Testing general relativity in cosmology

Abstract

We review recent developments and results in testing general relativity (GR) at cosmological scales. The subject has witnessed rapid growth during the last two decades with the aim of addressing the question of cosmic acceleration and the dark energy associated with it. However, with the advent of precision cosmology, it has also become a well-motivated endeavor by itself to test gravitational physics at cosmic scales. We overview cosmological probes of gravity, formalisms and parameterizations for testing deviations from GR at cosmological scales, selected modified gravity (MG) theories, gravitational screening mechanisms, and computer codes developed for these tests. We then provide summaries of recent cosmological constraints on MG parameters and selected MG models. We supplement these cosmological constraints with a summary of implications from the recent binary neutron star merger event. Next, we summarize some results on MG parameter forecasts with and without astrophysical systematics that will dominate the uncertainties. The review aims at providing an overall picture of the subject and an entry point to students and researchers interested in joining the field. It can also serve as a quick reference to recent results and constraints on testing gravity at cosmological scales.

Pole dark energy

“…Effectively, p ≫ 1 freezes the dynamics of σ. This is not dissimilar to screening mechanisms in modified gravity where Vainshtein screening (or k-mouflage) works by decoupling the field through a large kinetic term [13][14][15].…”

Tension of the EG statistic and redshift space distortion data with the Planck - ΛCDM model and implications for weakening gravity

“…The effects of MG [52][53][54][55][56][57][58][59][60][61] models are indistinguishable from GR at the geometric cosmological background level [26,62,63]. Signatures of MG can only be obtained by investigating the dynamics of cosmological perturbations [64,65] using specific statistics obtained through dynamical probe observables such as the two-point correlation of and power spectrum of the galaxy distribution, the RSD and WL. A useful bias free statistic is the f σ 8 product of the rate of growth of matter density perturbations f times σ 8 discussed in more detail in what follows.…”

Galileon scalar electrodynamics

“…can remove the higher-derivative terms that appear in Eq. (15). See Appendices (C) and (E), for details.…”

“…There is a resurgence of interest in higher-derivative theories primarily from the modifications of gravity in the short and long distances [10][11][12][13][14][15]. It is now known that higher derivative gravity theories like f (R) are degenerate, and do not suffer from Ostrogradsky instability [16].…”