Observational constraints on one-parameter dynamical dark-energy parametrizations and the $H_0$ tension

TL;DR

This study evaluates five one-parameter dark energy models against multiple cosmological datasets, finding they favor phantom dark energy and help alleviate the H_0 tension, with Bayesian analysis showing competitive fit compared to Lambda CDM.

Contribution

It provides a comprehensive observational analysis of one-parameter dark energy models, highlighting their potential to address the H_0 tension and their comparable performance to two-parameter models.

Findings

All models favor a phantom dark energy equation of state.

Models yield H_0 values consistent with direct measurements.

One-parameter models fit data as well as or better than two-parameter models.

Abstract

The phenomenological parametrizations of dark-energy (DE) equation of state can be very helpful, since they allow for the investigation of its cosmological behavior despite the fact that its underlying theory is unknown. However, although there has been a large amount of research on DE parametrizations which involve two or more free parameters, the one-parameter parametrizations seem to be underestimated. We perform a detailed observational confrontation of five one-parameter DE models, with observational data from cosmic microwave background (CMB), Joint light-curve analysis sample from Supernovae Type Ia observations (JLA), baryon acoustic oscillations (BAO) distance measurements, and cosmic chronometers (CC). We find that all models favor a phantom DE equation of state at present time, while they lead to $H_0$ values in perfect agreement with its direct measurements and therefore they offer an alleviation to the $H_0$-tension. Finally, performing a Bayesian analysis we show that although $\Lambda$CDM cosmology is still favored, one-parameter DE models have similar or better efficiency in fitting the data comparing to two-parameter DE parametrizations, and thus they deserve a thorough investigation.