Constraints on dark energy and modified gravity from the BOSS Full-Shape and DESI BAO data

TL;DR

This paper uses combined galaxy power spectrum, CMB, and BAO data to constrain dark energy and modified gravity parameters, demonstrating that large-scale structure data significantly improves bounds on certain parameters, with implications for future surveys.

Contribution

The study introduces a comprehensive analysis framework combining full-shape galaxy power spectrum with CMB and BAO data to constrain dark energy and modified gravity parameters.

Findings

CMB data is most sensitive to the braiding parameter $oldsymbol{eta}$.

Adding large-scale structure data tightens bounds on $oldsymbol{eta}$ and the dark energy equation of state.

BAO data helps break degeneracies, improving parameter constraints.

Abstract

We constrain dark energy and modified gravity within the effective field theory of dark energy framework using the full-shape BOSS galaxy power spectrum, combined with Planck cosmic microwave background (CMB) data and recent baryon acoustic oscillations (BAO) measurements from DESI. Specifically, we focus on a varying braiding parameter $\alpha_{\rm B}$, a running of the ``effective'' Planck mass $\alpha_{\rm M}$, and a constant dark energy equation of state $w$. The analysis is performed with two of these parameters at a time, including all the other standard cosmological parameters and marginalizing over bias and nuisance parameters. The full-shape galaxy power spectrum is modeled using the effective field theory of large-scale structure up to 1-loop order in perturbation theory. We find that the CMB data is most sensitive to $\alpha_{\rm B}$, and that adding large-scale structure information only slightly changes the parameter constraints. However, the large-scale structure data significantly improve the bounds on $\alpha_{\rm M}$ and $w$ by a factor of two. This improvement is driven by background information contained in the BAO, which breaks the degeneracy with $H_0$ in the CMB. We confirm this by comparing the BOSS full-shape information with BOSS BAO, finding no significant differences. This is likely to change with future high-precision full-shape data from Euclid and DESI however, to which the pipeline developed here is immediately applicable.