Effective field theory of cosmic acceleration: Constraining dark energy with CMB data

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 effective field theory and designer $f(R)$ models, both on $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ and $w\mathrm{CDM}$ background expansion histories, using data from Planck temperature and lensing potential spectra, WMAP low-$\ensuremath{\ell}$ polarization spectra (WP), and baryon acoustic oscillations (BAO). Upon inspecting the theoretical stability of the models on the given background, we find nontrivial 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 $w\mathrm{CDM}$ background case these viability priors could dominate the marginalized posterior distributions. Interestingly, with $\mathrm{Planck}+\mathrm{WP}+\mathrm{BAO}+\mathrm{lensing}$ data, in $f(R)$ gravity models, we get very strong constraints on the constant dark energy equation of state, ${w}_{0}\ensuremath{\in}(\ensuremath{-}1,\ensuremath{-}0.9997)$ (95% C.L.).