New Parametrization of the Dark-Energy Equation of State with a Single Parameter

We propose a novel dark-energy equation-of-state parametrization, with a single parameter eta that quantifies the deviation from Lambda CDM cosmology. We first confront the scenario with various datasets, from the Hubble function (OHD), Pantheon, baryon acoustic oscillations (BAO), and their joint observations, and we show that eta has a preference for a non-zero value, namely, a deviation from Lambda CDM cosmology is favored, although the zero value is marginally inside the 1 sigma confidence level. However, we find that the present Hubble function value acquires a higher value, namely, H0=66.624-0.013+0.011 Km s-1 Mpc-1, which implies that the H0 tension can be partially alleviated. Additionally, we perform a cosmographic analysis, showing that the universe transits from deceleration to acceleration in the recent cosmological past; nevertheless, in the future, it will not result in a de Sitter phase since it exhibits a second transition from acceleration to deceleration. Finally, we perform the statefinder analysis. The scenario behaves similarly to the Lambda CDM paradigm at high redshifts, while the deviation becomes significant at late and recent times and especially in the future.