A divergence-free parametrization for dynamical dark energy

TL;DR

This paper proposes a new divergence-free parametrization for dynamical dark energy, enabling more accurate observational constraints and suggesting a model slightly better fitting current data than the standard Lambda Cold Dark Matter model.

Contribution

It introduces a novel divergence-free parametrization of dark energy's equation of state that maintains consistency across cosmic history and systematically reduces to a Lambda-like model.

Findings

The new parametrization fits observational data slightly better than Lambda CDM.

It constrains dark energy to have an equation of state of -2/3 in the early universe and -1 today.

The model remains divergence-free throughout cosmic evolution.

Abstract

We introduce a new parametrization for the dark energy, led by the same idea to the linear expansion of the equation of state in scale factor $a$ and in redshift $z$, which diverges neither in the past nor future and contains the same number of degrees of freedom with the former two. We present constraints of the cosmological parameters using the most updated baryon acoustic oscillation (BAO) measurements along with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. This new parametrization allowed us to carry out successive observational analyses by decreasing its degrees of freedom systematically until ending up with a dynamical dark energy model that has the same number of parameters with $\Lambda$CDM. We found that the dark energy source with a dynamical equation of state parameter equal $-2/3$ at the early universe and $-1$ today fits the data slightly better than $\Lambda$.