Updated observational constraints on spatially-flat and non-flat $\Lambda$CDM and XCDM cosmological models

TL;DR

This paper updates observational constraints on various flat and non-flat $ ext{Lambda}$CDM and XCDM cosmological models using Planck 2018 data and other cosmological observations, finding mild preferences for open geometry and quintessence-like dark energy.

Contribution

It provides the most restrictive constraints to date on cosmological parameters for flat LCDM and other models, incorporating multiple data sets and primordial power spectra.

Findings

Planck data favor closed geometry and phantom-like dark energy.

Non-CMB data favor open geometry and quintessence-like dark energy.

Joint analysis shows weak evidence for open geometry and moderate evidence for quintessence-like dark energy.

Abstract

We study 6 LCDM models, with 4 allowing for non-flat geometry and 3 allowing for a non-unity lensing consistency parameter $A_L$. We also study 6 XCDM models with a dynamical dark energy density X-fluid with equation of state $w$. For the non-flat models we use two different primordial power spectra, Planck $P(q)$ and new $P(q)$. These models are tested against: Planck 2018 CMB power spectra (P18) and lensing potential power spectrum (lensing), and an updated compilation of BAO, SNIa, $H(z)$, and $f\sigma_8$ data [non-CMB data]. P18 data favor closed geometry for the LCDM and XCDM models and $w<-1$ (phantom-like dark energy) for the XCDM models while non-CMB data favor open geometry for the LCDM models and closed geometry and $w>-1$ (quintessence-like dark energy) for the XCDM models. When P18 and non-CMB data are jointly analyzed there is weak evidence for open geometry and moderate evidence for quintessence-like dark energy. Regardless of data used, $A_L>1$ is always favored. The XCDM model constraints obtained from CMB data and from non-CMB data are incompatible, ruling out the 3 $A_L = 1$ XCDM models at $> 3\sigma$. In the 9 models not ruled out, for the P18+lensing+non-CMB data set we find little deviation from flat geometry and moderate deviation from $w=-1$. In all 6 non-flat models (not ruled out), open geometry is mildly favored, and in all 3 XCDM+$A_L$ models (not ruled out) quintessence-like dark energy is moderately favored (by at most $1.6 \sigma$). In the $A_L = 1$ non-flat LCDM cases, we find for P18+lensing+non-CMB data $\Omega_k = 0.0009 \pm 0.0017$ [$0.0008 \pm 0.0017$] for the Planck [new] $P(q)$ model, favoring open geometry. The flat LCDM model remains the simplest (largely) observationally-consistent cosmological model. Our cosmological parameter constraints obtained for the flat LCDM model (and other models) are the most restrictive results to date (Abridged).