paper

Cosmological perturbations and structure formation in nonlocal infrared modifications of general relativity

arXiv:1403.6068 · doi:10.1103/PhysRevD.90.023005

Abstract

We study the cosmological consequences of a recently proposed nonlocal modification of general relativity, obtained by adding a term to the Einstein-Hilbert action. The model has the same number of parameters as CDM, with replacing , and is very predictive. At the background level, after fixing so as to reproduce the observed value of , we get a pure prediction for the equation of state of dark energy as a function of redshift, , with in the range as varies over the broad range . We find that the cosmological perturbations are well-behaved, and the model fully fixes the dark energy perturbations as a function of redshift and wavenumber . 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 , to be compared with in CDM. For the Newtonian potential on subhorizon scales our results are well fitted by with a scale-independent and , while the anisotropic stress is negligibly small.

39 pages, 20 figures

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