Cosmological Implications of the Effective Field Theory of Cosmic Acceleration

TL;DR

This paper explores how the effective field theory of cosmic acceleration impacts the universe's expansion history and uses observational data to constrain the theory's parameters, highlighting discrepancies with certain models.

Contribution

It provides a comprehensive analysis of the background expansion constraints on the EFT of cosmic acceleration, including the effects of various scalar couplings and their observational implications.

Findings

Constraints on EFT parameters from supernovae, CMB, BAO data

Discrepancy between scalar EFT with Gauss-Bonnet coupling and observations

Implications for models of dark energy and modified gravity

Abstract

We consider cosmological constraints arising from the background expansion history on the ef- fective field theory of cosmic acceleration, a theoretical framework that allows for a unified way to classify both models of dark energy and modified gravity within the linear regime. In the Einstein frame, the most general action for the background can be written in terms of a canonical scalar field which is non-minimally coupled to matter. The leading corrections to the action are expressible through a quartic kinetic term, and scalar couplings to a Gauss-Bonnet curvature term and the Einstein tensor. We determine the implications of the terms in this general action for the predicted expansion history in the context of dynamical attractors. We find that each modifies the matter dominated and/or accelerative eras in ways that allow us to place cosmological constraints on them. We present current constraints on the effective action using the latest Type Ia supernovae, Cosmic Microwave Background, and Baryonic Acoustic Oscillation data. This includes finding that the scalar field EFT with a coupled Gauss-Bonnet term and the data are significantly discrepant.