Testing gravity with CAMB and CosmoMC

TL;DR

This paper presents a new patch for CAMB and CosmoMC that enables flexible modifications to cosmological perturbation equations, facilitating tests of gravity theories with observational data.

Contribution

The authors introduce an extended patch for CAMB and CosmoMC that supports general modifications of perturbation equations, surpassing previous limitations and incorporating recent parametrizations.

Findings

Constraints on neutrino mass from combined data

Limits on scalar-tensor gravity parameters

Demonstration of the patch's application to observational data

Abstract

We introduce a patch to the commonly used public codes CAMB and CosmoMC that allows the user to implement a general modification of the equations describing the growth of cosmological perturbations, while preserving the covariant conservation of the energy-momentum. This patch replaces the previously publicly released code MGCAMB, while also extending it in several ways. The new version removes the limitation of late-time-only modifications to the perturbed Einstein equations, and includes several parametrization introduced in the literature. To demonstrate the use of the patch, we obtain joint constraints on the neutrino mass and parameters of a scalar-tensor gravity model from CMB, SNe and ISW data as measured from the correlation of CMB with large scale structure.