Can Dark Energy Emerge from a Varying $G$ and Spacetime Geometry?
Ekim Taylan Hanımeli,
Isaac Tutusaus,
Brahim Lamine
et al.
Abstract:The accelerated expansion of the Universe implies the existence of an energy contribution known as dark energy. Associated with the cosmological constant in the standard model of cosmology, the nature of this dark energy is still unknown. We will discuss an alternative gravity model in which this dark energy contribution emerges naturally, as a result of allowing for a time-dependence on the gravitational constant, G, in Einstein's Field Equations. With this modification, Bianchi's identities require an additi… Show more
“…Refs. [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28] in the recent literature. This is a rather controversial topic [29,30,31].…”
The CPC (Covariant Physical Couplings) framework is a modified gravity set up assuming Einstein Field Equations wherein the quantities {G, c, Λ} are promoted to spacetime 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 parameterization of Λ in terms of the scale factor a. We use the ansatz Ġ/G = σ ( ċ/c) 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.
“…Refs. [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28] in the recent literature. This is a rather controversial topic [29,30,31].…”
The CPC (Covariant Physical Couplings) framework is a modified gravity set up assuming Einstein Field Equations wherein the quantities {G, c, Λ} are promoted to spacetime 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 parameterization of Λ in terms of the scale factor a. We use the ansatz Ġ/G = σ ( ċ/c) 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.
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