Notes on Ghost Dark Energy

TL;DR

This paper explores a phenomenological ghost dark energy model based on QCD principles, analyzing its cosmological implications, stability, and observational constraints, revealing potential instabilities and effects of dark energy-matter interaction.

Contribution

It introduces a ghost dark energy model linked to QCD, fits it with observational data, and investigates its stability and interaction with dark matter.

Findings

Universe approaches de Sitter phase at late times

Model fits observational data well

Dark energy may be unstable due to negative sound speed

Abstract

We study a phenomenological dark energy model which is rooted in the Veneziano ghost of QCD. In this dark energy model, the energy density of dark energy is proportional to Hubble parameter and the proportional coefficient is of the order $\Lambda^3_{QCD}$, where $\Lambda_{QCD}$ is the mass scale of QCD. The universe has a de Sitter phase at late time and begins to accelerate at redshift around $z_{acc}\sim0.6$. We also fit this model and give the constraints on model parameters, with current observational data including SnIa, BAO, CMB, BBN and Hubble parameter data. We find that the squared sound speed of the dark energy is negative, which may cause an instability. We also study the cosmological evolution of the dark energy with interaction with cold dark matter.