Dark sector interactions and the curvature of the Universe in light of Planck's 2018 data

TL;DR

This study examines interacting dark energy models using Planck 2018 data, revealing a preference for positive dark sector interaction and exploring the effects of spatial curvature and Hubble constant priors on cosmological parameters.

Contribution

It provides new constraints on dark sector interactions considering spatial curvature and Hubble priors, extending previous analyses with updated observational data.

Findings

Positive interaction parameter favored with $\alpha \\approx 0.2$

Non-zero curvature slightly preferred, relaxing parameter correlations

SH0ES prior significantly influences interacting dark energy model results

Abstract

We investigate the observational viability of a class of interacting dark energy (iDE) models in the light of the latest Cosmic Microwave Background (CMB), type Ia supernovae (SNe) and SH0ES Hubble parameter measurements. Our analysis explores the assumption of a non-zero spatial curvature, the correlation between the interaction parameter $\alpha$ and the current expansion rate $H_0$, and updates the results reported in \cite{micol}. Initially, assuming a spatially flat universe, the results show that the best-fit of our joint analysis clearly favours a positive interaction, i.e., an energy flux from dark matter to dark energy, with $\alpha \approx 0.2$, while the non-interacting case, $\alpha = 0$, is ruled out by more than $3\sigma$ confidence level. On the other hand, considering a non-zero spatial curvature, we find a slight preference for a negative value of the curvature parameter, which seems to relax the correlation between the parameters $\alpha$ and $H_0$, as well as between $H_0$ and the normalization of the matter power spectrum on scales of 8$h^{-1}$ Mpc ($\sigma_8$). Finally, we discuss the influence of considering the SH$0$ES prior on $H_0$ in the joint analyses, and find that such a choice does not change considerably the standard cosmology predictions but has a significant influence on the results of the iDE model.