Dynamical dark sectors and neutrino masses and abundances

We investigate generalized interacting dark matter--dark energy scenarios with a time-dependent coupling parameter, allowing also for freedom in the neutrino sector. The models are tested in the phantom and quintessence regimes, characterized by equations of state, wₗ-1, respectively. Our analyses show that for some of the scenarios, the existing tensions on the Hubble constant H₀ and on the clustering parameter S₈ can be significantly alleviated. The relief is either due to (a) a dark energy component which lies within the phantom region or (b) the presence of a dynamical coupling in quintessence scenarios. The inclusion of massive neutrinos into the interaction schemes does not affect either the constraints on the cosmological parameters or the bounds on the total number or relativistic degrees of freedom N₄₅₅, which are found to be extremely robust and, in general, strongly consistent with the canonical prediction N₄₅₅=3. 045. The most stringent bound on the total neutrino mass M_ is M_<0. 116 eV and it is obtained within a quintessence scenario in which the matter mass-energy density is only mildly affected by the presence of a dynamical dark sector coupling.