Modified gravity versus shear viscosity: Imprints on the scalar matter perturbations
Abstract
Cosmological scalar perturbation theory studied in the Newtonian gauge depends on two potentials Φ and Ψ . In general relativity (GR), they must coincide (Φ =Ψ ) in the absence of anisotropic stresses sourced by the energymomentum tensor. On the other hand, it is widely accepted in the literature that potential deviations from GR can be parametrized by Φ ≠Ψ . The latter feature is therefore present in both GR cosmologies equipped with shear viscous fluids or modified gravity. We study the evolution of scalar matter density perturbations using the redshiftspacedistortionbased f (z )σ_{8}(z ) data as a tool to differentiate and characterize the imprints of both scenarios. We show that in the f (z )σ_{8}(z ) evolution both scenarios yield to completely different imprints in comparison to the standard cosmology. While the current available data are not sensitive to distinguish modified gravity from viscous shear cosmologies, future precise data can be used to break this indistinguishability.
 Publication:

Physical Review D
 Pub Date:
 December 2018
 DOI:
 10.1103/PhysRevD.98.123522
 arXiv:
 arXiv:1807.03357
 Bibcode:
 2018PhRvD..98l3522B
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology
 EPrint:
 10 pages, 6 figures. Matches PRD version