Inferring dark energy properties from the scale factor parametrisation

Abstract

We propose and implement a novel test to assess deviations from well-established concordance $\Lambda$CDM cosmology while inferring dark energy properties. In contrast to the commonly implemented parametric forms of the dark energy equation-of-state (EoS), we test the validity of the cosmological constant on the more fundamental scale factor [$a(t)$] which determines the expansion rate of the Universe. We constrain our extended `general model' using the late-time observables. The posterior of the dark energy EoS is mainly constrained to be quintessence-like naturally excluding physically unviable regions such as phantom crossings or exponential growth.