Effective Field Theory of Cosmic Acceleration: constraining dark energy with CMB data

TL;DR

This paper introduces and applies EFT-based modifications to cosmological codes to constrain dark energy models using Planck, WMAP, and BAO data, revealing tight bounds on $f(R)$ gravity and dark energy parameters.

Contribution

It presents publicly available EFTCAMB/EFTCosmoMC codes for analyzing dark energy models and demonstrates their use with observational data to derive constraints.

Findings

Strong constraints on $w_0$ in $f(R)$ models, $w_0 in (-1,-0.9997)$ at 95% C.L.

Viability priors significantly influence posterior distributions in $w$CDM models.

Data combination impacts the tightness of constraints on dark energy parameters.

Abstract

We introduce EFTCAMB/EFTCosmoMC as publicly available patches to the commonly used CAMB/CosmoMC codes. We briefly describe the structure of the codes, their applicability and main features. To illustrate the use of these patches, we obtain constraints on parametrized pure EFT and designer $f(R)$ models, both on $\Lambda$CDM and $w$CDM background expansion histories, using data from Planck temperature and lensing potential spectra, WMAP low-$\ell$ polarization spectra (WP), and baryon acoustic oscillation (BAO). Upon inspecting theoretical stability of the models on the given background, we find non-trivial parameter spaces that we translate into viability priors. We use different combinations of data sets to show their individual effects on cosmological and model parameters. Our data analysis results show that, depending on the adopted data sets, in the $w$CDM background case this viability priors could dominate the marginalized posterior distributions. Interestingly, with Planck+WP+BAO+lensing data, in $f(R)$ gravity models, we get very strong constraints on the constant dark energy equation of state, $w_0\in(-1,-0.9997)\,\,(95% {\rm C.L.})$.