Asymptotically Static Universe Dominated by Phantom Energy

Abstract

In this article, we investigated a generalised scalar field cosmology characterised by a time-dependent coupling function, a time-dependent cosmological constant, a chameleonic field, and a time-dependent equation of state parameter. Based on a particular choice of the Hubble parameter as function of the scalar field and its time derivative, we have investigated the dynamics of the Friedmann-Robertson-Walker flat universe. We have observed that for a particular choice of the free parameters in the theory, the universe accelerates with time and asymptotically tends toward a static universe. For specific values of the free parameters, the asymptotically static universe may be dominated by phantom energy or a cosmological constant without the need to implement in the theory multiple scalar fields or additional interactions. It is also pointed out that an asymptotically static universe is as well one special class of solutions for Horndeski and generalised galileons cosmologies. Special properties and features are discussed accordingly.

Viscous string cosmological models in alternative theory of gravity

“…45 Recent past several researchers including our research group 38 have been studied many cosmological models of the universe with time varying q , in different context. [46][47][48][49][50][51][52][53] Now, the general solution of equation ( 36) is derived by our research team, 38 where we have defined 2 = ( )= / q b t aa a −   . The motivation to choose this type of DP is behind the fact that universe has an accelerating expanding phase at present time as observed by SNeIa supernova observations 4,8 and decelerated expansion in the past but in present scenario DP must show signature flipping, 5,54,55 so in general DP is not a constant but time variable so that above equation ( 36) may be re written as = ( ( ))…”

A General Bianchi Type Viscous Fluid Cosmological Model with Both Deceleration and Acceleration

“…From equation [17] we observe that final stage of the universe is neither accelerating or decelerating but approaches an asymptotically static homogeneous universe for specific values of the parameter which could play a vital role in the future evolution of the universe [34,35].…”

Non-Minimally Conformally Coupling Cosmology with Multiple Vacua Potential with Cubic-Quintic-Septic Duffing Oscillator Properties

“…From this analysis, we will conjecture that the scalar factor and the scalar field are related the law a(t) ∝ φ ε (t), ε being a real dimensionless parameter. Relations between the scalar field and the scale factor were considered in fact in many cosmological scenarios [33][34][35][36][37][38][39][40][41][42]. Besides, we assume that the universe is filled by a perfect fluid of density ρ and pressure p with the equation of state p = (γ − 1) ρ where γ is assumed to be a time-dependent parameter.…”

“…As the scalar field evolves with time, one can therefore express the Hubble parameter or the scale factor (depending on the ansatz considered) as a function of the scalar field instead of as a function of time [46]. This method is used in different cosmological scenarios [33][34][35][36][37][38][39][40][41][42] and in constructing exact inflationary solution in non-minimally chaotic inflation model [47] as well as many exact inflationary models [48,49]. This method is commendable, as all field equations are expressed in terms of the scalar field, and therefore, depending on the model under study, there is no need to neglect frictions terms in the field equations for example or assume that that they are dominant with respect to the kinetic energy of the scalar field.…”