scholarly journals Ricci–Gauss–Bonnet holographic dark energy in Chern–Simons modified gravity: A flat FLRW quintessence-dominated universe

2019 ◽  
Vol 35 (05) ◽  
pp. 2050007 ◽  
Author(s):  
Nasr Ahmed
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Holographic Dark Energy ◽  
Cosmic Time ◽  
Early Time ◽  
State Parameter ◽  
Late Time ◽  
Equation Of State Parameter ◽  
Chern Simons ◽  
Far Future

We discuss the recently suggested Ricci–Gauss–Bonnet holographic dark energy in Chern–Simons modified gravity. We have tested some general forms of the scale factor [Formula: see text], and used two physically reasonable forms which have been proved to be consistent with observations. Both solutions predict a sign flipping in the evolution of cosmic pressure which is positive during the early-time deceleration and negative during the late-time acceleration. This sign flipping in the evolution of cosmic pressure helps in explaining the cosmic deceleration–acceleration transition, and it has appeared in other cosmological models in different contexts. However, this work shows a pressure singularity which needs to be explained. The evolution of the equation of state parameter [Formula: see text] shows the same asymptotic behavior for both solutions indicating a quintessence-dominated universe in the far future. We also note that [Formula: see text] goes to negative values (leaving the decelerating dust-dominated era at [Formula: see text]) at exactly the same time the pressure becomes negative. Again, there is another singularity in the behavior of [Formula: see text] which happens at the same cosmic time of the pressure singularity.

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.

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.

scholarly journals A reconstruction of modified holographic Ricci dark energy in f(R, T) gravity

2013 ◽  
Vol 91 (8) ◽  
pp. 632-638 ◽  
Author(s):  
Antonio Pasqua ◽  
Surajit Chattopadhyay ◽  
Iuliia Khomenko
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Cosmic Time ◽  
State Parameter ◽  
Diagnostic Analysis ◽  
Ricci Dark Energy ◽  
First Derivative ◽  
Proposed Model ◽  
Equation Of State Parameter ◽  
The Universe

In this paper, we consider a recently proposed model of dark energy (DE) know as modified holographic Ricci DE (which is function of the Hubble parameter and its first derivative with respect to cosmic time, t) in light of the f(R, T) model of modified gravity, considering the particular model f(R, T) = μR + νT, with μ and ν constants. The equation of state parameter ωΛ approaches but never reaches the value −1, implying a quintessence-like behavior of the model. The deceleration parameter q passes from decelerated to accelerated phase at a redshift of z ≈ 0.2, showing also a small dependence from the values of the parameters considered. Thanks to the statefinder diagnostic analysis, we observed that the ΛCDM phase for the considered model is attainable. We observed that the fractional energy densities for DE and dark matter, ΩΛ and Ωm, have an increasing and a decreasing pattern, respectively, with the evolution of the universe, indicating an evolution from matter to DE dominated universe. Finally, studying the squared speed of the sound [Formula: see text] for our model, we found that it is classically stable.

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 Accelerating cosmology in modified gravity: From convenient F(R) or string-inspired theory to bimetric F(R) gravity

2014 ◽  
Vol 11 (02) ◽  
pp. 1460006 ◽  
Author(s):  
Shin'ichi Nojiri ◽  
Sergei D. Odintsov
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Early Time ◽  
Cosmic Acceleration ◽  
Late Time ◽  
Reconstruction Method ◽  
Free Theory ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Unified Description

We consider modified gravity which may describe the early-time inflation and/or late-time cosmic acceleration of the universe. In particular, we discuss the properties of F(R), F(G), string-inspired and scalar-Einstein–Gauss–Bonnet gravities, including their FRW equations and fluid or scalar-tensor description. Simplest accelerating cosmologies are investigated and possibility of unified description of the inflation with dark energy is described. The cosmological reconstruction program which permits to get the requested universe evolution from modified gravity is developed. As some extension, massive F(R) bigravity which is ghost-free theory is presented. Its scalar-tensor form turns out to be the easiest formulation. The cosmological reconstruction method for such bigravity is presented. The unified description of inflation with dark energy in F(R) bigravity turns out to be possible.

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.

A study on the modified holographic Ricci dark energy in logarithmic f(T) gravity

2013 ◽  
Vol 91 (4) ◽  
pp. 351-354 ◽  
Author(s):  
Antonio Pasqua ◽  
Surajit Chattopadhyay
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Modified Gravity ◽  
State Parameter ◽  
Ricci Dark Energy ◽  
Equation Of State Parameter ◽  
Interaction Term ◽  
The Universe

In this paper, we have studied and investigated the behavior of a modified holographic Ricci dark energy (DE) model interacting with pressureless dark matter (DM) under the theory of modified gravity, dubbed logarithmic f(T) gravity. We have chosen the interaction term between DE and DM in the form Q = 3γHρm and investigated the behavior of the torsion, T, the Hubble parameter, H, the equation of state parameter, ωDE, the energy density of DE, ρDE, and the energy density contribution due to torsion, ρT, as functions of the redshift, z. We have found that T increases with the redshift, z, H increases with the evolution of the universe, ωDE has a quintessence-like behavior, and both energy densities increase going from higher to lower redshifts.

Comparing entropy inspired holographic dark energy models through statefinder hierarchy and growth rate of perturbations

2021 ◽  
Vol 18 (12) ◽  
Author(s):  
Mukesh Kumar ◽  
Vipin Chandra Dubey ◽  
Umesh Kumar Sharma
Keyword(s):  
Growth Rate ◽  
Dark Energy ◽  
Holographic Dark Energy ◽  
Growth Parameter ◽  
Early Time ◽  
Diagnostic Tools ◽  
Late Time ◽  
Energy Models ◽  
Evolutionary Trajectories ◽  
Different Characteristics

In this paper, we have investigated some recently proposed entropy-based versions of various HDE models, namely, the TADE, THDE, RHDE and SMHDE for different values of model parameter [Formula: see text] with the help of two diagnostic tools, in the context of a flat Friedmann–Lema[Formula: see text]tre–Robertson–Walker Universe. The statefinder hierarchy is the first diagnostic tool, by which we examine these DE models. The evolution of statefinder hierarchy parameters [Formula: see text], [Formula: see text] [Formula: see text], [Formula: see text] has been investigated by plotting against redshift [Formula: see text]. The evolutionary trajectories of all the DE models approach the [Formula: see text]CDM model, except the TADE model for some values of [Formula: see text] at late time, are well discriminated with the [Formula: see text]CDM model at early time. To get more clear discrimination among the DE models at late time, we have used the CND, i.e. [Formula: see text][Formula: see text], where [Formula: see text] indicates the fractional growth parameter. The evolutionary trajectories of [Formula: see text] and [Formula: see text] show different characteristics and the departure from [Formula: see text]CDM could be well evaluated.

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.

Cosmic aspects of chameleon Brans–Dicke gravity with parameterized deceleration parameters

2020 ◽  
Vol 17 (08) ◽  
pp. 2050115
Author(s):  
Abdul Jawad ◽  
Asma Aslam
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Vital Role ◽  
Cosmic Acceleration ◽  
Minimal Coupling ◽  
Frw Universe ◽  
Equation Of State Parameter

We investigate the chameleon Brans–Dicke gravity with new holographic dark energy which includes a non-minimal coupling between matter and scalar field. We use parameterized forms of deceleration parameter for flat FRW universe, which play a vital role to describe the nature of cosmic acceleration. We explore the cosmological parameters like Hubble parameter, equation of state parameter as well as its plane and stability of the obtained solution. The results of cosmological parameter and plane are consistent with observational data.

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