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 entropy-corrected version of the new agegraphic dark energy (NADE) model and dark matter in a spatially non-flat Universe and in the framework of Hořava-Lifshitz cosmology were studied.
Abstract: We study the entropy-corrected version of the new agegraphic dark energy (NADE) model and dark matter in a spatially non-flat Universe and in the framework of Hořava-Lifshitz cosmology. For the two cases containing noninteracting and interacting entropy-corrected NADE (ECNADE) models, we derive the exact differential equation that determines the evolution of the ECNADE density parameter. Also the deceleration parameter is obtained. Furthermore, using a parametrization of the equation of state parameter of the ECNADE model as ω
Λ(z)=ω
0+ω
1
z, we obtain both ω
0 and ω
1. We find that in the presence of interaction, the equation of state parameter ω
0 of this model can cross the phantom divide line which is compatible with the observation.
8 citations
TL;DR: In this article, the authors investigated the interacting holographic dark energy (HDE) with Granda-Oliveros (GO) IR-cutoff in the framework of Brans-Dicke (BD) cosmology.
Abstract: We investigate the interacting holographic dark energy (HDE) with Granda-Oliveros (GO) IR-cutoff in the framework of Brans-Dicke (BD) cosmology. We obtain the equation of state (EoS) parameter of HDE, $w_D$, the effective EoS parameter $w_{\mathrm{eff}}$, the deceleration parameter $q $ and the squared of sound speed $v_s^2$ in a flat FRW universe. We show that at late time the cosmic coincidence problem can be alleviated. Also we show that for non-interacting case, HDE can give a unified dark matter-dark energy profile in BD cosmology, except that it cannot solve the coincidence problem in the future. By studying the equation of state parameter, we see that the phantom divide may be crossed. Using the latest observational data, we calculate the best values of the parameters for interacting HDE in BD framework. Computing the deceleration parameter implies that the transition from deceleration to the acceleration phase occurred for redshift $z\geq 0.5$. Finally, we investigate the sound stability of the model, and find that HDE with GO cutoff in the framework of BD cosmology can lead to a stable DE-dominated universe favored by observations, provided we take $\beta=0.44$ and $b^2<0.35$. This is in contrast to HDE model in Einstein gravity which does not lead to a stable DE dominated universe.
8 citations
TL;DR: In this article, it was shown that cosmological models with a constant deceleration parameter in general relativity without assuming a specific equation of state are equivalent to those with bulk viscosity.
Abstract: Recently Berman and Gomide have presented cosmological models with a constant deceleration parameter in general relativity without assuming a specific equation of state. It is shown that these models are equivalent to those with bulk viscosity. Some general remarks are made on the former models, including implications for violations of causality.
8 citations
TL;DR: In this paper, the authors examined the prospects for constraining cosmographic parameters from current and future measurements of galaxy clusters distances based on their Sunyaev-Zeldovich effect (SZE) and X-ray observations.
Abstract: Cosmography provides a direct method to map the expansion history of the Universe in a model-independent way. Recently, different kinds of observations have been used in cosmographic analyses, such as SNe Ia and gamma ray bursts measurements, weak and strong lensing, cosmic microwave background anisotropies, etc. In this work we examine the prospects for constraining cosmographic parameters from current and future measurements of galaxy clusters distances based on their Sunyaev-Zeldovich effect (SZE) and X-ray observations. By assuming the current observational error distribution, we perform Monte Carlo simulations based on a well-behaved parameterization for the deceleration parameter to generate samples with different characteristics and study the improvement on the determination of the cosmographic parameters from upcoming data. The influence of galaxy clusters (GC) morphologies on the $H_0- q_0$ plane is also investigated.
8 citations
TL;DR: In this paper, the authors investigated the modified Chaplygin gas (MCG) with interaction between holographic dark energy proposed by Li and dark matter, and the results given by them show such a model can accommodate a transition of the dark energy from a normal state wX > − 1 to wX < − 1 phantom regimes.
Abstract: We investigate the modified Chaplygin gas (MCG) with interaction between holographic dark energy proposed by Li and dark matter. In this model, evolution of the universe is described in detail, which is from deceleration to acceleration. Specifically, the evolutions of related cosmological quantities such as density parameter, the equation of state of holographic dark energy, deceleration parameter and transition redshift are discussed. Moreover, we also give their present values which are consistent with the lately observations. Furthermore, the results given by us show such a model can accommodate a transition of the dark energy from a normal state wX > – 1 to wX < – 1 phantom regimes.
8 citations