The galaxy power spectrum take on spatial curvature and cosmic concordance

TL;DR

This paper uses full-shape galaxy power spectrum data to constrain the Universe's spatial curvature, finding it to be flat within sub-percent precision and highlighting the importance of such measurements in cosmology.

Contribution

It introduces the use of full-shape galaxy power spectrum measurements to break degeneracies and constrain spatial curvature, providing results consistent with a flat universe.

Findings

Constrained spatial curvature to Omega_K=0.0023 ± 0.0028.

Found consistency with a flat universe within sub-percent precision.

Identified tension between Planck and galaxy power spectrum data under curved universe assumptions.

Abstract

The concordance of the $\Lambda$CDM cosmological model in light of current observations has been the subject of an intense debate in recent months. The 2018 Planck Cosmic Microwave Background (CMB) temperature anisotropy power spectrum measurements appear at face value to favour a spatially closed Universe with curvature parameter $\Omega_K<0$. This preference disappears if Baryon Acoustic Oscillation (BAO) measurements are combined with Planck data to break the geometrical degeneracy, although the reliability of this combination has been questioned due to the strong tension present between the two datasets when assuming a curved Universe. Here, we approach this issue from yet another point of view, using measurements of the full-shape (FS) galaxy power spectrum, $P(k)$, from the Baryon Oscillation Spectroscopic Survey DR12 CMASS sample. By combining Planck data with FS measurements, we break the geometrical degeneracy and find $\Omega_K=0.0023 \pm 0.0028$. This constrains the Universe to be spatially flat to sub-percent precision, in excellent agreement with results obtained using BAO measurements. However, as with BAO, the overall increase in the best-fit $\chi^2$ suggests a similar level of tension between Planck and $P(k)$ under the assumption of a curved Universe. While the debate on spatial curvature and the concordance between cosmological datasets remains open, our results provide new perspectives on the issue, highlighting the crucial role of FS measurements in the era of precision cosmology.