A novel early Dark Energy model

TL;DR

This paper introduces a new early dark energy model with a dynamic equation of state that evolves over cosmic time, fitting observational data and providing an alternative to the cosmological constant for explaining late-time acceleration.

Contribution

It proposes a novel EDE model with a redshift-dependent equation of state, constrained by observational data, offering a dynamic alternative to the cosmological constant.

Findings

The model fits supernova and CMB data well.

It predicts a non-negligible early dark energy contribution.

It provides an alternative explanation for late-time cosmic acceleration.

Abstract

We present a theoretical study of an early dark energy (EDE) model. The equation of state $\omega(z)$ evolves during the thermal history in a framework of a Friedmann-Lemaitre-Robertson-Walker Universe, following an effective parametrization that is a function of redshift $z$. We explore the evolution of the system from the radiation domination era to the late times, allowing the EDE model to have a non-negligible contribution at high redshift (as opposed to the cosmological constant that only plays a role once the structure is formed) with a very little input to the Big Bang Nucleosynthesis, and to do so, the equation of state mimics the radiation behaviour, but being subdominant in terms of its energy density. At late times, the equation of state of the dark energy model asymptotically tends to the fiducial value of the De Sitter domination epoch, providing an explanation for the accelerated expansion of the Universe at late times, emulating the effect of the cosmological constant. The proposed model has three free parameters, that we constrain using SNIa luminosity distances, along with the CMB shift parameter and the deceleration parameter calculated at the time of dark energy - matter equality. With full knowledge of the best fit for our model, we calculate different observables and compare these predictions with the standard$\Lambda$CDM model. Besides the general consent of the community with the cosmological constant, there is no fundamental reason to choose that particular candidate as dark energy. Here, we open the opportunity to consider a more dynamical model, that also accounts for the late accelerated expansion of the Universe.