A cosmological exclusion plot: towards modelindependent constraints on modified gravity from current and future growth rate data
Abstract
Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution was standard ΛCDM in the past and that the present matter density and power spectrum normalization are the same as in a ΛCDM model. Here we examine how the constraints change when these assumptions are lifted. We focus in particular on the parameter Y (also called G{sub eff}) that quantifies the deviation from the Poisson equation. This parameter can be estimated by comparing with the modelindependent growth rate quantity fσ{sub 8}(z) obtained through redshift distortions. We reduce the model dependency in evaluating Y by marginalizing over σ{sub 8} and over the initial conditions, and by absorbing the degenerate parameter Ω{sub m,0} into Y. We use all currently available values of fσ{sub 8}(z). We find that the combination Ycircumflex =YΩ{sub m,0}, assumed constant in the observed redshift range, can be constrained only very weakly by current data, Ycircumflex =0.28{sub −0.23}{sup +0.35} at 68% c.l. We also forecast the precision of a future estimation of Ycircumflex in a Euclidlike redshift survey. We find that the future constraints will reduce substantially the uncertainty, Ycircumflex =0.30{sub −0.09}{sup +0.08} , at 68% c.l., but the relative error on Ycircumflex around the fiducialmore »
 Authors:
 Dipartimento di Fisica e Scienze della Terra, Università di Parma, Viale Usberti 7/A, Parma, I43100 Italy (Italy)
 Institut fuer Theoretische Physik, RuprechtKarlsUniversitaet Heidelberg, Philosophenweg 16, Heidelberg, 69120 Germany (Germany)
 Publication Date:
 OSTI Identifier:
 22382004
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2015; Journal Issue: 02; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; DENSITY; ERRORS; GALACTIC EVOLUTION; GALAXIES; GRAVITATION; LIMITING VALUES; MATTER; POISSON EQUATION; RED SHIFT; SPECTRA
Citation Formats
Taddei, Laura, and Amendola, Luca, Email: laura.taddei@fis.unipr.it, Email: l.amendola@thphys.uniheidelberg.de. A cosmological exclusion plot: towards modelindependent constraints on modified gravity from current and future growth rate data. United States: N. p., 2015.
Web. doi:10.1088/14757516/2015/02/001.
Taddei, Laura, & Amendola, Luca, Email: laura.taddei@fis.unipr.it, Email: l.amendola@thphys.uniheidelberg.de. A cosmological exclusion plot: towards modelindependent constraints on modified gravity from current and future growth rate data. United States. doi:10.1088/14757516/2015/02/001.
Taddei, Laura, and Amendola, Luca, Email: laura.taddei@fis.unipr.it, Email: l.amendola@thphys.uniheidelberg.de. Sun .
"A cosmological exclusion plot: towards modelindependent constraints on modified gravity from current and future growth rate data". United States.
doi:10.1088/14757516/2015/02/001.
@article{osti_22382004,
title = {A cosmological exclusion plot: towards modelindependent constraints on modified gravity from current and future growth rate data},
author = {Taddei, Laura and Amendola, Luca, Email: laura.taddei@fis.unipr.it, Email: l.amendola@thphys.uniheidelberg.de},
abstractNote = {Most cosmological constraints on modified gravity are obtained assuming that the cosmic evolution was standard ΛCDM in the past and that the present matter density and power spectrum normalization are the same as in a ΛCDM model. Here we examine how the constraints change when these assumptions are lifted. We focus in particular on the parameter Y (also called G{sub eff}) that quantifies the deviation from the Poisson equation. This parameter can be estimated by comparing with the modelindependent growth rate quantity fσ{sub 8}(z) obtained through redshift distortions. We reduce the model dependency in evaluating Y by marginalizing over σ{sub 8} and over the initial conditions, and by absorbing the degenerate parameter Ω{sub m,0} into Y. We use all currently available values of fσ{sub 8}(z). We find that the combination Ycircumflex =YΩ{sub m,0}, assumed constant in the observed redshift range, can be constrained only very weakly by current data, Ycircumflex =0.28{sub −0.23}{sup +0.35} at 68% c.l. We also forecast the precision of a future estimation of Ycircumflex in a Euclidlike redshift survey. We find that the future constraints will reduce substantially the uncertainty, Ycircumflex =0.30{sub −0.09}{sup +0.08} , at 68% c.l., but the relative error on Ycircumflex around the fiducial remains quite high, of the order of 30%. The main reason for these weak constraints is that Ycircumflex is strongly degenerate with the initial conditions, so that large or small values of Ycircumflex are compensated by choosing nonstandard initial values of the derivative of the matter density contrast. Finally, we produce a forecast of a cosmological exclusion plot on the Yukawa strength and range parameters, which complements similar plots on laboratory scales but explores scales and epochs reachable only with largescale galaxy surveys. We find that future data can constrain the Yukawa strength to within 3% of the Newtonian one if the range is around a few Megaparsecs. In the particular case of f(R) models, we find that the Yukawa range will be constrained to be larger than 80 Mpc/h or smaller than 2 Mpc/h (95% c.l.), regardless of the specific f(R) model.},
doi = {10.1088/14757516/2015/02/001},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 02,
volume = 2015,
place = {United States},
year = {Sun Feb 01 00:00:00 EST 2015},
month = {Sun Feb 01 00:00:00 EST 2015}
}

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