A comparison of Einstein-Boltzmann solvers for testing General Relativity

TL;DR

This paper compares various Einstein-Boltzmann solvers across multiple gravity models, demonstrating their high agreement and confirming their suitability for precision cosmological tests of General Relativity.

Contribution

It provides a comprehensive comparison of multiple Einstein-Boltzmann codes for diverse gravity theories, establishing their accuracy for precision cosmology.

Findings

Codes agree at sub-percent level for CMB and matter power spectra

The suite of codes is suitable for precision tests of gravity

High consistency across models confirms reliability of these solvers

Abstract

We compare Einstein-Boltzmann solvers that include modifications to General Relativity and find that, for a wide range of models and parameters, they agree to a high level of precision. We look at three general purpose codes that primarily model general scalar-tensor theories, three codes that model Jordan-Brans-Dicke (JBD) gravity, a code that models f(R) gravity, a code that models covariant Galileons, a code that models Ho\v{r}ava-Lifschitz gravity and two codes that model non-local models of gravity. Comparing predictions of the angular power spectrum of the cosmic microwave background and the power spectrum of dark matter for a suite of different models, we find agreement at the sub-percent level. This means that this suite of Einstein-Boltzmann solvers is now sufficiently accurate for precision constraints on cosmological and gravitational parameters.