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 Bianchi type-V cosmological model with viscous fluid and creation particle in Brans-Dicke theory has been considered and the exact solutions to the corresponding field equations are obtained in quadrature form.
Abstract: The Bianchi type-V cosmological model with viscous fluid and creation particle in Brans-Dicke theory has been considered. The present paper deals with Bianchi type-V cosmological model with bulk viscosity and particle creation described by full causal thermodynamics in Brans-Dicke theory. We have discussed two types of solutions of the average scale factor for a Bianchi type-V model by using a variation law of Hubble’s parameter, which yields a constant value of the deceleration parameter. The exact solutions to the corresponding field equations are obtained in quadrature form. The solutions to the Einstein field equations are obtained for power law and exponential form. The cosmological parameters have been discussed in detail.
8 citations
TL;DR: In this article, the Friedmann Robertson Walker (FRW) model was used to estimate the age of the universe and to find the best fit curves for luminosity distance and apparent magnitude.
Abstract: In the present paper, we have investigated the Friedmann Robertson Walker (FRW) model in viable $f(R,T)$ gravity with $f(R,T)$ function proposed as $f(R,T)=R +\xi T^{1/2}$, where $\xi$ is an arbitrary constant, $R$ is the scalar curvature and $T$ is the trace of stress energy tensor. Defining the scale factor, the field equations are solved numerically and the energy conditions are analyzed. Further, determining Hubble parameter and deceleration parameter, their present values are estimated. Furthermore, 57 redshift data (42 redshift data from Supernova Cosmology project and 15 redshift data from Calan/ Tolono Supernova survey) are used to estimate the age of the universe and to find the best fit curves for luminosity distance and apparent magnitude.
8 citations
TL;DR: In this article, the authors explore possibilities of avoiding coincidence problem in $f(R)$ gravity with a minimally coupled scalar field, and investigate possible behavior of $fR$ to avoid coincidence problem.
Abstract: To explore possibilities of avoiding coincidence problem in $f(R)$ gravity we consider models in Einstein conformal frame which are equivalent to Einstein gravity with a minimally coupled scalar field. As the conformal factor determines the coupling term and hence the interaction between matter and dark energy, the function $f(R)$ can in principle be determined by choosing an appropriate function for the deceleration parameter only. Possible behavior of $f(R)$ to avoid coincidence problem are investigated in two such cases.
8 citations
TL;DR: In this article, the authors considered chameleonic generalized Brans-Dicke cosmology in the framework of Kantwoski-Sacks universes and investigated the time dependence of the Brans Dicke parameter ω(t) for an expanding universe.
Abstract: In this paper we consider chameleonic generalized Brans-Dicke cosmology in the framework of Kantwoski-Sacks universes. We investigate the time dependence of the Brans-Dicke parameter ω(t) for an expanding Universe, and obtain an explicit dependence of ω(t) in different expansion phases of the Universe. Here we take the power law form of the scale factor. The behaviour of ω(t) is studied for matter-dominated, vacuum-energy-dominated universe, radiation-dominated and mass-less scalar-field-dominated era. It is also proposed to study the nature of the deceleration parameter.
8 citations
TL;DR: In this article, a cosmological-model independent framework for the transition redshift was proposed, which determines the onset of cosmic acceleration, in a flat universe and is based on a parametrization for the comoving distance.
Abstract: This paper aims to put constraints on the transition redshift $z_t$, which determines the onset of cosmic acceleration, in cosmological-model independent frameworks. In order to perform our analyses, we consider a flat universe and {assume} a parametrization for the comoving distance $D_C(z)$ up to third degree on $z$, a second degree parametrization for the Hubble parameter $H(z)$ and a linear parametrization for the deceleration parameter $q(z)$. For each case, we show that {type Ia supernovae} and $H(z)$ data complement each other on the parameter {space} and tighter constrains for the transition redshift are obtained. By {combining} the type Ia supernovae observations and Hubble parameter measurements it is possible to constrain the values of $z_t$, for each approach, as $0.806\pm 0.094$, $0.870\pm 0.063$ and $0.973\pm 0.058$ at 1$\sigma$ c.l., respectively. Then, such approaches provide cosmological-model independent estimates for this parameter.
8 citations