scholarly journals Analysis off(R)Theory Corresponding to NADE and NHDE

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
M. Sharif ◽  
M. Zubair
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Future Evolution ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Effective Description

We develop the connection off(R)theory with new agegraphic and holographic dark energy models. The functionf(R)is reconstructed regarding thef(R)theory as an effective description for these dark energy models. We show the future evolution offand conclude that these functions represent distinct pictures of cosmological eras. The cosmological parameters such as equation of state parameter, deceleration parameter, statefinder diagnostic, andw−w′analysis are investigated which assure the evolutionary paradigm off.

scholarly journals Reconstruction of interaction rate in holographic dark energy model with Hubble horizon as the infrared cut-off

2017 ◽  
Vol 26 (11) ◽  
pp. 1750136 ◽  
Author(s):  
Abdulla Al Mamon
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Energy Equation ◽  
Present Model ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Model Parameters ◽  
Interaction Rate ◽  
Equation Of State Parameter

This work is the reconstruction of the interaction rate of holographic dark energy whose infrared cut-off scale is set by the Hubble length. We have reconstructed the interaction rate between dark matter and the holographic dark energy for a specific parameterization of the effective equation-of-state parameter. We have obtained observational constraints on the model parameters using the latest type Ia supernova (SNIa), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB) radiation datasets. We have found that for the present model, the interaction rate increases with expansion and remains positive throughout the evolution. For a comprehensive analysis, we have also compared the reconstructed results of the interaction rate with other well-known holographic dark energy models. The nature of the deceleration parameter, the statefinder parameters and the dark energy equation-of-state parameter have also been studied for the present model. It has been found that the deceleration parameter favors the past decelerated and recent accelerated expansion phase of the universe. It has also been found that the dark energy equation-of-state parameter shows a phantom nature at the present epoch.

scholarly journals Cosmological aspects of sound speed parameterizations in fractal universe

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Abdul Jawad ◽  
Sadaf Butt ◽  
Shamaila Rani ◽  
Khadija Asif
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Graphical Analysis ◽  
Eos Parameter ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
The Universe

AbstractIn the framework of fractal universe, the unified models of dark energy and dark matter are being presented with the background of homogenous and isotropic FLRW geometry. The aspects of fractal cosmology helps in better understanding of the universe in different dimensions. Relationship between the squared speed of the sound and the equation of state parameter is the key feature of these models. We have used constant as well as variable forms of speed of sound and express it as a function of equation of state parameter. By utilizing the four different forms of speed of sound, we construct the energy densities and pressures for these models and then various cosmological parameters like hubble parameter, EoS parameter, deceleration parameter and Om- diagnostic are investigated. Graphical analysis of these parameters show that in most of the cases EoS parameters and trajectories of Om-diagnostic corresponds to the quintessence like nature of the universe and the deceleration parameters represent accelerated and decelerated phase. In the end, we remark that cosmological analysis of these models indicates that these models correspond to different well known dark energy models.

scholarly journals DARK ENERGY MODELS WITH VARIABLE EQUATION OF STATE PARAMETER

2010 ◽  
Vol 19 (04) ◽  
pp. 475-487 ◽  
Author(s):  
UTPAL MUKHOPADHYAY ◽  
SAIBAL RAY ◽  
FAROOK RAHAMAN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
State Parameter ◽  
Five Dimensions ◽  
Energy Models ◽  
Variable Λ ◽  
Equation Of State Parameter ◽  
Variable Equation

Two phenomenological variable Λ models, viz.Λ ~ (ȧ/a)2 and Λ ~ ρ, have been studied under the assumption that the equation of state parameter ω is a function of time. The selected Λ models are found to be equivalent both in four and five dimensions. The possibility of signature flip of the deceleration parameter is also shown.

Generalized ghost Tsallis holographic dark energy model in RS-II braneworld and dynamical Chern-Simons modified gravity

2020 ◽  
Vol 17 (08) ◽  
pp. 2050124
Author(s):  
Abdul Jawad ◽  
Sabir Hussain ◽  
Shamaila Rani ◽  
Saba Qummer
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Modified Gravity ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Frw Universe ◽  
Om Diagnostic ◽  
Equation Of State Parameter ◽  
Chern Simons

In this paper, we studied the cosmological implications of generalized ghost Tsallis holographic dark energy in the framework of Randall–Sundrum II braneworld and Chern–Simons modified gravity in flat FRW universe. We discuss the cosmological parameters like equation of state parameter, deceleration parameter, squared speed of sound, Om-diagnostic and planes like evolving equation of state parameter and statefinders. These models yield useful results in this context.

Cosmological evolution of non-interacting and interacting holographic dark energy model in Brans–Dicke theory

2018 ◽  
Vol 15 (07) ◽  
pp. 1850124 ◽  
Author(s):  
Milan Srivastava ◽  
C. P. Singh
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Deceleration Parameter ◽  
Holographic Dark Energy ◽  
Coupling Parameter ◽  
State Parameter ◽  
Late Time ◽  
Coincidence Problem ◽  
Logarithmic Form ◽  
Equation Of State Parameter

The purpose of this paper is to study the dynamics of non-interacting and interacting holographic dark energy (HDE) models in the framework of Brans–Dicke (BD) cosmology. As system’s infrared cutoff, we consider the future event horizon. The scalar function of BD theory is assumed to be a logarithmic form of scale factor, which is claimed to avoid a constant result for deceleration parameter. We investigate the cosmological implications of this model in detail. We obtain the time-dependent equation of state parameter and deceleration parameter which describe the phase transition of the Universe. We observe that the model explains the early time inflation and late time acceleration including matter-dominated phase. It is also observed that the equation of state parameter may cross phantom divide line in late time evolution. The cosmic coincidence problem is also discussed for both the models. We observe that this logarithmic form of Brans–Dicke scalar field is more appropriate to achieve a less acute coincidence problem in non-interacting model whereas a soft coincidence can be achieved if coupling parameter in interacting model has small value.

scholarly journals Cosmological Consequences of New Dark Energy Models in Einstein-Aether Gravity

Symmetry ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 509 ◽  
Author(s):  
Shamaila Rani ◽  
Abdul Jawad ◽  
Kazuharu Bamba ◽  
Irfan Malik
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Graphical Representation ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Effective Density ◽  
Evolutionary Equation ◽  
Model Parameters ◽  
Energy Models ◽  
Equation Of State Parameter

In this paper, we reconstruct various solutions for the accelerated universe in the Einstein-Aether theory of gravity. For this purpose, we obtain the effective density and pressure for Einstein-Aether theory. We reconstruct the Einstein-Aether models by comparing its energy density with various newly proposed holographic dark energy models such as Tsallis, Rényi and Sharma-Mittal. For this reconstruction, we use two forms of the scale factor, power-law and exponential forms. The cosmological analysis of the underlying scenario has been done by exploring different cosmological parameters. This includes equation of state parameter, squared speed of sound and evolutionary equation of state parameter via graphical representation. We obtain some favorable results for some values of model parameters

scholarly journals Cosmological Implications of the Generalized Entropy Based Holographic Dark Energy Models in Dynamical Chern-Simons Modified Gravity

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
M. Younas ◽  
Abdul Jawad ◽  
Saba Qummer ◽  
H. Moradpour ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Modified Gravity ◽  
Dark Energy Model ◽  
State Parameter ◽  
Energy Model ◽  
Evolutionary Equation ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Chern Simons

Recently, Tsallis, Rényi, and Sharma-Mittal entropies have widely been used to study the gravitational and cosmological setups. We consider a flat FRW universe with linear interaction between dark energy and dark matter. We discuss the dark energy models using Tsallis, Rényi, and Sharma-Mittal entropies in the framework of Chern-Simons modified gravity. We explore various cosmological parameters (equation of state parameter, squared sound of speed ) and cosmological plane (ωd-ωd′, where ωd′ is the evolutionary equation of state parameter). It is observed that the equation of state parameter gives quintessence-like nature of the universe in most of the cases. Also, the squared speed of sound shows stability of Tsallis and Rényi dark energy model but unstable behavior for Sharma-Mittal dark energy model. The ωd-ωd′ plane represents the thawing region for all dark energy models.

Viability of specific reconstructed f(T,𝒯 ) models

2019 ◽  
Vol 34 (30) ◽  
pp. 1950184
Author(s):  
M. Umair Shahzad ◽  
Nadeem Azhar ◽  
Abdul Jawad ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Dark Energy Model ◽  
State Parameter ◽  
Pilgrim Dark Energy ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Equation Of State Parameter ◽  
Hubble Horizon ◽  
The Universe

The reconstruction scenario of well-established dark energy models such as pilgrim dark energy model and generalized ghost dark energy with Hubble horizon and [Formula: see text] models is being considered. We have established [Formula: see text] models and analyzed their viability through equation of state parameter and [Formula: see text] (where prime denotes derivative with respect to [Formula: see text]) plane. The equation of state parameter evolutes the universe in three different phases such as quintessence, vacuum and phantom. However, the [Formula: see text] plane also describes the thawing as well as freezing region of the universe. The recent observational data also favor our results.

scholarly journals THE EFFECT OF DIFFERENT OBSERVATIONAL DATA IN CONSTRAINING COSMOLOGICAL PARAMETERS

2012 ◽  
Vol 10 ◽  
pp. 85-94 ◽  
Author(s):  
YUNGUI GONG ◽  
QING GAO ◽  
ZONG-HONG ZHU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Observational Data ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Model Parameters ◽  
Type Ia Supernova ◽  
Equation Of State Parameter ◽  
Type Ia

We use the SNLS3 compilation of 472 type Ia supernova data, the baryon acoustic oscillation measurement of distance, and the cosmic microwave background radiation data from the seven year Wilkinson Microwave Anisotropy Probe to study the effect of their different combinations on the fittings of cosmological parameters. Neither BAO nor WMAP7 data alone gives good constraint on the equation of state parameter of dark energy, but both WMAP7 data and BAO data help type Ia supernova data break the degeneracies among the model parameters, hence tighten the constraint on the variation of equation of state parameter wa, and WMAP7 data does the job a little better. Although BAO and WMAP7 data provide reasonably good constraints on Ωm and Ωk, it is not able to constrain the dynamics of dark energy, we need SNe Ia data to probe the property of dark energy, especially the variation of the equation of state parameter of dark energy. For the SNLS SNe Ia data, the nuisance parameters α and β are consistent for all different combinations of the above data. Their impacts on the fittings of cosmological parameters are minimal. ΛCDM model is consistent with current observational data.

Accreting Scalar-Field Models of Dark Energy Onto Morris-Thorne Wormhole

2016 ◽  
Vol 71 (10) ◽  
pp. 949-960
Author(s):  
Surajit Chattopadhyay ◽  
Antonio Pasqua ◽  
Irina Radinschi
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Power Law ◽  
State Parameter ◽  
Suitable Choice ◽  
Energy Models ◽  
Scalar Field Models ◽  
Equation Of State Parameter ◽  
Phantom Phase

AbstractThe present paper reports a study on accreting tachyon, Dirac-Born-Infeld essence and h-essence scalar field models of dark energy onto Morris-Thorne wormhole. Using three different parameterisation schemes and taking $H\, = \,{H_0}\, + \,{{{H_1}} \over t}$, we have derived the mass of the wormhole for all of the three parameterisation schemes that are able to get hold of both quintessence and phantom behaviour. With suitable choice of parameters, we observed that accreting scalar field dark energy models are increasing the mass of the wormhole in the phantom phase and the mass is decreasing in the quintessence phase. Finally, we have considered accretion with power law form of scale factor and without any parameterisation scheme for the equation of state parameter and observed the fact that phantom-type dark energy supports the existence of wormholes.

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