Parametrized frameworks for modified gravity are potentially useful tools for model-independent tests of general relativity on cosmological scales. The toy model of an Einstein–de Sitter universe provides a safe test bed in which to improve our understanding of their behavior. We implement a mathematically consistent parametrization at the level of the field equations, and use this to calculate the evolution of perturbations in an Einstein–de Sitter scenario. Our parametrization explicitly allows for new scalar degrees of freedom, and we compare this to theories in which the only degrees of freedom come from the metric and ordinary matter. The impact on the integrated Sachs-Wolfe effect and canonically conserved superhorizon perturbations is considered.

• Received 24 November 2011

DOI:https://doi.org/10.1103/PhysRevD.85.044020