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 article, the authors obtained tight estimates on the Hubble constant by considering two data sets from galaxy distribution observations: galaxy cluster gas mass fractions and baryon acoustic oscillation measurements.
Abstract: An accurate determination of the Hubble constant remains a puzzle in observational cosmology. The possibility of a new physics has emerged with a significant tension between the current expansion rate of our Universe measured from the cosmic microwave background by the Planck satellite and from local methods. In this paper, new tight estimates on this parameter are obtained by considering two data sets from galaxy distribution observations: galaxy cluster gas mass fractions and baryon acoustic oscillation measurements. Priors from the Big Bang nucleosynthesis (BBN) were also considered. By considering the flat $\Lambda$CDM and XCDM models, and the non-flat $\Lambda$CDM model, our main results are: $H_0=65.9^{+1.5}_{-1.5}$ km s$^{-1}$ Mpc$^{-1}$, $H_0=65.9^{+4.4}_{-4.0}$ km s$^{-1}$ Mpc$^{-1}$ and $H_0=64.3^{+ 4.5}_{- 4.4}$ km s$^{-1}$ Mpc$^{-1}$ in $2\sigma$ c.l., respectively. These estimates are in full agreement with the Planck satellite results. Our analyses in these cosmological scenarios also support a negative value for the deceleration parameter at least in 3$\sigma$ c.l..
8 citations
TL;DR: In this paper, the authors considered a generalized version of the holographic dark energy (GHDE) model, in which the model parameter ccffff 2 evolves slowly with time, and the evolution of energy density of the model was investigated in terms of this parameter.
Abstract: We consider the holographic dark energy model in which the model parameter c
2 evolves slowly with time. First we calculate the evolution of EoS parameter as well as the deceleration parameter in this generalized version of holographic dark energy (GHDE). Depending on the parameter c
2, the phantom regime can be achieved earlier or later compare with original version of holographic dark energy. The evolution of energy density of GHDE model is investigated in terms of parameter c
2. We also show that the time-dependency of c
2 can effect on the transition epoch from decelerated phase to accelerated expansion. Finally, we perform the statefinder diagnostic for GHDE model and show that the evolutionary trajectories of the model in s–r plane are strongly depend on the parameter c
2.
8 citations
TL;DR: In this article, the authors investigate the validity of generalized second law of thermodynamics by using first law and Bekenstein, logarithmic and power-law horizon entropies.
8 citations
TL;DR: In this article, a reconstruction scheme for f(T) gravity considering the scale factor in the power law form was reported, and the equation of state parameter has been studied for this reconstructed model along with the deceleration parameter and the statefinder pair.
Abstract: The present study reports a reconstruction scheme for f(T) gravity considering the scale factor in the power law form. The equation of state parameter has been studied for this reconstructed model along with the deceleration parameter and the statefinder pair {r,s}. The statefinder trajectory has been found to interpolate between dust and ΛCDM phase of the universe. Cosmological evolution of primordial perturbations has been studied through scalar metric fluctuations and finally the reconstructed f(T) model has been tested for its consistency with the generic expansion of the universe.
8 citations
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TL;DR: In this article, a spatially homogeneous and anisotropic Bianchi type V space-time with bulk viscous fluid source and time varying gravitational constant $G$ and cosmological term $\Lambda$ are considered.
Abstract: Spatially homogeneous and anisotropic Bianchi type V space-time with bulk viscous fluid source and time varying gravitational constant $G$ and cosmological term $\Lambda$ are considered. Coefficient of bulk viscosity $\zeta$ is assumed as a simple linear function of Hubble parameter $H$ (i.e. $\zeta=\zeta_0+\zeta_1 H$, where $\zeta_0$ and $\zeta_1$ are constants). The Einstein field equations are solved explicitly by using a law of variation for the Hubble parameter, which yields a constant value of deceleration parameter. Physical and kinematical parameters of the models are discussed. The models are found to be compatible with the results of astronomical observations.
8 citations