Comparison of Einstein-Boltzmann solvers for testing general relativity

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-BransDicke (JBD) gravity, a code that models fðRÞ gravity, a code that models covariant Galileons, a code that models Horava-Lifschitz gravity, and two codes that model nonlocal models of gravity. Comparing ˇ 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 subpercent level. This means that this suite of Einstein-Boltzmann solvers is now sufficiently accurate for precision constraints on cosmological and gravitational parameters.