Instabilities in dark coupled models and constraints from cosmological data

Understand

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.