Testing General Relativity in Cosmology

TL;DR

This review paper discusses recent progress in testing general relativity at cosmological scales, covering theoretical frameworks, observational constraints, and implications from recent astrophysical events, to evaluate gravity's validity in explaining cosmic acceleration.

Contribution

It provides a comprehensive overview of methods, theories, and recent constraints on modified gravity models, serving as a reference for researchers in the field.

Findings

Cosmological data constrain deviations from GR within current measurement uncertainties.

Recent binary neutron star merger observations impact constraints on gravity theories.

Forecasts indicate future tests will improve bounds on modified gravity parameters.

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.