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 Generalized Misner–Sharp energy in generalized Rastall theory

2020 ◽  
Vol 98 (9) ◽  
pp. 853-856
Author(s):  
H. Moradpour ◽  
M. Valipour
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Spherically Symmetric ◽  
Coupling Coefficients ◽  
Field Equations ◽  
Frw Universe ◽  
Einstein Theory ◽  
First Law Of Thermodynamics ◽  
Horizon Entropy ◽  
Friedmann Robertson Walker

Employing the unified first law of thermodynamics and the field equations of the generalized Rastall theory, we get the generalized Misner–Sharp mass of space–times for which gtt = –grr = –f(r). The obtained result differs from those of the Einstein and Rastall theories. Moreover, using the first law of thermodynamics, the obtained generalized Misner–Sharp mass, and the field equations, the entropy of static spherically symmetric horizons are also addressed in the framework of the generalized Rastall theory. In addition, by generalizing the study to a flat Friedmann–Robertson–Walker (FRW) universe, the apparent horizon entropy is also calculated. Considering the effects of applying the Newtonian limit to the field equations on the coupling coefficients of the generalized Rastall theory, our study indicates (i) the obtained entropy–area relation is the same as that of the Rastall theory, and (ii) the Bekenstein entropy is recovered when the generalized Rastall theory reduces to the Einstein theory. The validity of the second law of thermodynamics is also investigated in the flat FRW universe.

scholarly journals Thermodynamical Study of FRW Universe in Quasi-Topological Theory

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
H. Moradpour ◽  
R. Dehghani
Keyword(s):  
Energy Exchange ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Frw Universe ◽  
Topological Theory ◽  
First Law Of Thermodynamics ◽  
Horizon Entropy ◽  
Topological Gravity ◽  
Entropy Relation

By applying the unified first law of thermodynamics on the apparent horizon of FRW universe, we get the entropy relation for the apparent horizon in quasi-topological gravity theory. Throughout the paper, the results of considering the Hayward-Kodama and Cai-Kim temperatures are also addressed. Our study shows that whenever there is no energy exchange between the various parts of cosmos, we can get an expression for the apparent horizon entropy in quasi-topological gravity, which is in agreement with other attempts that followed different approaches. The effects of a mutual interaction between the various parts of cosmos on the apparent horizon entropy as well as the validity of second law of thermodynamics in quasi-topological gravity are perused.

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 Thermodynamics in f(T) Gravity with Nonminimal Coupling to Matter

2017 ◽  
Vol 2017 ◽  
pp. 1-7
Author(s):  
Tahereh Azizi ◽  
Najibeh Borhani
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Nonminimal Coupling ◽  
Field Equations ◽  
First Law Of Thermodynamics ◽  
Torsion Scalar ◽  
Arbitrary Coupling ◽  
Friedmann Robertson Walker

In the present paper, we study the thermodynamics behavior of the field equations for the generalized f(T) gravity with arbitrary coupling between matter and the torsion scalar. In this regard, we explore the verification of the first law of thermodynamics at the apparent horizon of the Friedmann-Robertson-Walker universe in two different perspectives, namely, the nonequilibrium and equilibrium descriptions of thermodynamics. Furthermore, we investigate the validity of the second law of thermodynamics for both descriptions of this scenario with the assumption that the temperature of matter inside the horizon is similar to that of horizon.

scholarly journals Thermodynamic Analysis of the Static Spherically Symmetric Field Equations in Rastall Theory

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Hooman Moradpour ◽  
Ines G. Salako
Keyword(s):  
Event Horizon ◽  
Thermodynamic Quantities ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Mass Content ◽  
Field Equations ◽  
First Law Of Thermodynamics ◽  
Horizon Entropy ◽  
The One

The restrictions on the Rastall theory due to application of the Newtonian limit to the theory are derived. In addition, we use the zero-zero component of the Rastall field equations as well as the unified first law of thermodynamics to find the Misner-Sharp mass content confined to the event horizon of the spherically symmetric static spacetimes in the Rastall framework. The obtained relation is calculated for the Schwarzschild and de-Sitter back holes as two examples. Bearing the obtained relation for the Misner-Sharp mass in mind together with recasting the one-one component of the Rastall field equations into the form of the first law of thermodynamics, we obtain expressions for the horizon entropy and the work term. Finally, we also compare the thermodynamic quantities of system, including energy, entropy, and work, with their counterparts in the Einstein framework to have a better view about the role of the Rastall hypothesis on the thermodynamics of system.

scholarly journals GENERALIZED SECOND LAW OF THERMODYNAMICS IN WARPED DGP BRANEWORLD

2010 ◽  
Vol 25 (14) ◽  
pp. 1199-1210 ◽  
Author(s):  
AHMAD SHEYKHI ◽  
BIN WANG
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Matter Field ◽  
Second Law ◽  
Intrinsic Curvature ◽  
First Law Of Thermodynamics ◽  
Generalized Second Law ◽  
Curvature Term ◽  
Horizon Entropy ◽  
Dgp Braneworld

We investigate the validity of the generalized second law of thermodynamics on the (n - 1)-dimensional brane embedded in the (n + 1)-dimensional bulk. We examine the evolution of the apparent horizon entropy extracted through relation between gravitational equation and the first law of thermodynamics together with the matter field entropy inside the apparent horizon. We find that the apparent horizon entropy extracted through connection between gravity and the first law of thermodynamics satisfies the generalized second law of thermodynamics. This result holds regardless of whether there is the intrinsic curvature term on the brane or a cosmological constant in the bulk. The observed satisfaction of the generalized second law provides further support on the thermodynamical interpretation of gravity based on the profound connection between gravity and thermodynamics.

scholarly journals Thermodynamics of universe with a varying dark energy component

2015 ◽  
Vol 24 (14) ◽  
pp. 1550098 ◽  
Author(s):  
H. Ebadi ◽  
H. Moradpour
Keyword(s):  
Dark Energy ◽  
Apparent Horizon ◽  
Additional Term ◽  
Second Law Of Thermodynamics ◽  
Mutual Interaction ◽  
Frw Universe ◽  
Energy Component ◽  
Horizon Entropy ◽  
Dark Energy Component ◽  
Friedmann Robertson Walker

We consider a Friedmann–Robertson–Walker (FRW) universe filled by a dark energy (DE) candidate together with other possible sources which may include the baryonic and nonbaryonic matters. Thereinafter, we consider a situation in which the cosmos sectors do not interact with each other. By applying the unified first law of thermodynamics on the apparent horizon of the FRW universe, we show that the DE candidate may modify the apparent horizon entropy and thus the Bekenstein limit. Moreover, we generalize our study to the models in which the cosmos sectors have a mutual interaction. Our final result indicates that the mutual interaction between the cosmos sectors may add an additional term to the apparent horizon entropy leading to modify the Bekenstein limit. Relationships with previous works have been addressed throughout the paper. Finally, we investigate the validity of the second law of thermodynamics and its generalized form in the interacting and noninteracting cosmoses.

Modified cosmology through Renyi and logarithmic entropies

2018 ◽  
Vol 15 (08) ◽  
pp. 1850130 ◽  
Author(s):  
Abdul Jawad ◽  
Ayesha Iqbal
Keyword(s):  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Renyi Entropy ◽  
Rényi Entropy ◽  
Entropic Force ◽  
Frw Universe ◽  
First Law Of Thermodynamics ◽  
Corrected Entropy ◽  
Generalized Second Law ◽  
Entropy Corrections

We consider two different entropic corrections to Bekenstein entropy, namely Renyi entropy and logarithmic-corrected entropy, and develop the entropic force, heat flow across the horizon and pressure. We also derive the expressions for Newton’s law of gravitation and verify with Bekenstein entropy by taking [Formula: see text] in the case of Renyi entropy and [Formula: see text] for logarithmic entropy. The modified Friedmann equations are also being developed by using Newton’s first law of thermodynamics in both cases. In the presence of these equations, we also analyze the validity of generalized second law of thermodynamics for both entropy corrections on the apparent horizon. It is found that this law remains valid throughout the region under certain assumptions for nonflat FRW universe.

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.

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