Cosmological constraints on parametrized interacting dark energy

TL;DR

This paper explores models of the universe with interacting dark energy and dark matter, using observational data to constrain the interaction and examining the implications for cosmological dynamics.

Contribution

It introduces a parametrized class of interacting dark sector models based on a function of the density ratio, linking them to unified dark fluid models, and constrains them with observational data.

Findings

Late Universe data suggest possible dark sector interaction.

Early Universe data strongly constrain the interaction, especially in models affecting background dynamics.

Certain models are consistent with observational constraints, indicating potential dark sector interactions.

Abstract

We reconsider the dynamics of the Universe in the presence of interactions in the cosmological dark sector. A class of interacting models is introduced via a real function $f\left(r\right)$ of the ratio $r$ between the energy densities of the (pressureless) cold dark matter (CDM) and dark energy (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 dark sector, 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 $f\left(r\right)$ we recover several models already studied in the literature. We analyse various special cases of this type of interacting models using a suitably modified version of the CLASS code combined with MontePython 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 oscilations (BAO) and data from the Planck satellite (Planck TT). Our analysis shows that even if data from the late Universe ($H_{0}$, SNe Ia and CC) indicate an interaction in the dark sector, the data related to the early Universe (BAO and Planck TT) constrain this interaction substantially, in particular for cases in which the background dynamics is strongly affected.