Phenomenological dark energy model with hybrid dynamic cosmological constant

Abstract

We investigate Dark Energy by associating it with vacuum energy or Cosmological constant Λ which is taken to be dynamic in nature. Our approach is phenomenological and falls within the domain of variable-Λ Cosmology. However, motivated by quantum theory of metastable vacuum decay, we proposed a new phenomenological decay law of Λ(t) where Λ(t) is a superposition of constant and variable components viz. Λ(t) = ΛC + Λv which is indicated by the word “hybrid dynamic” in the title. By taking a simplified two-fluid scenario with the Universe consisting of Dark Energy and another major component, we found the solutions for three particular phenomenological expressions and made a parametrization of the model in terms of dilution parameter (u). For pressureless Dust and dynamic Dark Energy Universe, we found the matter density and dilution parameter (the dilution parameter has been defined in the text as the exponent of scale factor in the expression of density of the other major component, representing the dilution of the component with the expansion of Universe in the presence of dynamic Dark Energy) to be Ωm0 = 0.29 ± 0.03, u = 2.90 ± 0.54 at 1σ by analysing 580 supernova from Union 2.1 catalogue. The physical features of the model in regard to scale factor evolution, deceleration parameter, cosmic age has also been studied and parallels have been drawn with ΛCDM model. The status of Cosmological problems in the model has also been checked which showed that the model solves the Cosmological Constant Problem but the Coincidence problem still exists in the model.

Further understanding the interaction between dark energy and dark matter: current status and future directions

“…In other works the interaction is not introduced through a kernel but it is described as a modification of the time evolution of cosmological parameters such as the DM density [9,204,252,348] or the cosmic deceleration [245,283] with respect to the standard non-interacting ΛCDM model. Another approach is to parameterize the modifications of the DM perturbations equations in a model-independent way so different models can be described with the same formalism and discriminate modifications of gravity from other effects [30].…”

Interacting Dark Energy: New parametrization and observational constraints

“…the concept of dilution parameter has been introduced in[69] for Λ(t)CDM Cosmology. We have adopted the definition in the context of IDE model…”