scholarly journals Interacting holographic dark energy model in Brans–Dicke cosmology and coincidence problem

2018 ◽  
Vol 27 (03) ◽  
pp. 1850017 ◽  
Author(s):  
F. Felegary ◽  
F. Darabi ◽  
M. R. Setare
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Holographic Dark Energy Model ◽  
Future Event ◽  
Coincidence Problem ◽  
The Future ◽  
Hubble Horizon ◽  
Future Event Horizon

We study the dynamics of interacting holographic dark energy model in Brans–Dicke cosmology for the future event horizon and the Hubble horizon cut-offs. We determine the system of first-order differential equations for the future event horizon and Hubble horizon cut-offs and obtain the corresponding fixed points, attractors, repellers and saddle points. Finally, we investigate the cosmic coincidence problem in this model for the future event horizon and Hubble horizon cut-offs and find that for both cut-offs and for a variety of Brans–Dicke parameters, the coincidence problem is almost resolved.

scholarly journals DARK ENERGY AND THE FUTURE FATE OF THE UNIVERSE

2007 ◽  
Vol 22 (35) ◽  
pp. 2689-2699
Author(s):  
YUNGUI GONG ◽  
YUAN-ZHONG ZHANG
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Scale Factor ◽  
Energy Model ◽  
Holographic Dark Energy Model ◽  
Hubble Horizon ◽  
Size Criterion ◽  
The Universe

We consider the possibility of observing the onset of the late time inflation of our patch of the Universe. The Hubble size criterion and the event horizon criterion are applied to several dark energy models to discuss the problem of future inflation of the Universe. We find that the acceleration has not lasted long enough to confirm the onset of inflation by present observations for the dark energy model with constant equation of state, the holographic dark energy model and the generalized Chaplygin gas (GCG) model. For the flat ΛCDM model with Ωm0 = 0.3, we find that if we use the Hubble size criterion, we need to wait until the av which is the scale factor at the time when the onset of inflation is observed reaches 3.59 times of the scale factor aT when the Universe started acceleration, and we need to wait until av = 2.3aT to see the onset of inflation if we use the event horizon criterion. For the flat holographic dark energy model with d = 1, we find that av = 3.46aT with the Hubble horizon and av = 2.34aT with the event horizon, respectively. For the flat GCG model with the best supernova fitting parameter α = 1.2, we find that av = 5.50aT with the Hubble horizon and av = 2.08aT with the event horizon, respectively.

scholarly journals Holographic dark energy with the sign-changeable interaction term

2017 ◽  
Vol 26 (08) ◽  
pp. 1750080 ◽  
Author(s):  
M. Abdollahi Zadeh ◽  
A. Sheykhi ◽  
H. Moradpour
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Holographic Dark Energy ◽  
Late Time ◽  
Coupling Constant ◽  
Future Event ◽  
Frw Universe ◽  
Eos Parameter ◽  
The Future ◽  
Future Event Horizon

We use three infrared (IR) cutoffs, including the future event horizon, the Hubble and Granda–Oliveros (GO) cutoffs, to construct three holographic models of dark energy (DE). Additionally, we consider a Friedmann–Robertson–Walker (FRW) universe filled by a dark matter (DM) and a DE that interact with each other through a mutual sign-changeable interaction with positive coupling constant. Thereinafter, we address the evolution of the some cosmological parameters, such as the equation of state (EoS) and dimensionless density parameters of DE as well as the deceleration parameter, during the cosmic evolution from the matter-dominated era until the late-time acceleration. We observe that a holographic dark energy (HDE) model with Hubble cutoff interacting with DM cannot be in line with the current universe. Our study shows that models with the future event horizon as the IR cutoff or the GO cutoff are in good agreement with the observational data. In fact, we find out that these two recent models can predict the universe transition from a deceleration phase to the acceleration one in a compatible way with observations. The three obtained models may also allow the EoS parameter to cross the phantom line, a result which depends on the values of the system’s constants such as the value of the interaction coupling constant.

scholarly journals A TRACKER SOLUTION FOR A HOLOGRAPHIC DARK ENERGY MODEL

2006 ◽  
Vol 15 (06) ◽  
pp. 869-877 ◽  
Author(s):  
HUI LI ◽  
ZONG-KUAN GUO ◽  
YUAN-ZHONG ZHANG
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Energy Model ◽  
Holographic Dark Energy Model ◽  
Coincidence Problem ◽  
Accelerating Expansion ◽  
State 1

We investigate a kind of holographic dark energy model with a future event horizon being IR cutoff and the equation of state -1. In this model, the constraint on the equation of state automatically specifies an interaction between matter and dark energy. With this interaction included, an accelerating expansion is obtained as well as the transition from deceleration to acceleration. It is found that there exists a stable tracker solution for the numerical parameter d > 1, and d smaller than one will not lead to a physical solution. This model provides another possible phenomenological framework to alleviate the cosmological coincidence problem in the context of holographic dark energy. Some properties of the evolution which are relevant to cosmological parameters are also discussed.

scholarly journals (m, n)-TYPE HOLOGRAPHIC DARK ENERGY MODELS

2013 ◽  
Vol 28 (31) ◽  
pp. 1350128 ◽  
Author(s):  
YI LING ◽  
WEN-JIAN PAN
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Holographic Dark Energy ◽  
Characteristic Size ◽  
Scalar Perturbation ◽  
Future Event ◽  
Energy Models ◽  
The Stability ◽  
Phantom Phase ◽  
Future Event Horizon

We construct (m, n)-type holographic dark energy models at a phenomenological level, which can be viewed as a generalization of agegraphic models with the conformal-like age as the holographic characteristic size. For some values of (m, n) the holographic dark energy can automatically evolve across ω = -1 into a phantom phase even without introducing an interaction between the dark energy and background matter. Our construction is also applicable to the holographic dark energy with generalized future event horizon as the characteristic size. Finally, we address the issue on the stability of our model and show that they are generally stable under the scalar perturbation.

scholarly journals A cosmographic analysis of holographic dark energy models

2014 ◽  
Vol 23 (11) ◽  
pp. 1450092 ◽  
Author(s):  
Supriya Pan ◽  
Subenoy Chakraborty
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Dark Energy Model ◽  
Holographic Dark Energy ◽  
Energy Model ◽  
Length Scale ◽  
Holographic Dark Energy Model ◽  
Energy Models ◽  
Interaction Term

The present work deals with a detailed study of interacting holographic dark energy model for three common choices of the interaction term. Also, two standard choices of IR cut-off, namely, Ricci length scale and radius of the event horizon are considered here. Finally, the cosmographic parameters are presented both analytically and graphically.

scholarly journals Sign-changeable holographic dark energy in Brans–Dicke theory

2019 ◽  
Vol 97 (7) ◽  
pp. 726-734 ◽  
Author(s):  
M. Abdollahi Zadeh ◽  
A. Sheykhi
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Holographic Dark Energy ◽  
Model Parameters ◽  
Density Parameter ◽  
Future Event ◽  
Frw Universe ◽  
Eos Parameter ◽  
The Stability ◽  
Future Event Horizon

We consider the Brans–Dicke (BD) theory of gravity and explore the cosmological implications of the sign-changeable interacting holographic dark energy (HDE) model in the background of a Friedmann–Robertson–Walker (FRW) universe. As the system’s infrared cutoff, we choose the future event horizon, the Granda–Oliveros (GO), and the Ricci cutoffs. For each cutoff, we obtain the density parameter, the equation of state (EoS), and the deceleration parameter of the system. In case of future event horizon, we find out that the EoS parameter, wD, can cross the phantom line; as a result the transition from the deceleration to the acceleration of the Universe expansion can be achieved provided the model parameters are chosen suitably. We also investigate the instability of the sign-changeable interacting HDE model against perturbations in BD theory. For this purpose, we study the squared sound speed [Formula: see text] whose sign determines the stability of the model. When [Formula: see text] the model is unstable against perturbation. For future event horizon, our Universe can be stable ([Formula: see text]) depending on the model parameters. Then, we focus on GO and Ricci cutoffs and find out that although other features of these two cutoffs are consistent with observations, they cannot lead to stable dominated universe, except in a special case with GO cutoff. Our studies confirm that for the sign-changeable HDE model in the setup of BD cosmology, the event horizon is the most suitable horizon that can pass all conditions and leads to a stable dark-energy-dominated universe.

Analysis of interacting entropy-corrected holographic and new agegraphic dark energies

2018 ◽  
Vol 27 (04) ◽  
pp. 1850035
Author(s):  
Chayan Ranjit ◽  
Ujjal Debnath
Keyword(s):  
Dark Energy ◽  
Text Analysis ◽  
Dark Energy Model ◽  
Length Scale ◽  
Logarithmic Correction ◽  
Future Event ◽  
Frw Model ◽  
Hubble Horizon ◽  
The Universe ◽  
Future Event Horizon

In the present work, we assume the flat FRW model of the universe is filled with dark matter and dark energy where they are interacting. For dark energy model, we consider the entropy-corrected HDE (ECHDE) model and the entropy-corrected NADE (ECNADE). For entropy-corrected models, we assume logarithmic correction and power law correction. For ECHDE model, length scale [Formula: see text] is assumed to be Hubble horizon and future event horizon. The [Formula: see text]-[Formula: see text] analysis for our different horizons are discussed.

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