Parametrizations for tests of gravity

TL;DR

This paper reviews various parametrization frameworks designed to systematically test gravity across different astrophysical and cosmological regimes, aiming for a unified approach to evaluate deviations from General Relativity.

Contribution

It provides a comprehensive overview of existing formalisms for testing gravity, highlighting their connections and outlining steps toward a unified framework.

Findings

Survey of multiple parametrization formalisms

Connections between different approaches are identified

Outlook on developing a unified testing framework

Abstract

With the increasing wealth of high-quality astronomical and cosmological data and the manifold departures from General Relativity in principle conceivable, the development of generalized parametrization frameworks that unify gravitational models and cover a wide range of length scales and a variety of observational probes to enable systematic high-precision tests of gravity has been a stimulus for intensive research. A review is presented here for some of the formalisms devised for this purpose, covering the cosmological large- and small-scale structures, the astronomical static weak-field regime as well as emission and propagation effects for gravitational waves. This includes linear and nonlinear parametrized post-Friedmannian frameworks, effective field theory approaches, the parametrized post-Newtonian expansion, the parametrized post-Einsteinian formalism as well as an inspiral-merger-ringdown waveform model among others. Connections between the different formalisms are highlighted where they have been established and a brief outlook is provided for general steps towards a unified global framework for tests of gravity and dark sector models.