Cosmological gravity on all scales: Simple equations, required conditions, and a framework for modified gravity

Abstract

This paper studies model independent modified gravity in cosmological settings. Using higher order equations from the post Friedmann approach to derive a single set of ``simple 1PF'' (first post Friedmann) equations, the author looks at both traditional limits of cosmological gravity, the large scales where relativistic perturbation theory works and at smaller nonlinear scales that are the domain of Newtonian gravity. Criteria are provided for deciding which modified gravity theories are amenable to the proposed approach and a rigorous underpinning to phenomenological N-body simulations is provided, with a view to utilizing all data gleaned from future surveys.

Topics & Concepts