We investigate the observational consequences of a novel class of stable interacting dark energy ( IDE ) models , featuring interactions between dark matter ( DM ) and dark energy ( DE ) .
In the first part of our work , we start by considering two IDE models which are known to present early-time linear perturbation instabilities .
Applying a transformation depending on the dark energy equation of state ( EoS ) to the DM-DE coupling , we then obtain two novel stable IDE models .
Subsequently , we derive robust and accurate constraints on the parameters of these models , assuming a constant EoS w _ { x } for the DE fluid , in light of some of the most recent publicly available cosmological data .
These include Cosmic Microwave Background ( CMB ) temperature and polarization anisotropy measurements from the Planck satellite , a selection of Baryon Acoustic Oscillation measurements , Supernovae Type-Ia luminosity distance measurements from the JLA sample , and measurements of the Hubble parameter up to redshift 2 from cosmic chronometers .
Our analysis displays a mild preference for the DE fluid residing in the phantom region ( w _ { x } < -1 ) , with significance up to 95 % confidence level , while we obtain new upper limits on the coupling parameter between the dark components .
The preference for a phantom DE suggests a coupling function Q < 0 , thus a scenario where energy flows from the DE to the DM .
We also examine the possibility of addressing the H _ { 0 } and \sigma _ { 8 } tensions , finding that only the former can be partially alleviated .
Finally , we perform a Bayesian model comparison analysis to quantify the possible preference for the two IDE models against the standard concordance \Lambda CDM model , finding that the latter is always preferred with the strength of the evidence ranging from positive to very strong .