Modified gravity: the CMB, weak lensing and general parameterisations

Thomas, Shaun A.; Appleby, Stephen A.; Weller, Jochen

doi:10.1088/1475-7516/2011/03/036

Title: Modified gravity: the CMB, weak lensing and general parameterisations

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Abstract

We examine general physical parameterisations for viable gravitational models in the f(R) framework. This is related to the mass of an additional scalar field, called the scalaron, that is introduced by the theories. Using a simple parameterisation for the scalaron mass M(a) we show there is an exact correspondence between the model and popular parameterisations of the modified Poisson equation μ(a,k) and the ratio of the Newtonian potentials η(a,k). We argue that although f(R) models are well described by the general [μ(a,k),η(a,k)] parameterization, specific functional forms of μ,η in the literature do not accurately represent f(R) behaviour, specifically at low redshift. We subsequently construct an improved description for the scalaron mass (and therefore μ(a,k) and η(a,k)) which captures their essential features and has benefits derived from a more physical origin. We study the scalaron's observational signatures and show the modification to the background Friedmann equation and CMB power spectrum to be small. We also investigate its effects in the linear and non linear matter power spectrum-where the signatures are evident-thus giving particular importance to weak lensing as a probe of these models. Using this new form, we demonstrate how the next generation Euclid survey will constrain these theories and itsmore »« less

Authors:

Thomas, Shaun A. ^[1]; Appleby, Stephen A.; Weller, Jochen ^[2]

Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT (United Kingdom)
Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching (Germany)

Publication Date:: Tue Mar 01 00:00:00 EST 2011

OSTI Identifier:: 22275331

Resource Type:: Journal Article

Journal Name:: Journal of Cosmology and Astroparticle Physics

Additional Journal Information:: Journal Volume: 2011; Journal Issue: 03; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; COSMOLOGY; ENERGY SPECTRA; FIELD EQUATIONS; GRAVITATION; MASS; NONLINEAR PROBLEMS; POISSON EQUATION; POTENTIALS; PROBES; RED SHIFT; RELICT RADIATION; SCALAR FIELDS; SOLAR SYSTEM

Citation Formats


                    Thomas, Shaun A., Appleby, Stephen A., and Weller, Jochen. Modified gravity: the CMB, weak lensing and general parameterisations.  United States: N. p., 2011. 
        Web.  doi:10.1088/1475-7516/2011/03/036.

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                    Thomas, Shaun A., Appleby, Stephen A., & Weller, Jochen. Modified gravity: the CMB, weak lensing and general parameterisations.  United States.  https://doi.org/10.1088/1475-7516/2011/03/036

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                    Thomas, Shaun A., Appleby, Stephen A., and Weller, Jochen. 2011.  
        "Modified gravity: the CMB, weak lensing and general parameterisations".  United States.  https://doi.org/10.1088/1475-7516/2011/03/036.

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@article{osti_22275331,

  title        = {Modified gravity: the CMB, weak lensing and general parameterisations},

  author       = {Thomas, Shaun A. and Appleby, Stephen A. and Weller, Jochen},

  abstractNote = {We examine general physical parameterisations for viable gravitational models in the f(R) framework. This is related to the mass of an additional scalar field, called the scalaron, that is introduced by the theories. Using a simple parameterisation for the scalaron mass M(a) we show there is an exact correspondence between the model and popular parameterisations of the modified Poisson equation μ(a,k) and the ratio of the Newtonian potentials η(a,k). We argue that although f(R) models are well described by the general [μ(a,k),η(a,k)] parameterization, specific functional forms of μ,η in the literature do not accurately represent f(R) behaviour, specifically at low redshift. We subsequently construct an improved description for the scalaron mass (and therefore μ(a,k) and η(a,k)) which captures their essential features and has benefits derived from a more physical origin. We study the scalaron's observational signatures and show the modification to the background Friedmann equation and CMB power spectrum to be small. We also investigate its effects in the linear and non linear matter power spectrum-where the signatures are evident-thus giving particular importance to weak lensing as a probe of these models. Using this new form, we demonstrate how the next generation Euclid survey will constrain these theories and its complementarity to current solar system tests. In the most optimistic case Euclid, together with a Planck prior, can constrain a fiducial scalaron mass M{sub 0} = 9.4 × 10{sup −30}eV at the ∼ 20% level. However, the decay rate of the scalaron mass, with fiducial value ν = 1.5, can be constrained to ∼ 3% uncertainty.},

  doi          = {10.1088/1475-7516/2011/03/036},

  url          = {https://www.osti.gov/biblio/22275331},
  journal      = {Journal of Cosmology and Astroparticle Physics},

  issn         = {1475-7516},

  number       = 03,

  volume       = 2011,

  place        = {United States},

  year         = {Tue Mar 01 00:00:00 EST 2011},

  month        = {Tue Mar 01 00:00:00 EST 2011}

}

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