Testing a varying-Λ model for dark energy within co-varying physical couplings framework

Abstract

ABSTRACT The Co-varying Physical Couplings (CPC) framework is a modified gravity set up assuming Einstein Field Equations wherein the quantities {G, c, Λ} are promoted to space–time functions. Bianchi identity and the requirement of stress-energy tensor conservation entangle the possible variations of the couplings {G, c, Λ}, which are forced to co-vary as dictated by the General Constraint (GC). In this paper, we explore a cosmological model wherein G, c, and Λ are functions of the redshift respecting the GC of the CPC framework. We assume a linear parametrization of Λ in terms of the scale factor a. We use the ansatz $\dot{G}/G = \sigma \left(\dot{c}/c \right)$ with σ = constant to deduce the functional forms of c = c(z) and G = G(z). We show that this varying-{G, c, Λ} model fits SNe Ia data and H(z) data with σ = 3. The model parameters can be constrained to describe dark energy at the background level.