scholarly journals Tsallis Holographic Dark Energy in f(G,T) Gravity

Symmetry ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 92 ◽  
Author(s):  
Muhammad Sharif ◽  
Saadia Saba
Keyword(s):  
Dark Energy ◽  
Energy Momentum Tensor ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Momentum Tensor ◽  
Chaplygin Gas ◽  
Holographic Dark Energy Model ◽  
Phantom Phase ◽  
Friedmann Robertson Walker ◽  
Fluid Configuration

In this paper, we study the reconstruction paradigm for Tsallis holographic dark energy model using generalized Tsallis entropy conjecture with Hubble horizon in the framework of f ( G , T ) gravity (G and T represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor). We take the flat Friedmann-Robertson-Walker universe model with dust fluid configuration. The cosmological evolution of reconstructed models is examined through cosmic diagnostic parameters and phase planes. The equation of the state parameter indicates phantom phase while the deceleration parameter demonstrates accelerated cosmic epoch for both conserved as well as non-conserved energy-momentum tensor. The squared speed of the sound parameter shows instability of the conserved model while stable non-conserved model for the entire cosmic evolutionary paradigm. The trajectories of the ω G T - ω G T ′ plane correspond to freezing as well as thawing regimes for the conserved and non-conserved scenario, respectively. The r - s plane gives phantom and quintessence dark energy epochs for conserved while Chaplygin gas model regime for the non-conserved case. We conclude that, upon the appropriate choice of the free parameters involved, the derived models demonstrate a self-consistent phantom universe behavior.

scholarly journals Cosmic Evolution of Holographic Dark Energy in f(G,T) Gravity

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Phase Plane ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Momentum Tensor ◽  
Chaplygin Gas ◽  
Cosmic Evolution ◽  
Evolutionary Trajectories ◽  
The Universe

The aim of this paper is to analyze the cosmological evolution of holographic dark energy in f(G,T) gravity (G and T represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor, respectively). We reconstruct f(G,T) model through correspondence scheme using power-law form of the scale factor. The qualitative analysis of the derived model is investigated with the help of evolutionary trajectories of equation of state and deceleration as well as state-finder diagnostic parameters and ωGT-ωGT′ cosmological phase plane. It is found that the equation of state parameter represents phantom epoch of the Universe whereas the deceleration parameter illustrates the accelerated phase. The state-finder plane corresponds to Chaplygin gas model while the freezing region is attained in ωGT-ωGT′ plane.

Generalized ghost pilgrim dark energy in f(G,T) gravity

2019 ◽  
Vol 28 (06) ◽  
pp. 1950077 ◽  
Author(s):  
M. Sharif ◽  
Saadia Saba
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
Momentum Tensor ◽  
Chaplygin Gas ◽  
Frw Universe ◽  
Pilgrim Dark Energy ◽  
Energy Formula ◽  
Text Model ◽  
The Universe ◽  
Friedmann Robertson Walker

In this paper, we explore the reconstruction paradigm for generalized ghost pilgrim dark energy model with [Formula: see text] gravity ([Formula: see text] is the Gauss–Bonnet invariant and [Formula: see text] is the trace of the energy–momentum tensor) depending upon the speculation of black hole-free universe. To accomplish this, we adopt correspondence scheme for dust fluid configuration with flat Friedmann-Robertson-Walker (FRW) universe. The cosmic behavior of reconstructed models is examined through cosmological diagnostic parameters and phase planes. It is found that the deceleration parameter indicates accelerated phase while equation-of-state parameter represents phantom regime for some specific range of free parameters. The squared speed of sound parameter gives stable models for analyzing evolutionary paradigm of the universe. The trajectories of [Formula: see text]–[Formula: see text] plane gives thawing region, whereas [Formula: see text]–[Formula: see text] phase plane corresponds to Chaplygin gas model. We conclude that the resulting model represents self-consistent phantom-like universe for [Formula: see text] cannot be fraction) as well as stable generalized ghost pilgrim dark energy [Formula: see text] model.

Various dark energy models for variables G and Λ in f(R, T) modified theory

2019 ◽  
Vol 34 (13) ◽  
pp. 1950098 ◽  
Author(s):  
Can Aktaş
Keyword(s):  
Dark Energy ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Tachyon Field ◽  
Field Equations ◽  
Frw Universe ◽  
Linearly Varying Deceleration Parameter ◽  
Energy Models ◽  
Modified Theory ◽  
Friedmann Robertson Walker

In this paper, we have researched tachyon field, k-essence and quintessence dark energy (DE) models for Friedmann–Robertson–Walker (FRW) universe with varying G and [Formula: see text] in f(R, T) gravitation theory. The theory of f(R, T) is proposed by Harko et al. [Phys. Rev. D 84, 024020, 2011]. In this theory, R is the Ricci scalar and T is the trace of energy–momentum tensor. For the solutions of field equations, we have used linearly varying deceleration parameter (LVDP), the equation of state (EoS) and the ratio between [Formula: see text] and Hubble parameter. Also, we have discussed some physical behavior of the models with various graphics.

scholarly journals Spinor Quintom Cosmology with Intrinsic Spin

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Emre Dil
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Dark Energy Model ◽  
Energy Momentum Tensor ◽  
State Parameter ◽  
Momentum Tensor ◽  
Big Rip ◽  
Equation Of State Parameter ◽  
Spin Contribution ◽  
Distance Parameter

We consider a spinor quintom dark energy model with intrinsic spin, in the framework of Einstein-Cartan-Sciama-Kibble theory. After constructing the mathematical formalism of the model, we obtain the spin contributed total energy-momentum tensor giving the energy density and the pressure of the quintom model, and then we find the equation of state parameter, Hubble parameter, deceleration parameter, state finder parameter, and some distance parameter in terms of the spinor potential. Choosing suitable potentials leads to the quintom scenario crossing between quintessence and phantom epochs, or vice versa. Analyzing three quintom scenarios provides stable expansion phases avoiding Big Rip singularities and yielding matter dominated era through the stabilization of the spinor pressure via spin contribution. The stabilization in spinor pressure leads to neglecting it as compared to the increasing energy density and constituting a matter dominated stable expansion epoch.

scholarly journals RECONSTRUCTION OF NEW HOLOGRAPHIC SCALAR FIELD MODELS OF DARK ENERGY IN BRANS–DICKE UNIVERSE

2011 ◽  
Vol 26 (03) ◽  
pp. 191-204 ◽  
Author(s):  
WEI-QIANG YANG ◽  
YA-BO WU ◽  
LI-MIN SONG ◽  
YANG-YANG SU ◽  
JIAN LI ◽  
...  
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Chaplygin Gas ◽  
Energy Model ◽  
Accelerated Expansion ◽  
Holographic Dark Energy Model ◽  
Special Cases ◽  
Expansion Of The Universe

Motivated by the work: K. Karami and J. Fehri, Phys. Lett. B684, 61 (2010) and A. Sheykhi, Phys. Lett. B681, 205 (2009), we generalize their work to the new holographic dark energy model with [Formula: see text] in the framework of Brans–Dicke cosmology. Concretely, we study the correspondence between the quintessence, tachyon, K-essence, dilaton scalar field and Chaplygin gas model with the new holographic dark energy model in the non-flat Brans–Dicke universe. Furthermore, we reconstruct the potentials and dynamics for these models. By analysis we can show that for new holographic quintessence and Chaplygin gas models, if the related parameters to the potentials satisfy some constraints, the accelerated expansion can be achieved in Brans–Dicke cosmology. In particular, the counterparts of fields and potentials in general relativity can describe accelerated expansion of the universe. It is worth stressing that not only can we give some new results in the framework of Brans–Dicke cosmology, but also the previous results of the new holographic dark energy in Einstein gravity can be included as special cases given by us.

Viewing the Cosmological Consequences of Modified Holographic Dark Energy in Various Interaction Scenarios

2018 ◽  
Vol 73 (3) ◽  
pp. 251-257 ◽  
Author(s):  
Sthiti Chakrabarti ◽  
Surajit Chattopadhyay
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Scale Factor ◽  
Matter Density ◽  
Ricci Dark Energy ◽  
Dark Energy Density ◽  
Interaction Terms ◽  
Scale Factors ◽  
Phantom Phase

AbstractIn the work reported here, we have considered the interaction between modified holographic Ricci dark energy, a particular choice of Nojiri–Odintsov cut-offs, and pressureless dark matter for three different choices of scale factor, namely logamediate, intermediate, and emergent. Two different interaction terms have been considered. In one case, the interaction has been taken proportional to the dark energy density; in the other case, it has been taken proportional to the matter density. In the case of Q=3Hδρx, we have observed that there is a crossing of phantom boundary and the equation of state parameter has been observed to behave like quintessence. The influence of various parameters in the scale factors has also been observed. Also, an exit from phantom phase has been observed for the choice of scale factor in the emergent form. Considering the interaction term Q to be proportional to the matter density for logamediate scale factor, wx has been found to behave like quintessence, i.e. >−1. For the emergent scale factor in this interaction scenario, the model has been found to lead to a wx parameter lying in the region ≤−1. Therefore, in general, it has been found that Q=3Hδρx is more suitable than Q=3Hδρm in creating a model having a wx parameter crossing the phantom boundary.

Cosmological evolution of Tsallis holographic dark energy model in LTB inhomogeneous gravity

2020 ◽  
Vol 29 (03) ◽  
pp. 2050023 ◽  
Author(s):  
Ayman A. Aly ◽  
Mohammed Abd Elrashied ◽  
Mustafa M. Selim
Keyword(s):  
Dark Energy ◽  
Sound Speed ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Energy Conditions ◽  
Holographic Dark Energy Model ◽  
Inhomogeneous Models ◽  
Hubble Horizon ◽  
The Stability ◽  
The Universe

The aim of this work is to analyze the modified form of holographic dark energy (DE) density suggested by Tsallis and Cirto within inhomogeneous models of the universe. This DE model is applied to IR cutoff equals the Hubble horizon. Some basic cosmological functions, such as the Hubble function, the deceleration function and the equation of state parameter, are reconstructed by choosing specific values of certain numerical parameters in this model. The stability of the model is studied by considering the square of sound speed and the strong, the weak and the dominant energy conditions (DEC). In addition, the variation of the diagnostic Omega, [Formula: see text] and [Formula: see text] parameters with the redshift and space are studied. The obtained results show a close behavior to that of the cosmological constant DE universe so it can be compared well with the recent observations.

scholarly journals Generalization of the Randall-Sundrum Model Using Gravitational Model F(T,Θ)

2018 ◽  
Vol 2018 ◽  
pp. 1-5
Author(s):  
S. Davood Sadatian ◽  
S. M. Hosseini
Keyword(s):  
Dark Energy ◽  
Energy Momentum Tensor ◽  
State Parameter ◽  
Critical Value ◽  
Momentum Tensor ◽  
Generalized Model ◽  
Energy Models ◽  
Gravitational Model ◽  
Main Action ◽  
Two Parameters

In this letter, we explore a generalized model based on two scenarios including the Randall-Sundrum model and gravity model F(T,Θ). We first study the standard Randall-Sundrum gravitational model and then add a function containing two parameters as torsion and trace energy-momentum tensor to the main action of the model. Next, we derive the equations of the generalized model and obtain a new critical value for the energy density of the brane. The results showed that inflation and the dark energy-dominated stage can be realized in this model. We pointed out one significant category of dark energy models that had greatly developed the knowledge about dark energy. To be specific, dark energy could either be quintessence-like, phantom-like, or the so-called “quintom”-like. The models of quintom type suggest that the equation of state parameter of dark energy can cross the cosmological constant boundary ω=-1. Interestingly, this quintom scenario exactly appeared in this paper.

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