Cosmological perturbations and structure formation in nonlocal infrared modifications of general relativity
- Département de Physique Théorique and Center for Astroparticle Physics, Université de Genève, 24 quai Ansermet, CH-1211 Genève 4 (Switzerland)
- School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)
We study the cosmological consequences of a recently proposed nonlocal modification of general relativity, obtained by adding a term m{sup 2}R □{sup −2}R to the Einstein-Hilbert action. The model has the same number of parameters as ΛCDM, with m replacing Ω{sub Λ}. At the background level, after fixing m so to reproduce the observed value of Ω{sub M}, we get a pure prediction for the equation of state of dark energy as a function of redshift, w{sub DE}(z), with w{sub DE}(0) in the range [−1.165,−1.135] as Ω{sub M} varies over the broad range Ω{sub M} element of [0.20,0.36]. We find that the cosmological perturbations are well-behaved, and the model fully fixes the dark energy perturbations as a function of redshift z and wavenumber k. The nonlocal model provides a good fit to supernova data and predicts deviations from General Relativity in structure formation and in weak lensing at the level of 3-4%, therefore consistent with existing data but readily detectable by future surveys. For the logarithmic growth factor we obtain γ ≅ 0.53, to be compared with γ ≅ 0.55 in ΛCDM. For the Newtonian potential on subhorizon scales our results are well fitted by Ψ(a;k) = [1+μ{sub s}a{sup s}]Ψ{sub GR}(a;k) with a scale-independent μ{sub s} ≅ 0.09 and s ≅ 2, while the anisotropic stress is negligibly small.
- OSTI ID:
- 22373515
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2014, Issue 06; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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