scholarly journals Interacting two-component fluid models with varying EoS parameter

2014 ◽  
Vol 11 (06) ◽  
pp. 1450061 ◽  
Author(s):  
M. Khurshudyan ◽  
B. Pourhassan ◽  
E. O. Kahya
Keyword(s):  
Dark Energy ◽  
Second Law Of Thermodynamics ◽  
Van Der Waals Gas ◽  
Eos Parameter ◽  
Barotropic Fluid ◽  
Ghost Dark Energy ◽  
Generalized Second Law ◽  
Two Component ◽  
Generalized Ghost Dark Energy ◽  
Total Fluid

In this paper, we consider Universe filled with two-component fluid. We study two different models. In the first model we assume barotropic fluid with the linear equation of state (EoS) as the first component of total fluid. In the second model we assume van der Waals gas as the first component of total fluid. In both models, the second component assumed generalized ghost dark energy. We consider also interaction between components and discuss, numerically, cosmological quantities for two different parametrizations of EoS which varies with time. We consider this as a toy model of our Universe. We fix parameters of the model by using generalized second law of thermodynamics. Comparing our results with some observational data suggests interacting barotropic fluid with EoS parameter [Formula: see text] and generalized ghost dark energy as an appropriate model to describe our Universe.

scholarly journals Phenomenologically varying Λ and a toy model for the universe

2014 ◽  
Vol 92 (11) ◽  
pp. 1494-1500 ◽  
Author(s):  
M. Khurshudyan ◽  
J. Sadeghi ◽  
E. Chubaryan ◽  
H. Farahani
Keyword(s):  
Dark Energy ◽  
Second Law Of Thermodynamics ◽  
Chaplygin Gas ◽  
Barotropic Fluid ◽  
Physical Conditions ◽  
Ghost Dark Energy ◽  
Generalized Second Law ◽  
Varying Λ ◽  
First Time ◽  
The Universe

We consider a model of the Universe with variable G and Λ. The subject of interest is a phenomenological model for Λ proposed and considered in this article for the first time (to our knowledge), with the assumption that ghost dark energy exists and interacts with the Universe through Λ. We consider the possibility that there exist unusual connections between different components of the fluids in Universe. We would like to stress that this is simply an assumption and could be very far from reality. This model is interesting phenomenologically and mathematically but we will not discuss physical conditions or possibilities of implementing the modifications. To test our assumption and to observe the behavior of the Universe, we will consider toy models filled by a barotropic fluid and modified Chaplyagin gas. Finally, we will consider interaction between barotropic fluid or Chaplygin gas and ghost dark energy as a separate scenario. The statefinder diagnostic provided stability analysis of the models. All free parameters of the model are fixed to satisfy the generalized second law of thermodynamics.

Entropy corrected holographic dark energy models in modified gravity

2017 ◽  
Vol 26 (04) ◽  
pp. 1750040 ◽  
Author(s):  
Abdul Jawad ◽  
Nadeem Azhar ◽  
Shamaila Rani
Keyword(s):  
Dark Energy ◽  
Modified Gravity ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Second Law Of Thermodynamics ◽  
Accelerated Expansion ◽  
Eos Parameter ◽  
Generalized Second Law ◽  
Expansion Of The Universe

We consider the power law and the entropy corrected holographic dark energy (HDE) models with Hubble horizon in the dynamical Chern–Simons modified gravity. We explore various cosmological parameters and planes in this framework. The Hubble parameter lies within the consistent range at the present and later epoch for both entropy corrected models. The deceleration parameter explains the accelerated expansion of the universe. The equation of state (EoS) parameter corresponds to quintessence and cold dark matter ([Formula: see text]CDM) limit. The [Formula: see text] approaches to [Formula: see text]CDM limit and freezing region in both entropy corrected models. The statefinder parameters are consistent with [Formula: see text]CDM limit and dark energy (DE) models. The generalized second law of thermodynamics remain valid in all cases of interacting parameter. It is interesting to mention here that our results of Hubble, EoS parameter and [Formula: see text] plane show consistency with the present observations like Planck, WP, BAO, [Formula: see text], SNLS and nine-year WMAP.

scholarly journals Interacting ghost dark energy models in the higher dimensional cosmology

2016 ◽  
Vol 25 (14) ◽  
pp. 1650108 ◽  
Author(s):  
J. Sadeghi ◽  
M. Khurshudyan ◽  
H. Farahani
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Eos Parameter ◽  
Barotropic Fluid ◽  
Ghost Dark Energy ◽  
Energy Models ◽  
Higher Dimensional Cosmology ◽  
Higher Dimensional ◽  
Interaction Term

We investigate interacting ghost dark energy models in higher dimensional cosmology. We attempt to model dark matter within a barotropic fluid with [Formula: see text]. In this work, we consider four different models based on choosing equation of state (EoS) parameter and interaction term. We confirm that our models agree with observational data.

Entropy and thermodynamics of ghost dark energy

2014 ◽  
Vol 92 (6) ◽  
pp. 529-532 ◽  
Author(s):  
Ahmad Sheykhi
Keyword(s):  
Dark Energy ◽  
Friedmann Equation ◽  
Additional Term ◽  
Second Law Of Thermodynamics ◽  
Late Time ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Generalized Second Law ◽  
System A ◽  
Hubble Horizon

We study the thermodynamics of the ghost model of dark energy in a flat Friedmann–Robertson–Walker (FRW) universe enveloped by a Hubble horizon. We show that the Friedmann equation of the FRW universe, in the presence of ghost dark energy, can be transformed to the first law of thermodynamics on the Hubble horizon. Using this procedure, we extract the entropy expression associated with the horizon in this model. We find that the area relation for the entropy expression is modified and an additional term that is proportional to the volume of the system, A3/2, appears in the entropy relation. We also find that for late time, where the temperature of the Universe scales as the temperature of its horizon, T = bTin, the generalized second law of thermodynamics can be secured provided 1/2 ≤ b ≤ 1, where T and Tin are the horizon and the matter fields’ temperatures, respectively.

scholarly journals Generalized ghost dark energy in DGP model

2019 ◽  
Vol 16 (11) ◽  
pp. 1950178
Author(s):  
Mahasweta Biswas ◽  
Ujjal Debnath ◽  
Shounak Ghosh
Keyword(s):  
Dark Energy ◽  
Sound Speed ◽  
Present Model ◽  
Cosmological Parameters ◽  
Current Phase ◽  
Eos Parameter ◽  
Ghost Dark Energy ◽  
Braneworld Model ◽  
The Universe ◽  
Generalized Ghost Dark Energy

In 2000, Dvali et al. [4-D gravity on a brane in 5-D Minkowski space, Phys. Lett. B 485 (2000) 208–214] proposed a new braneworld model named as DGP model, having two branches with [Formula: see text]. Former one [Formula: see text] known as accelerating branch, which explains accelerating phase of the Universe without adding cosmological constant or Dark energy (DE), whereas later one [Formula: see text] represents the decelerating branch. Here, we have investigated the behavior of Generalized Ghost Dark Energy (GGDE) under the decelerating branch of DGP model. We have studied the importance of GGDE model to explain the current phase of the Universe. To check the validity of the present model, we study the behavior of different cosmological parameters such as Hubble parameter, equation of state (EoS) parameter and deceleration parameter with respect to scale factor. Then, we have analyzed the [Formula: see text] to confirm no freezing region of this study and point out thawing region. Furthermore, we have checked the gradient of stability by calculating the squared sound speed. Then, we extend our study to check the viability of this model under investigation through the analysis of statefinder diagnosis parameters for the present cosmological setup.

scholarly journals Cosmology of Barrow Holographic Dark Energy as Nojiri-Odintsov Holographic Dark Energy with Specific Cut-off and the Thermodynamics

2021 ◽  
Author(s):  
Gargee Chakraborty ◽  
Surajit Chattopadhyay ◽  
Ertan Güdekli ◽  
Irina Radinschi
Keyword(s):  
Phase Transition ◽  
Dark Energy ◽  
Holographic Dark Energy ◽  
Second Law Of Thermodynamics ◽  
Electroweak Symmetry Breaking ◽  
Second Law ◽  
Late Time ◽  
Electroweak Symmetry ◽  
Eos Parameter ◽  
Reconstruction Scheme

Motivated by the work of Saridakis (Phys. Rev. D 102, 123525 (2020)), the present study reports the cosmological consequences of Barrow holographic dark energy (HDE) and its thermodynamics. Literatures demonstrate that Dark Energy (DE) may result from electroweak symmetry breaking that triggers a phase transition from early inflation to late time acceleration. In the present study, we incorporated viscosity in the Barrow HDE. A reconstruction scheme is presented for the parameters associated with Barrow holographic dark energy under the purview of viscous cosmology. Equation of state (EoS) parameter is reconstructed in this scenario and quintessence behaviour is observed. Considering BarrowHDE as a specific case ofNojiri-Odintsov (NO) HDE, we have observed quintom behaviour of the EoS parameter and for some values of n the EoS has been observed to be very close to −1 for the current universe. The generalised second law of thermodynamics has come out to be valid in all the scenarios under consideration. Physical viability of considering Barrow HDE as a specific case of NO HDE is demonstrated in this study.

scholarly journals Study of QCD generalized ghost dark energy in FRW universe

2019 ◽  
Vol 79 (8) ◽  
Author(s):  
Mahasweta Biswas ◽  
Ujjal Debnath ◽  
Shounak Ghosh ◽  
B. K. Guha
Keyword(s):  
Dark Energy ◽  
Frw Universe ◽  
Ghost Dark Energy ◽  
Generalized Ghost Dark Energy

Analysis of cubic gravity through cosmic aspects

2020 ◽  
Vol 17 (09) ◽  
pp. 2050134 ◽  
Author(s):  
Zoya Khan ◽  
Shamaila Rani ◽  
Abdul Jawad ◽  
G. Mustafa
Keyword(s):  
Hubble Parameter ◽  
Thermal Equilibrium ◽  
Equilibrium Condition ◽  
Cosmological Parameters ◽  
Second Law Of Thermodynamics ◽  
Observational Constraints ◽  
Eos Parameter ◽  
Generalized Second Law ◽  
Thermal Equilibrium Condition ◽  
Almost All

In the context of cubic gravity for flat FRW metric we discuss the behavior of cosmological parameters (equation of state (EoS) parameter and square speed of sound) at Hubble horizon with the four different models of Hubble parameter. We observe the validity of generalized second law of thermodynamics (GSLT) and thermal equilibrium condition. It is found that cosmological parameters lie within the observational constraints. Also, GSLT and thermal equilibrium condition holds in almost all cases of Hubble parameter.

scholarly journals VISCOUS DARK ENERGY AND GENERALIZED SECOND LAW OF THERMODYNAMICS

2010 ◽  
Vol 19 (07) ◽  
pp. 1205-1215 ◽  
Author(s):  
M. R. SETARE ◽  
A. SHEYKHI
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Time Evolution ◽  
Casimir Effect ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Total Entropy ◽  
Generalized Second Law ◽  
The Universe

We examine the validity of the generalized second law of thermodynamics in a non-flat universe in the presence of viscous dark energy. First we assume that the universe is filled only with viscous dark energy. Then, we extend our study to the case where there is an interaction between viscous dark energy and pressureless dark matter. We examine the time evolution of the total entropy, including the entropy associated with the apparent horizon and the entropy of the viscous dark energy inside the apparent horizon. Our study shows that the generalized second law of thermodynamics is always protected in a universe filled with interacting viscous dark energy and dark matter in a region enclosed by the apparent horizon. Finally, we show that the the generalized second law of thermodynamics is fulfilled for a universe filled with interacting viscous dark energy and dark matter by taking into account the Casimir effect.

scholarly journals THERMODYNAMICS IN KALUZA–KLEIN UNIVERSE

2013 ◽  
Vol 28 (17) ◽  
pp. 1350072 ◽  
Author(s):  
M. SHARIF ◽  
RABIA SALEEM
Keyword(s):  
Dark Energy ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Model Parameters ◽  
Ricci Dark Energy ◽  
Generalized Second Law ◽  
Energy Models ◽  
Fixed Radius ◽  
Kaluza Klein

This paper is devoted to check the validity of laws of thermodynamics for Kaluza–Klein universe in the state of thermal equilibrium, composed of dark matter and dark energy. The generalized holographic dark energy and generalized Ricci dark energy models are considered here. It is proved that the first and generalized second law of thermodynamics are valid on the apparent horizon for both of these models. Further, we take a horizon of radius L with modified holographic or Ricci dark energy. We conclude that these models do not obey the first and generalized second law of thermodynamics on the horizon of fixed radius L for a specific range of model parameters.

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