Minimal parameterizations for modified gravity

Understand

The increasing precision of cosmological data provides us with an opportunity to test general relativity (GR) on the largest accessible scales.

• Parameterizing modified gravity models facilitates the systematic testing of the predictions of GR, and gives a framework for detecting possible deviations from it.
• Several different parameterizations have already been suggested, some linked to classifications of theories, and others more empirically motivated.
• Here we describe a particular new approach which casts modifications to gravity through two free functions of time and scale, which are directly linked to the field equations, but also easy to confront with observational data.