scholarly journals Thermodynamics in f(G,T) Gravity

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
M. Sharif ◽  
Ayesha Ikram
Keyword(s):  
Energy Momentum Tensor ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Second Law ◽  
De Sitter ◽  
Field Equations ◽  
Generalized Second Law ◽  
Homogeneous Universe ◽  
Free Parameters

This paper explores the nonequilibrium behavior of thermodynamics at the apparent horizon of isotropic and homogeneous universe model in f(G,T) gravity (G and T represent the Gauss-Bonnet invariant and trace of the energy-momentum tensor, resp.). We construct the corresponding field equations and analyze the first as well as generalized second law of thermodynamics in this scenario. It is found that an auxiliary term corresponding to entropy production appears due to the nonequilibrium picture of thermodynamics in first law. The universal condition for the validity of generalized second law of thermodynamics is also obtained. Finally, we check the validity of generalized second law of thermodynamics for the reconstructed f(G,T) models (de Sitter and power-law solutions). We conclude that this law holds for suitable choices of free parameters.

The wormhole thermodynamics in f (R ) gravity

2019 ◽  
Vol 35 (04) ◽  
pp. 1950360 ◽  
Author(s):  
A. S. Sefiedgar ◽  
M. Mirzazadeh
Keyword(s):  
Continuity Equation ◽  
Energy Momentum Tensor ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Second Law ◽  
Standard Entropy ◽  
Field Equations ◽  
First Law Of Thermodynamics ◽  
Generalized Second Law

Thermodynamics of the evolving Lorentzian wormhole at the apparent horizon is investigated in [Formula: see text] gravity. Redefining the energy density and the pressure, the continuity equation is satisfied and the field equations in [Formula: see text] gravity reduce to the ones in general relativity. However, the energy–momentum tensor includes all the corrections from [Formula: see text] gravity. Therefore, one can apply the standard entropy-area relation within [Formula: see text] gravity. It is shown that there may be an equivalency between the field equations and the first law of thermodynamics. It seems that an equilibrium thermodynamics may be held on the apparent horizon. The validity of the generalized second law of thermodynamics (GSL) is also investigated in the wormholes.

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.

scholarly journals Study of GSLT in Curvature-Matter Coupling Gravity

2018 ◽  
Vol 168 ◽  
pp. 03007
Author(s):  
Muhammad Sharif ◽  
Ayesha Ikram
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Universe Model ◽  
Field Equations ◽  
Isotropic Universe ◽  
Matter Coupling ◽  
Generalized Second Law ◽  
Energymomentum Tensor ◽  
Laws Of Thermodynamics

In this work, we study the first and generalized second laws of thermodynamics at the apparent horizon of homogeneous and isotropic universe model in the context of f (G, T) gravity (G and T represent the Gauss-Bonnet invariant and trace of the energymomentum tensor, respectively). We formulate the corresponding field equations as well as determine the radius, temperature and entropy to analyze these laws. An extra term associated with entropy production is appeared in the first law due to the non-equilibrium treatment of thermodynamics. It is found that the universal condition is obtained to preserve the generalized second law of thermodynamics.

Thermodynamic consequences of specific modified gravity on the apparent horizon

2019 ◽  
Vol 16 (09) ◽  
pp. 1950144
Author(s):  
Abdul Jawad ◽  
Zoya Khan ◽  
Shamaila Rani
Keyword(s):  
Scalar Field ◽  
Modified Gravity ◽  
Energy Momentum Tensor ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Isotropic Universe ◽  
First Order ◽  
Generalized Second Law ◽  
Thermodynamical Behavior

We discuss the thermodynamical behavior of homogeneous and isotropic universe (flat and non-flat) in the framework of [Formula: see text] gravity, where [Formula: see text] stands for Ricci scalar and [Formula: see text] signifies the trace of energy–momentum tensor of a scalar field [Formula: see text]. We follow through the first-order formalism that specifies the scalar field to the Hubble parameter which becomes [Formula: see text] By using Bekenstein–Hawking entropy, we analyze the validity of generalized second law of thermodynamics at apparent horizon for different values of [Formula: see text] and evaluate the equilibrium condition for all cases as well.

scholarly journals Thermodynamics of Various Entropies in Specific Modified Gravity with Particle Creation

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Salman Rafique
Keyword(s):  
Modified Gravity ◽  
Equilibrium Condition ◽  
Apparent Horizon ◽  
Particle Creation ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Fluid Equation ◽  
Generalized Second Law ◽  
Thermal Equilibrium Condition ◽  
Chern Simons

We consider the particle creation scenario in the dynamical Chern-Simons modified gravity in the presence of perfect fluid equation of state p=(γ-1)ρ. By assuming various modified entropies (Bekenstein entropy logarithmic entropy, power law correction, and Renyi entropy), we investigate the first law of thermodynamics and generalized second law of thermodynamics on the apparent horizon. In the presence of particle creation rate, we discuss the generalized second law of thermodynamics and thermal equilibrium condition. It is found that thermodynamics laws and equilibrium condition remain valid under certain conditions of parameters.

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.

Cosmology in scalar–tensor–vector theory via thermodynamics

2018 ◽  
Vol 33 (24) ◽  
pp. 1850137 ◽  
Author(s):  
Onur Siginc ◽  
Mustafa Salti ◽  
Hilmi Yanar ◽  
Oktay Aydogdu
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Entropy Function ◽  
Second Law ◽  
Generalized Second Law ◽  
Vector Theory ◽  
Theory Of Gravity ◽  
The Universe ◽  
Non Equilibrium

Assuming the universe as a thermodynamical system, the second law of thermodynamics can be extended to another form including the sum of matter and horizon entropies, which is called the generalized second law of thermodynamics. The generalized form of the second law (GSL) is universal which means it holds both in non-equilibrium and equilibrium pictures of thermodynamics. Considering the universe is bounded by a dynamical apparent horizon, we investigate the nature of entropy function for the validity of GSL in the scalar–tensor–vector (STEVE) theory of gravity.

scholarly journals Thermodynamic Analysis of Gravitational Field Equations in Lyra Manifold

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
H. Moradpour ◽  
N. Sadeghnezhad ◽  
S. Ghaffari ◽  
A. Jahan
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
De Sitter ◽  
Field Equations ◽  
Frw Universe ◽  
First Law Of Thermodynamics ◽  
Lyra Manifold ◽  
Symmetric Spacetimes ◽  
Horizon Entropy ◽  
Clausius Relation

Considering the Einstein field equations in Lyra manifold and applying the unified first law of thermodynamics as well as the Clausius relation to the apparent horizon of FRW universe, we find the entropy of apparent horizon in Lyra manifold. In addition, the validity of second law of thermodynamics and its generalized form are also studied. Finally, we use the first law of thermodynamics in order to find the horizon entropy of static spherically symmetric spacetimes. Some results of considering (anti)de-Sitter and Schwarzschild metrics have also been addressed.

scholarly journals ENERGY AND ENTROPY OF RELATIVISTIC DIFFUSING PARTICLES

2010 ◽  
Vol 25 (31) ◽  
pp. 2683-2695 ◽  
Author(s):  
Z. HABA
Keyword(s):  
Free Energy ◽  
Time Dependence ◽  
Energy Momentum Tensor ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Second Law ◽  
Entropy Flow ◽  
Fixed Temperature ◽  
Exact Time ◽  
Energy Entropy

We discuss energy–momentum tensor and the second law of thermodynamics for a system of relativistic diffusing particles. We calculate the energy and entropy flow in this system. We obtain an exact time-dependence of energy, entropy and free energy of a beam of photons in a reservoir of a fixed temperature.

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