Abstract
We explore some cosmological features of the newly suggested 4D Gauss-Bonnet gravity through two different models assuming a varying cosmological constant Lambda(t). 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 Lambda(t) have been proposed in the literature; we use two different ansatze of varying Lambda and compare the obtained result. We have found that the second ansatz for the varying Lambda, 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 Lambda(H). The cosmographic parameters have been investigated.