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 Hubble function (OHD), Supernovae Type Ia (SNIa), baryon acoustic oscillations (BAO), and cosmic microwave background (CMB) observations, and we show that $\eta$ has a preference to a non-zero value, namely a deviation from $ \Lambda $CDM cosmology is favoured, although the zero value is marginally inside the 1$\sigma$ confidence level. However, we find that the present Hubble function value acquires a higher value, namely $H_0= 70.339^{+1.789}_{-1.761}$, which implies that the $H_0$ 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 to a de Sitter phase, since it exhibits a second transition from acceleration to deceleration. Finally, we perform statefinder and Om diagnostic analyses. The scenario behaves similarly to $ \Lambda$CDM paradigm at high redshifts, while the deviation becomes significant at late and recent times and especially in the future.