Thermal evolution and stability analysis of phenomenologically emergent dark energy model

TL;DR

This paper investigates the thermal evolution and stability of the phenomenologically emergent dark energy (PEDE) model, revealing its unusual future behaviour, phantom nature, and potential instability through dynamical and stability analyses.

Contribution

It provides a detailed analysis of the PEDE model's cosmic evolution, stability, and thermodynamic properties, highlighting its differences from standard cosmology and potential issues in the future.

Findings

PEDE model exhibits unusual future behaviour in Hubble and deceleration parameters

The model's phantom nature leads to null energy condition violation

Asymptotic future of the model appears unstable based on stability analyses

Abstract

The phenomenologically emergent dark energy (PEDE) model is a varying dark energy model with no extra degrees of freedom proposed by Li and Shafieloo\citep{Li_2019} to alleviate the Hubble tension. The statistical consistency of the model has been discussed by many authors. Since the model depicts a phantom dark energy that increases with redshift, its cosmic evolution, particularly during the late phase, must be examined. We discover that the model's Hubble and deceleration parameters display unusual behaviour in the future, which differs from $\Lambda$CDM cosmology. We find the model also follows a distinct evolution in the statefinder plane. The phantom nature of the model leads to the violation of the null energy condition and a decrease in horizon entropy. The asymptotic future epoch also seems to be unstable based on our dynamical system analysis as well as the stability analysis based on dark energy sound speed.