Interacting dark energy with time varying equation of state and the $H_0$ tension

TL;DR

This paper investigates an interacting dark energy model with a time-varying equation of state, demonstrating it can alleviate the H0 tension and suggests a phantom behavior, though ΛCDM remains statistically favored.

Contribution

It introduces a specific interaction that removes stability issues at w_x = -1 and tests a dynamical dark energy model against observational data.

Findings

Interaction can resolve H0 tension.

Dark energy may exhibit phantom behavior.

ΛCDM remains statistically preferred.

Abstract

Almost in all interacting dark energy models present in the literature, the stability of the model becomes potentially sensitive to the dark energy equation of state parameter $w_x$, and a singularity arises at `$w_x = -1$'. Thus, it becomes mandatory to test the stability of the model into two separate regions, namely, for quintessence and phantom. This essentially brings in a discontinuity into the parameters space for $w_x$. Such discontinuity can be removed with some specific choices of the interaction or coupling function. In the present work we choose one particular coupling between dark matter and dark energy which can successfully remove such instability and we allow a dynamical dark energy equation of state parameter instead of the constant one. In particular, considering a dynamical dark energy equation of state with only one free parameter $w_0$, representing the current value of the dark energy equation of state, we confront the interacting scenario with several observational datasets. The results show that the present cosmological data allow an interaction in the dark sector, in agreement with some latest claims by several authors, and additionally, a phantom behaviour in the dark energy equation of state is suggested at present. Moreover, for this case the tension on $H_0$ is clearly released. As a final remark, we mention that according to the Bayesian analysis, $\Lambda$-cold dark matter ($\Lambda$CDM) is always favored over this interacting dark energy model.