Some cosmological features of 4D Gauss–Bonnet gravity with varying cosmological constant

Abstract

We explore some cosmological features of the newly suggested 4D Gauss–Bonnet gravity through two different models assuming a varying cosmological constant [Formula: see text]. Observational constraints, such as the cosmic transit and the flat curvature, have been considered in constructing the models. The cosmology in this work has been probed using a given scale factor derived from the desired cosmic behavior which is the inverse of the usual viewpoint. Several models for [Formula: see text] have been proposed in the literature; we use two different ansatze of varying [Formula: see text] and compare the obtained result. We have found that the second ansatz for the varying [Formula: see text], expressed in terms of the Hubble parameter H, gives better results than the first one. The sound speed causality condition along with all nonlinear energy conditions are satisfied for the case of [Formula: see text]. The cosmographic parameters have been investigated.