Cosmological constraints on parametrized interacting dark energy

Abstract We reconsider the dynamics of the Universe in the presence of interactions in the cosmological darksector. A class of interacting modelsis introduced via a real function f r of the ratio r between the energy densities of the (pressureless) cold dark matter(CDM) and darkenergy (DE). The subclass of models for which the ratio r depends only on the scale factor is shown to be equivalent to unified models of the darksector, i.e. models for which the CDM and DE components can be combined in order to form a unified dark fluid. For specific choices of the function f r we recover several models already studied in the literature. We analyze various special cases of this type of interacting modelsusing a suitably modified version of the CLASS code combined with Monte Python in order to constrain the parameter space with the data from supernova of type SNe Ia (JLA), the Hubble constant H 0 , cosmic chronometers (CC), baryon acoustic oscillations(BAO) and data from the Plancksatellite ( PlanckTT). Our analysis shows that even if data from the late Universe ( H 0 , SNe Ia and CC) indicate an interaction in the darksector, the data related to the early Universe (BAO and PlanckTT) constrain this interaction substantially, in particular for cases in which the background dynamics is strongly affected.