpt.univmrs.fr, Email: christian.marinoni@cpt.univmrs.fr. Probing nonstandard gravity with the growth index: a background independent analysis. United States. doi:10.1088/14757516/2014/05/042.
Steigerwald, Heinrich, Marinoni, Christian, and Bel, Julien, Email: heinrich.steigerwald@cpt.univmrs.fr, Email: jbel@cpt.univmrs.fr, Email: christian.marinoni@cpt.univmrs.fr. Thu .
"Probing nonstandard gravity with the growth index: a background independent analysis". United States.
doi:10.1088/14757516/2014/05/042.
@article{osti_22373554,
title = {Probing nonstandard gravity with the growth index: a background independent analysis},
author = {Steigerwald, Heinrich and Marinoni, Christian and Bel, Julien, Email: heinrich.steigerwald@cpt.univmrs.fr, Email: jbel@cpt.univmrs.fr, Email: christian.marinoni@cpt.univmrs.fr},
abstractNote = {Measurements of the growth index of linear matter density fluctuations γ(z) provide a clue as to whether Einstein's field equations encompass gravity also on large cosmic scales, those where the expansion of the universe accelerates. We show that the information encoded in this function can be satisfactorily parameterized using a small set of coefficients γ{sub i}, in such a way that the true scaling of the growth index is recovered to better than 1% in most dark energy and dark gravity models. We find that the likelihood of current data, given this formalism and the Λ Cold Dark Matter (ΛCDM) expansion model of Planck, is maximal for γ{sub 0} = 0.74{sup +0.44}{sub −0.41} and γ{sub 1} = 0.01{sup +0.46}{sub −0.46}, a measurement compatible with the ΛCDM predictions (γ{sub 0} = 0.545, γ{sub 1} = −0.007). In addition, data tend to favor models predicting slightly less growth of structures than the Planck ΛCDM scenario. The main aim of the paper is to provide a prescription for routinely calculating, in an analytic way, the amplitude of the growth indices γ{sub i} in relevant cosmological scenarios, and to show that these parameters naturally define a space where predictions of alternative theories of gravity can be compared against growth data in a manner which is independent from the expansion history of the cosmological background. As the standard Ωplane provides a tool to identify different expansion histories H(t) and their relation to various cosmological models, the γplane can thus be used to locate different growth rate histories f(t) and their relation to alternatives model of gravity. As a result, we find that the DvaliGabadadzePorrati gravity model is rejected with a 95% confidence level. By simulating future data sets, such as those that a Euclidlike mission will provide, we also show how to tell apart ΛCDM predictions from those of more extreme possibilities, such as smooth dark energy models, clustering quintessence or parameterized postFriedmann cosmological models.},
doi = {10.1088/14757516/2014/05/042},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 05,
volume = 2014,
place = {United States},
year = {Thu May 01 00:00:00 EDT 2014},
month = {Thu May 01 00:00:00 EDT 2014}
}

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