scholarly journals Thermodynamic Implications of Multiquintessence Scenario

Entropy ◽  
2019 ◽  
Vol 21 (9) ◽  
pp. 851 ◽  
Author(s):  
Abdul Jawad ◽  
Zoya Khan ◽  
Shamaila Rani ◽  
Kazuharu Bamba
Keyword(s):  
Hubble Parameter ◽  
Thermal Equilibrium ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Frw Universe ◽  
Equilibrium Conditions ◽  
Potential Models ◽  
First Order ◽  
Generalized Second Law ◽  
Friedmann Robertson Walker

In this paper, we discuss the validity of the generalized second law of thermodynamics in the presence of a multi-component scalar field ( ϕ ) in a spatially flat Friedmann-Robertson-Walker (FRW) universe. We describe the first-order formalism by defining the Hubble parameter as H = - W ( ϕ i ) . By using three super-potential models of the Hubble parameter, we analyze the validity of the generalized law and thermal equilibrium conditions in the presence of the logarithmically-corrected, Bekenstein-Hawking, Sharma-Mittal and R e ´ n y i entropies. It is noticed that the generalized law and thermal equilibrium conditions hold for some cases.

A unified picture of cosmological entropy on apparent horizon in F(R, G) gravity

2017 ◽  
Vol 32 (33) ◽  
pp. 1750182 ◽  
Author(s):  
Ali İhsan Keskin ◽  
Irfan Acikgoz
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Hawking Temperature ◽  
Second Law ◽  
Field Equations ◽  
Frw Universe ◽  
Generalized Second Law ◽  
History Of ◽  
The Universe ◽  
Friedmann Robertson Walker

In this study, the validity of the generalized second law of thermodynamics (GSLT) has been investigated in F(R, G) gravity. We consider that the boundary of the universe is surrounded by an apparent horizon in the spatially flat Friedmann–Robertson–Walker (FRW) universe, and we take into account the Hawking temperature on the horizons. The unified solutions of the field equations corresponding to gravity theory have been applied to the validity of the GSLT frame, and in this way, both the solutions have been verified and all the expansion history of the universe has been shown in a unified picture.

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 Thermodynamics of Ricci-Gauss-Bonnet Dark Energy

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Ayesha Iqbal ◽  
Abdul Jawad
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Cold Dark Matter ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Frw Universe ◽  
Thermodynamical Equilibrium ◽  
Event Horizons ◽  
Generalized Second Law ◽  
Friedmann Robertson Walker

We investigate the validity of generalized second law of thermodynamics of a physical system comprising newly proposed dark energy model called Ricci-Gauss-Bonnet and cold dark matter enveloped by apparent horizon and event horizon in flat Friedmann-Robertson-Walker (FRW) universe. For this purpose, Bekenstein entropy, Renyi entropy, logarithmic entropy, and power law entropic corrections are used. It is found that this law exhibits the validity on both apparent and event horizons except for the case of logarithmic entropic correction at apparent horizon. Also, we check the thermodynamical equilibrium condition for all cases of entropy and found its vitality in all cases of entropy.

Thermodynamics of apparent horizon in mimetic cosmology

2019 ◽  
Vol 28 (03) ◽  
pp. 1950057 ◽  
Author(s):  
Ahmad Sheykhi
Keyword(s):  
Apparent Horizon ◽  
Local Equilibrium ◽  
Second Law Of Thermodynamics ◽  
High Energy ◽  
Frw Universe ◽  
Generalized Second Law ◽  
Friedmann Equations ◽  
New Perspective ◽  
Friedmann Robertson Walker ◽  
Mimetic Gravity

A new perspective toward Einstein’s theory of general relativity, called mimetic gravity, was suggested in [A. H. Chamseddine and V. Mukhanov, J. High Energy Phys. 1311 (2013) 135] by isolating the conformal degree of freedom in a covariant fashion through a re-parametrization of the physical metric in terms of an auxiliary metric and a mimetic field. In this paper, we first derive the Friedmann equations of the Friedmann–Robertson–Walker (FRW) universe with any spatial curvature in mimetic gravity. Then, we disclose that one can always rewrite the Friedmann equations of mimetic cosmology in the form of the first law of thermodynamics, [Formula: see text], on the apparent horizon. We confirm that the entropy associated with the apparent horizon in mimetic cosmology still obeys the area law of entropy which is useful in studying the thermodynamical properties of the black holes in mimetic gravity. We also examine the time evolution of the total entropy in mimetic cosmology and show that, with the local equilibrium assumption, the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon. Our study further supports the viability of the mimetic gravity from a thermodynamic viewpoint and provides a strong consistency check of this model.

scholarly journals Generalized second law of thermodynamics in the presence of interacting tachyonic field and scalar (phantom) field

2010 ◽  
Vol 88 (12) ◽  
pp. 933-938 ◽  
Author(s):  
Surajit Chattopadhyay ◽  
Ujjal Debnath
Keyword(s):  
Scalar Field ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Frw Universe ◽  
Tachyonic Field ◽  
Phantom Field ◽  
Generalized Second Law

In the present work, we consider the tachyonic field, the phantom field, and the scalar field in both interacting and non-interacting situations and investigate the validity of the generalized second law of thermodynamics in a flat FRW universe. We find that in all cases, except for the phantom field dominated universe, the derivative of the entropy remains at negative level and increases with the decrease in redshift.

scholarly journals Qualitative aspects of Rastall gravity with barotropic fluid

2021 ◽  
Author(s):  
Ashutosh Singh ◽  
Rakesh Raushan ◽  
R. Chaubey
Keyword(s):  
Dynamical System ◽  
Equation Of State ◽  
System Approach ◽  
Apparent Horizon ◽  
Dynamical Evolution ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Frw Universe ◽  
Barotropic Fluid ◽  
Generalized Second Law

We investigate the dynamical evolution of homogeneous and isotropic flat-FRW universe filled with a barotropic fluid satisfying linear equation of state in Rastall gravity. Using dynamical system approach, we find the fixed points of the system and study their stability. We further explore the thermodynamic aspects at the apparent horizon by investigating the validity of generalized second law of thermodynamics with equilibrium description.

scholarly journals Holographic dark energy and generalized second law

2014 ◽  
Vol 29 (06) ◽  
pp. 1450023 ◽  
Author(s):  
Titus K. Mathew ◽  
P. Praseetha
Keyword(s):  
Dark Energy ◽  
Event Horizon ◽  
Holographic Dark Energy ◽  
Apparent Horizon ◽  
Second Law ◽  
Frw Universe ◽  
Equilibrium Conditions ◽  
Generalized Second Law ◽  
Horizon Entropy ◽  
Non Equilibrium

We explore the validity of the generalized second law (GSL) of thermodynamics in flat FRW universe with apparent horizon and event horizon as the boundary. We found that in a universe with holographic dark energy and dark matter, interacting with each other, the GSL is satisfied at the apparent horizon and partially satisfied at the event horizon under thermal equilibrium conditions. We also analyzed the GSL under non-equilibrium conditions and shows that the fulfillment of GSL at the apparent horizon implies that the temperature of the dark energy is greater than that of the horizon. Thus, there occurs a flow of dark energy towards the apparent horizon. As a result, the entropy of the dark energy decreases and that of the horizon increases. This is verified by finding the evolution of the dark energy entropy and horizon entropy in a dark energy dominated universe under non-equilibrium conditions.

Thermodynamics of squared speed of sound parametrizations

2020 ◽  
Vol 17 (05) ◽  
pp. 2050072
Author(s):  
Abdul Jawad ◽  
Sadaf Butt ◽  
Aneesa Majeed
Keyword(s):  
Thermodynamic Equilibrium ◽  
Speed Of Sound ◽  
Thermal Equilibrium ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Order ◽  
Second Law ◽  
Total Entropy ◽  
Generalized Second Law

In this work, an attempt is made to study the thermodynamical analysis at the apparent horizon in the framework of fractal universe. We consider the Bekenstein entropy to examine validity of the generalized second law of thermodynamics (GSLT) and thermal equilibrium for the four different cases which are developed with the utilization of different forms of squared speed of sound. In each case, we explore the behavior of total entropy through the graphical variation of its first- and second-order derivatives with respect to redshift parameter ([Formula: see text]). It is found that generalized second law of thermodynamics holds for Cases 1 and 2 for [Formula: see text] and [Formula: see text], respectively and it holds in late times as well. However, for Cases [Formula: see text] and [Formula: see text], this law is satisfied in early, present and future epochs. Furthermore, for Cases 1 and 2, instability of thermodynamic equilibrium is observed, but for Cases 3 and 4, it holds in the specific intervals [Formula: see text] and [Formula: see text], respectively.

scholarly journals The generalized second law of thermodynamics for interacting f(R) gravity

2014 ◽  
Vol 23 (08) ◽  
pp. 1450071 ◽  
Author(s):  
Ramón Herrera ◽  
Nelson Videla
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Effective Equation ◽  
Frw Universe ◽  
Total Energy Density ◽  
Generalized Second Law ◽  
Interaction Term ◽  
The Universe ◽  
Gravitational Thermodynamics

In this paper, we examine the validity of the generalized second law (GSL) of gravitational thermodynamics in the context of interacting f(R) gravity. We take into account that the boundary of the universe to be confined by the dynamical apparent horizon in a flat FRW universe. We study the effective equation of state, deceleration parameter and GSL in this interaction-framework. We find that the evolution of the total entropy increases through the interaction term. As an example, we consider a f(R) gravity with a power-law dependence on the curvature R. Here, we find exact solutions for a model in which the interaction term is related to the total energy density of matter.

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