scholarly journals Generalized ghost dark energy in Brans–Dicke theory

2013 ◽  
Vol 91 (8) ◽  
pp. 662-667 ◽  
Author(s):  
A. Sheykhi ◽  
E. Ebrahimi ◽  
Y. Yousefi
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Dark Energy Model ◽  
Vacuum Energy ◽  
State Parameter ◽  
Energy Model ◽  
Time Dependent ◽  
Ghost Dark Energy ◽  
Ghost Field ◽  
Generalized Ghost Dark Energy

It was argued that the vacuum energy of the Veneziano ghost field of QCD, in a time-dependent background, can be written in the general form, H + O(H2), where H is the Hubble parameter. Based on this, a phenomenological dark energy model whose energy density is of the form ρ = αH + βH2 was recently proposed to explain the dark energy dominated universe. In this paper, we investigate this generalized ghost dark energy model in the setup of Brans–Dicke cosmology. We study the cosmological implications of this model. In particular, we obtain the equation of state, the deceleration parameters, and a differential equation governing the evolution of this dark energy model. It is shown that the equation of state parameter of the generalized ghost dark energy can cross the phantom line (wD = −1) in some range of the parameters spaces.

Cosmic evolution of ghost dark energy models in f(G,T) gravity

2019 ◽  
Vol 35 (10) ◽  
pp. 2050063
Author(s):  
M. Sharif ◽  
Saadia Saba
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Speed Of Sound ◽  
Dark Energy Model ◽  
State Parameter ◽  
Energy Model ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Generalized Ghost Dark Energy

The aim of this paper is to study the reconstruction paradigm for both ghost as well as generalized ghost dark energy models in the context of [Formula: see text] gravity. To accomplish this, we use correspondence scenario for pressureless flat FRW universe with power-law scale factor. The cosmological behavior of reconstructed models is analyzed through graphical analysis of deceleration, equation of state, squared speed of sound parameters and phase planes. It is found that the deceleration parameter represents accelerated epoch for both models whereas equation of state parameter indicates phantom era of the universe for ghost dark energy model and quintessence for its generalized version. The phase planes [Formula: see text] and [Formula: see text] indicate the freezing region with phantom phase for both reconstructed dark energy models. We conclude that the squared speed of sound parameter leads to the stability of generalized ghost dark energy model only.

Chaplygin scalar field reconstruction of the modified ghost dark energy model

2015 ◽  
Vol 93 (8) ◽  
pp. 855-861
Author(s):  
Kayoomars Karami
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Equation Of State ◽  
Energy Density ◽  
Dark Energy Model ◽  
State Parameter ◽  
Energy Model ◽  
Density Parameter ◽  
Dark Energy Density ◽  
Ghost Dark Energy

Within the framework of Einstein gravity, we establish a correspondence between the Chaplygin scalar field model and the modified ghost dark energy model. We consider a spatially non-flat Friedmann–Robertson–Walker universe containing modified ghost dark energy and dark matter that are in interaction with each other. We solve the differential equation governing the dimensionless modified ghost dark energy density parameter numerically. Then we obtain the evolutionary behaviors of both the energy density and equation of state parameters of the modified ghost dark energy. More interesting is that the equation of state parameter at the present time can cross the phantom divide line provided the interaction parameter b2 > 0.15 is compatible with the observations. Furthermore, we reconstruct both the Chaplygin gas scalar field and potential according to the evolutionary behavior of the modified ghost dark energy model.

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 Interacting generalized ghost dark energy in a non-flat universe

Open Physics ◽  
2013 ◽  
Vol 11 (7) ◽  
Author(s):  
Esmaeil Ebrahimi ◽  
Ahmad Sheykhi ◽  
Hamzeh Alavirad
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
State Parameter ◽  
Model Parameters ◽  
De Sitter ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Equation Of State Parameter ◽  
The Universe ◽  
Generalized Ghost Dark Energy

AbstractWe investigate the generalized Quantum Chromodynamics (QCD) ghost model of dark energy in the framework of Einstein gravity. First, we study the non-interacting generalized ghost dark energy in a flat Friedmann-Robertson-Walker (FRW) background. We obtain the equation of state parameter, w D = p/ρ, the deceleration parameter, and the evolution equation of the generalized ghost dark energy. We find that, in this case, w D cannot cross the phantom line (w D > −1) and eventually the universe approaches a de-Sitter phase of expansion (w D → −1). Then, we extend the study to the interacting ghost dark energy in both a flat and non-flat FRW universe. We find that the equation of state parameter of the interacting generalized ghost dark energy can cross the phantom line (w D < −1) provided the parameters of the model are chosen suitably. Finally, we constrain the model parameters by using the Markov Chain Monte Carlo (MCMC) method and a combined dataset of SNIa, CMB, BAO and X-ray gas mass fraction.

scholarly journals MODIFIED HOLOGRAPHIC RICCI DARK ENERGY MODEL AND STATEFINDER DIAGNOSIS IN FLAT UNIVERSE

2013 ◽  
Vol 22 (09) ◽  
pp. 1350056 ◽  
Author(s):  
TITUS K. MATHEW ◽  
JISHNU SURESH ◽  
DIVYA DIVAKARAN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Dark Energy Model ◽  
Cold Dark Matter ◽  
State Parameter ◽  
Energy Model ◽  
Model Parameters ◽  
Ricci Dark Energy ◽  
Evolutionary Trajectories ◽  
Parameter Values

Evolution of the universe with modified holographic Ricci dark energy model is considered. Dependency of the equation of state parameter and deceleration parameter on the redshift and model parameters are obtained. It is shown that the density evolution of both the nonrelativistic matter and dark energy are same until recent times. The evolutionary trajectories of the model for different model parameters are obtained in the statefinder planes, r – s and r – q planes. The present statefinder parameters are obtained for different model parameter values, using that the model is differentiated from other standard models like the ΛCDM model. We have also shown that the evolutionary trajectories are depending on the model parameters, and at past times the dark energy is behaving like cold dark matter, with equation of state equal to zero.

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