scholarly journals THERMODYNAMICAL PROPERTIES OF DARK ENERGY IN LOOP QUANTUM COSMOLOGY

2011 ◽  
Vol 20 (02) ◽  
pp. 169-179
Author(s):  
KUI XIAO ◽  
JIAN-YANG ZHU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Quantum Cosmology ◽  
Thermal Equilibrium ◽  
Apparent Horizon ◽  
State Parameter ◽  
Loop Quantum Cosmology ◽  
Thermodynamical Properties ◽  
The One ◽  
Modified Entropy

Considering an arbitrary, varying equation of state parameter, the thermodynamical properties of dark energy fluid in the semiclassical loop quantum cosmology scenario, where we consider the inverse volume modification, are studied. The equation of state parameters are corrected when we consider the effective behavior. Assuming that the apparent horizon has Hawking temperature, the modified entropy–area relation is obtained, and we find that this relation is different from the one which is obtained by considering the holonomy correction. Considering that the dark energy is in thermal equilibrium with the Hawking radiation of the apparent horizon, we get the expression for the entropy of the dark energy fluid.

scholarly journals Tsallis, Rényi and Sharma-Mittal Holographic Dark Energy Models in Loop Quantum Cosmology

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 635 ◽  
Author(s):  
Abdul Jawad ◽  
Kazuharu Bamba ◽  
Muhammad Younas ◽  
Saba Qummer ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Quantum Cosmology ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
State Parameter ◽  
Loop Quantum Cosmology ◽  
Eos Parameter ◽  
Energy Models ◽  
The Universe

The cosmic expansion phenomenon is being studied through the interaction of newly proposed dark energy models (Tsallis, Rényi and Sharma-Mittal holographic dark energy (HDE) models) with cold dark matter in the framework of loop quantum cosmology. We investigate different cosmic implications such as equation of state parameter, squared sound speed and cosmological plane (ω d - ω d ′ , ω d and ω d ′ represent the equation of state (EoS) parameter and its evolution, respectively). It is found that EoS parameter exhibits quintom like behavior of the universe for all three models of HDE. The squared speed of sound represents the stable behavior of Rényi HDE and Sharma-Mittal HDE at the latter epoch while unstable behavior for Tsallis HDE. Moreover, ω d - ω d ′ plane lies in the thawing region for all three HDE models.

VALIDITY OF THE THERMODYNAMICAL PROPERTIES OF THE DARK ENERGY MODEL WITH THE EQUATION OF STATE: w = w0 + w1 · z(1 + z)/(1 + z2)

2011 ◽  
Vol 26 (12) ◽  
pp. 885-892 ◽  
Author(s):  
LILI XING ◽  
JIANBIN CHEN ◽  
YUANXING GUI ◽  
ERIC M. SCHLEGEL ◽  
JIANBO LU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Event Horizon ◽  
Dark Energy Model ◽  
Apparent Horizon ◽  
Parametric Model ◽  
Isotropic Universe ◽  
Thermodynamical Properties ◽  
Spatially Homogeneous ◽  
The Universe

We investigate the validity of the thermodynamical properties of the universe in a new parametric model of dark energy with the equation of state w = w0 + w1 · z(1 + z)/(1 + z2). In the spatially homogeneous and isotropic universe, assuming that the temperature and entropy in cosmology is as in a black hole, we examine the thermodynamical properties of the universe bounded by the apparent horizon and the event horizon respectively. By analysis, we find that the first and the second laws of thermodynamics are valid inside the apparent horizon, while they break down inside the event horizon.

Non-flat FRW universe version of Tsallis holographic dark energy in specific modified gravity

2019 ◽  
Vol 34 (07n08) ◽  
pp. 1950055 ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Nadeem Azhar
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Modified Gravity ◽  
Holographic Dark Energy ◽  
Apparent Horizon ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Frw Universe ◽  
Generalized Second Law ◽  
The Stability

Among various dark energy models, Tsallis holographic dark energy model shows the dynamical enthusiasm to describe the transition phase of the universe. In this paper, we consider Tsallis holographic dark energy with event and apparent horizon as an infrared cutoff in the framework of dynamical Chern–Simon modified gravity and non-flat FRW universe. We explore Hubble, equation of state and deceleration parameters and found that Hubble parameter lies in the range [Formula: see text] and [Formula: see text] for event and apparent horizon trajectories, respectively. It is mentioned here that the equation of state parameter lies within the range [Formula: see text] (event) and [Formula: see text] (apparent). Also, deceleration parameter for both cases show accelerated and decelerated phase of universe as well as cosmological constant. Moreover, we also checked the stability of our model through square speed of sound, which shows the positive behavior (exhibits the stability of the model). Finally, we observe that the generalized second law of thermodynamics remains valid in both cases of horizon.

FRW viscous fluid cosmological model with time-dependent inhomogeneous equation of state

2017 ◽  
Vol 15 (01) ◽  
pp. 1830001 ◽  
Author(s):  
G. S. Khadekar ◽  
Deepti Raut
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Quadratic Form ◽  
State Parameter ◽  
The Other ◽  
Time Dependent ◽  
Inhomogeneous Equation ◽  
Field Equations ◽  
Equation Of State Parameter ◽  
Viscous Models

In this paper, we present two viscous models of non-perfect fluid by avoiding the introduction of exotic dark energy. We consider the first model in terms of deceleration parameter [Formula: see text] has a viscosity of the form [Formula: see text] and the other model in quadratic form of [Formula: see text] of the type [Formula: see text]. In this framework we find the solutions of field equations by using inhomogeneous equation of state of form [Formula: see text] with equation of state parameter [Formula: see text] is constant and [Formula: see text].

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 Reheating constraints on Kähler moduli inflation

2019 ◽  
Vol 34 (15) ◽  
pp. 1950114 ◽  
Author(s):  
Rakesh Kabir ◽  
Amitabha Mukherjee ◽  
Daksh Lohiya
Keyword(s):  
Equation Of State ◽  
State Parameter ◽  
Index Formula ◽  
Planck Data ◽  
Slow Roll ◽  
Cosmological Scenario ◽  
Hubble Radius ◽  
The One ◽  
Potential Parameters ◽  
The Universe

The end of inflation is connected to the standard cosmological scenario through reheating. During reheating, the inflaton oscillates around the minimum of the potential and thus decays into the daughter particles that populate the Universe at later times. Using cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time, we translate the constraint on the spectral index [Formula: see text] from Planck data to the constraint on the reheating scenario in the context of Kähler moduli inflation. We find that the equation of state parameter plays a crucial role in the reheating analysis, however the details of the one parameter potential are irrelevant if the analysis is done strictly within the slow-roll formalism. In addition, we extend the de facto analysis generally done only for the pivot scale to all the observable scales which crossed the Hubble radius during inflation, where we study how the maximum number of e-folds varies for different scales, and the effect of the equation of state and potential parameters.

scholarly journals BRANE–BULK ENERGY EXCHANGE AND AGEGRAPHIC DARK ENERGY

2010 ◽  
Vol 19 (03) ◽  
pp. 305-316 ◽  
Author(s):  
AHMAD SHEYKHI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Normal State ◽  
Energy Exchange ◽  
State Parameter ◽  
Effective Equation ◽  
Agegraphic Dark Energy ◽  
Equation Of State Parameter ◽  
Bulk Energy

We consider the agegraphic models of dark energy in a braneworld scenario with brane–bulk energy exchange. We assume that the adiabatic equation for the dark matter is satisfied while it is violated for the agegraphic dark energy due to the energy exchange between the brane and the bulk. Our study shows that with the brane–bulk interaction, the equation of state parameter of agegraphic dark energy on the brane, wD, can have a transition from the normal state, where wD > -1, to the phantom regime, where wD < -1, while the effective equation of state for dark energy always satisfies [Formula: see text].

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