Instabilities in dark coupled models and constraints from cosmological data

TL;DR

This paper investigates instabilities in dark matter-dark energy interaction models and uses cosmological data to constrain these models, revealing potential for larger neutrino masses in coupled scenarios.

Contribution

It analyzes two parameterizations of dark sector interactions, identifies conditions for instabilities, and constrains viable models using cosmological data, highlighting implications for neutrino mass.

Findings

Coupled models with specific interactions can be stable under certain conditions.

Cosmological data allows for larger neutrino masses in coupled dark sector models.

Correlations between dark coupling and cosmological parameters are significant.

Abstract

Coupled dark matter-dark energy systems can suffer from non-adiabatic instabilities at early times and large scales. In these proceedings, we consider two parameterizations of the dark sector interaction. In the first one the energy-momentum transfer 4-vector is parallel to the dark matter 4-velocity and in the second one to the dark energy 4-velocity. In these cases, coupled models which suffer from non-adiabatic instabilities can be identified as a function of a generic coupling Q and of the dark energy equation of state. In our analysis, we do not refer to any particular cosmic field. We confront then a viable class of models in which the interaction is directly proportional to the dark energy density and to the Hubble rate parameter to recent cosmological data. In that framework, we show that correlations between the dark coupling and several cosmological parameters allow for a larger neutrino mass than in uncoupled models.