On the dynamics of a dark sector coupling

Understand

Interacting dark energy models may play a crucial role in explaining several important observational issues in modern cosmology and also may provide a solution to current cosmological tensions.

• Since the phenomenology of the dark sector could be extremely rich, one should not restrict the interacting models to have a coupling parameter which is constant in cosmic time, rather allow for its dynamical behavior, as it is common practice in the literature when dealing with other dark energy properties, as the dark energy equation of state.
• We present here a compendium of the current cosmological constraints on a large variety of interacting models, investigating scenarios where the coupling parameter of the interaction function and the dark energy equation of state can be either constant or dynamical.
• For the most general schemes, in which both the coupling parameter of the interaction function and the dark energy equation of state are dynamical, we find $95\%$~CL evidence for a dark energy component at early times and slightly milder evidence for a dynamical dark coupling for the most complete observational data set exploited here, which includes CMB, BAO and Supernova Ia measurements.