A new interacting two fluid model and its consequences

TL;DR

This paper investigates interacting models of dark matter and dark energy in a homogeneous universe, deriving analytical solutions and constraining parameters with current observations, revealing a small interaction and potential phantom behavior.

Contribution

It introduces and analyzes a new interacting two-fluid dark sector model with both constant and variable dark energy equations of state, supported by observational data.

Findings

Small but nonzero dark sector interaction is favored.

Dark energy EoS can cross the phantom divide line.

Models are very close to the standard ΛCDM cosmology.

Abstract

In the background of a homogeneous and isotropic spacetime with zero spatial curvature, we consider interacting scenarios between two barotropic fluids, one is the pressureless dark matter (DM) and the other one is dark energy (DE), in which the equation of state (EoS) in DE is either constant or time dependent. In particular, for constant EoS in DE, we show that the evolution equations for both fluids can be analytically solved. For all these scenarios, the model parameters have been constrained using the current astronomical observations from Type Ia Supernovae, Hubble parameter measurements, and baryon acoustic oscillations distance measurements. Our analysis shows that both for constant and variable EoS in DE, a very small but nonzero interaction in the dark sector is favored while the EoS in DE can predict a slight phantom nature, i.e. the EoS in DE can cross the phantom divide line `$-1$'. On the other hand, although the models with variable EoS describe the observations better, but the Akaike Information Criterion supports models with minimal number of parameters. However, it is found that all the models are very close to the $\Lambda$CDM cosmology.