Cosmological tests of gravity with latest observations

TL;DR

This paper tests modified gravity theories on cosmological scales using the latest observational data, finding deviations from general relativity at over 3 sigma, suggesting potential new physics or systematic effects.

Contribution

It provides the first comprehensive analysis combining multiple cosmological observations to test deviations from general relativity in the effective Newton's constant and gravitational slip.

Findings

Deviations from GR at 3.1 sigma in a two-parameter model.

Deviations increase to 3.7 sigma with a general parametrisation.

Potential indication of new physics or observational systematics.

Abstract

We perform observational tests of modified gravity on cosmological scales following model-dependent and model-independent approaches using the latest astronomical observations, including measurements of the local Hubble constant, cosmic microwave background, the baryonic acoustic oscillations and redshift space distortions derived from galaxy surveys including the SDSS BOSS and eBOSS, as well as the weak lensing observations performed by the CFHTLenS team. Using all data combined, we find a deviation from the prediction of general relativity in both the effective Newton's constant, $\mu(a,k)$, and in the gravitational slip, $\eta(a,k)$. The deviation is at a $3.1\sigma$ level in the joint $\{\mu(a,k),\eta(a,k)\}$ space using a two-parameter phenomenological model for $\mu$ and $\eta$, and it reaches a $3.7\sigma$ level if a general parametrisation is used. This signal, which may be subject to unknown observational systematics, or a sign of new physics, is worth further investigating with forthcoming observations.