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Paper   IPM / Astronomy / 13677
School of Astronomy
  Title:   Cosmological perturbations and structure formation in nonlocal infrared modifications of general relativity
1.  Y. Dirian
2.  S. Foffa
3.  N. Khosravi
4.  M. Kunz
5.  M. Maggiore
  Status:   Published
  Journal: JCAP
  Year:  2014
  Supported by:  IPM
We study the cosmological consequences of a recently proposed nonlocal modification of general relativity, obtained by adding a term m2R□−2R to the Einstein-Hilbert action. The model has the same number of parameters as ΛCDM, with mreplacing ΩΛ, and is very predictive. At the background level, after fixing m so as to reproduce the observed value of ΩM, we get a pure prediction for the equation of state of dark energy as a function of redshift, wDE(z), with wDE(0) in the range [−1.165,−1.135] as ΩM varies over the broad range ΩM∈[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

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