Deceleration parameter

About: Deceleration parameter is a research topic. Over the lifetime, 1776 publications have been published within this topic receiving 89440 citations.

Cosmography with the Sunyaev-Zeldovich effect and X-ray data

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 H0−q0 plane is also investigated.

A Dark Energy Quintessence Model of the Universe

Abstract: In this paper, we have presented a model of the FLRW universe filled with matter and dark energy fluids, by assuming an ansatz that deceleration parameter is a linear function of the Hubble constant. This results in a time-dependent DP having decelerating-accelerating transition phase of the universe. This is a quintessence model $\omega_{(de)}\geq -1$. The quintessence phase remains for the period $(0 \leq z \leq 0.5806)$. The model is shown to satisfy current observational constraints. Various cosmological parameters relating to the history of the universe have been investigated.

Power-law entropy-corrected new agegraphic dark energy in Hořava–Lifshitz cosmology

Abstract: We investigate the new agegraphic dark energy (NADE) model with power-law corrected entropy in the framework of Hoyrava-Lifshitz cosmology. For a non-flat universe containing the interacting power-law entropy-corrected NADE (PLECNADE) with dark matter, we obtain the differential equation of the evolution of density parameter as well as the deceleration parameter. To study parametric behavior, we use an interesting form of state parameter as function of redshift !�(z) = !0 + !1z. We find that phantom crossing occurs for the state parameter for a non-zero coupling parameter, thus supporting interacting dark energy model.

Aspects of some new versions of pilgrim dark energy in DGP braneworld

Abstract: The illustration of cosmic acceleration under two interacting dark energy models (pilgrim dark energy with Granda-Oliveros cutoff and its generalized ghost version) in the DGP braneworld framework is presented. In the current scenario, the equation of state parameter, deceleration parameter, $ \omega_{D}$ - $ \omega^{\prime}_{D}$ plane and statefinder diagnosis are investigated. The equation of state parameter behaves like the phantom era of the universe. The deceleration parameter shows the accelerated expansion of the universe in both models. The cosmological planes, like $ \omega_{D}$ - $ \omega^{\prime}_{D}$ , and the statefinder correspond to the $ \Lambda$ CDM limit. To conclude, we remark that our results support the phenomena of pilgrim dark energy and cosmic acceleration. Also, the results are consistent with observational data.

Anisotropic bulk viscous string cosmological models of the Universe under a time-dependent deceleration parameter

Abstract: We investigate a new class of LRS Bianchi type-II cosmological models by revisiting the paper of Mishra et al (Int. J. Theor. Phys. 52, 2546 (2013)) by considering a new deceleration parameter (DP) depending on the time in string cosmology for the modified gravity theory suggested by Saez–Ballester (Phys. Lett. 113, 467 (1986)). We have considered the energy–momentum tensor proposed by Letelier (Phys. Rev. 28, 2414 (1983)) for bulk viscous and perfect fluid under some assumptions. To make our models consistent with recent astronomical observations, we have used the scale factor (Sharma et al, Astron Astrophys. 19, 55 (2018), Garg et al, Int. J. Geo. Meth. Mod. Phys. 16, 1950007 (2019)) $$a(t)=\exp {[\frac{1}{\beta }\sqrt{2 \beta t + k}]}$$ , where $$\beta $$ and k are positive constants and it provides a time-varying DP. By using the recent constraints ( $$H_{0}=73.8$$ and $$q_{0} = -0.54$$ ) from SN Ia data in combination with BAO and CMB observations (Giostri et al, JCAP 3, 27 (2012), arXiv:1203.3213v2[astro-ph.CO]), we affirm $$\beta = 0.0062$$ and $$k = 0.000016$$ . For these constraints, we have substantiated a new class of cosmological transit models for which the expansion takes place from the early decelerated phase to the current accelerated phase. Also, we have studied some physical, kinematic and geometric behaviour of the models, and have found them consistent with observations and well-established theoretical results. We have also compared our present results with those of Mishra et al (Int. J. Theor. Phys. 52, 2546 (2013)) and observed that the results in this paper are much better, stable under perturbation and in good agreement with cosmological reflections.