Cosmological constraints on an exponential interaction in the dark sector

TL;DR

This paper investigates an exponential interaction between dark matter and dark energy in a flat universe, using observational data to constrain the model parameters, and finds that the interaction is very small and consistent with no interaction.

Contribution

It introduces and constrains an exponential interaction model between dark matter and dark energy, providing observational bounds and analyzing its distinguishability from the standard ΛCDM model.

Findings

The interaction parameter ξ is consistent with zero within observational uncertainties.

Both phantom and quintessence dark energy regimes are allowed, with w_x close to -1.

The interaction model is nearly indistinguishable from ΛCDM at the background level.

Abstract

Cosmological models where dark matter (DM) and dark energy (DE) interact with each other are the general scenarios in compared to the non-interacting models. The interaction is usually motivated from the phenomenological ground and thus there is no such rule to prefer a particular interaction between DM and DE. Being motivated, in this work, allowing an exponential interaction between DM and DE in a spatially flat homogeneous and isotropic universe, we explore the dynamics of the universe through the constraints of the free parameters where the strength of the interaction is characterized by the dimensionless coupling parameter $\xi$ and the equation of state (EoS) for DE, $w_x$, is supposed to be a constant. The interaction scenario is fitted using the latest available observational data. Our analyses report that the observational data permit a non-zero value of $\xi$ but it is very small and consistent with $\xi =0$. From the constraints on $w_x$, we find that both phantom ($w_x< -1$) and quintessence ($w_x> -1$) regimes are equally allowed but $w_x$ is very close to `$-1$'. The overall results indicate that at the background level, the interaction model cannot be distinguished from the base $\Lambda $-cold dark matter model while from the perturbative analyses, the interaction model mildly deviates from the base model. We highlight that, even if we allow DM and DE to interact in an exponential manner, but according to the observational data, the evidence for a non-zero coupling is very small.