Topic
Deceleration parameter
About: Deceleration parameter is a research topic. Over the lifetime, 1776 publications have been published within this topic receiving 89440 citations.
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TL;DR: In this paper, the existence of the late time acceleration of the universe filled with cosmic fluid and uniform magnetic field as source of matter in anisotropic Heckmann-Schucking space-time has been explained by introducing a positive cosmological constant in the Einstein's field equation.
Abstract: In the present work we have searched the existence of the late time acceleration of the Universe filled with cosmic fluid and uniform magnetic field as source of matter in anisotropic Heckmann-Schucking space-time. The observed acceleration of universe has been explained by introducing a positive cosmological constant $\varLambda$
in the Einstein’s field equation which is mathematically equivalent to vacuum energy with equation of state (EOS) parameter set equal to −1. The present values of the matter and the dark energy parameters $(\varOmega_{m})_{0}$
& $(\varOmega_{\varLambda})_{0}$
are estimated in view of the latest 287 high red shift (
$0.3 \leq z \leq1.4$
) SN Ia supernova data’s of observed apparent magnitude along with their possible error taken from Union 2.1 compilation. It is found that the best fit value for $(\varOmega_{m})_{0}$
& $(\varOmega_{\varLambda})_{0}$
are 0.2820 & 0.7177 respectively which are in good agreement with recent astrophysical observations in the latest surveys like WMAP [2001–2013], Planck [latest 2015] & BOSS. Various physical parameters such as the matter and dark energy densities, the present age of the universe and deceleration parameter have been obtained on the basis of the values of $(\varOmega_{m})_{0}$
& $(\varOmega_{\varLambda})_{0}$
. Also we have estimated that the acceleration would have begun in the past at $z = 0.71131 \thicksim6.2334~\mbox{Gyrs}$
before from present.
32 citations
TL;DR: In this article, a generalized parametrization for the deceleration parameter q in order to study the evolutionary history of the universe is proposed, and the proposed model can be used to model the entire universe.
Abstract: In this paper, we have proposed a generalized parametrization for the deceleration parameter q in order to study the evolutionary history of the universe. We have shown that the proposed model can ...
32 citations
TL;DR: In this paper, the authors search for the existence of the late time acceleration of the universe with string fluid as the source of matter in Bianchi-V space-time and derive a deterministic solution, choosing the scale factor to be an increasing function of time that yields a time dependent deceleration parameter.
Abstract: We have searched for the existence of the late time acceleration of the universe with string fluid as the source of matter in Bianchi—V space-time. To derive a deterministic solution, we choose the scale factor to be an increasing function of time that yields a time dependent deceleration parameter, representing a model which generates a universe showing a transition from an early decelerating phase to a recent accelerating phase. The study reveals that strings dominate the early universe and eventually disappear from the universe for sufficiently large times, i.e. in the present epoch. This picture is consistent with current astronomical observations. The physical behavior of the universe is discussed in detail.
32 citations
TL;DR: In this article, a form for the Hubble parameter was used to generate a number of solutions to the Einstein field equations with variable cosmological constant and variable gravitational constant in the presence of a bulk viscous fluid.
Abstract: We utilise a form for the Hubble parameter to generate a number of solutions to the Einstein field equations with variable cosmological constant and variable gravitational constant in the presence of a bulk viscous fluid. The Hubble law utilised yields a constant value for the deceleration parameter. A new class of solutions is presented in the Robertson–Walker spacetimes. The coefficient of bulk viscosity is assumed to be a power function of the mass density. For a class of solutions, the deceleration parameter is negative which is consistent with the supernovae Ia observations.
32 citations
TL;DR: In this paper, the authors considered a modified holographic Ricci DE (which is function of the Hubble parameter and its first derivative with respect to cosmic time, t) in light of the f(R, T) model of modified gravity, and they observed that the fractional energy densities for DE and dark matter have an increasing and a decreasing pattern, respectively, with the evolution of the universe, indicating an evolution from matter to DE dominated universe.
Abstract: In this paper, we consider a recently proposed model of dark energy (DE) know as modified holographic Ricci DE (which is function of the Hubble parameter and its first derivative with respect to cosmic time, t) in light of the f(R, T) model of modified gravity, considering the particular model f(R, T) = μR + νT, with μ and ν constants. The equation of state parameter ωΛ approaches but never reaches the value −1, implying a quintessence-like behavior of the model. The deceleration parameter q passes from decelerated to accelerated phase at a redshift of z ≈ 0.2, showing also a small dependence from the values of the parameters considered. Thanks to the statefinder diagnostic analysis, we observed that the ΛCDM phase for the considered model is attainable. We observed that the fractional energy densities for DE and dark matter, ΩΛ and Ωm, have an increasing and a decreasing pattern, respectively, with the evolution of the universe, indicating an evolution from matter to DE dominated universe. Finally, study...
32 citations