Tensions in the dark: shedding light on Dark Matter-Dark Energy interactions

Abstract

The emergence of an increasingly strong tension between the Hubble rate inferred from early- and late-time observations has reinvigorated interest in nonstandard scenarios, with the aim of reconciling these measurements. One such model involves interactions between Dark Matter and Dark Energy. Here we consider a specific form of the coupling between these two fluids proportional to the Dark Energy energy density, which has been studied extensively in the literature and claimed to substantially alleviate the Hubble tension. We complement the work already discussed in several previous analyses and show that, once all relevant cosmological probes are included simultaneously, the value of the Hubble parameter in this model is $H_0=69.82_{-0.76}^{+0.63}$ km/(s Mpc), which reduces the Hubble tension to $2.5\sigma$. Furthermore, we also perform a statistical model comparison, finding a $\Delta\chi^2$ of $-2.15$ (corresponding to a significance of 1.5$\sigma$) with the inclusion of one additional free parameter, showing no clear preference for this model with respect to $\Lambda$CDM, which is further confirmed with an analysis of the Bayes ratio.