A Unified Approach to Cosmic Acceleration

TL;DR

This paper develops a comprehensive effective field theory framework for late-time cosmic acceleration, unifying various models and providing a basis for future observational constraints.

Contribution

It introduces the most general symmetry-based action for cosmic acceleration, unifies existing models, and extends the effective field theory approach to scalar-tensor and multi-field scenarios.

Findings

Reproduces existing late-time acceleration models as special cases.

Provides background and perturbation equations for the unified framework.

Lays groundwork for phenomenological constraints on model parameters.

Abstract

We present a unified framework for the study of late time cosmic acceleration. Using methods of effective field theory, we show that existing proposals for late time acceleration can be subsumed in a single framework, rather than many compartmentalized theories. We construct the most general action consistent with symmetry principles, derive the background and perturbation evolution equations, and demonstrate that for special choices of our parameters we can reproduce results already existing in the literature. Lastly, we lay the foundation for future work placing phenomenological constraints on the parameters of the effective theory. Although in this paper we focus on late time acceleration, our construction also generalizes the effective field theory of inflation to the scalar-tensor and multi-field case for perturbatively constructed backgrounds.