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

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.