scholarly journals Brans–Dicke theory and thermodynamical laws on apparent and event horizons

2011 ◽  
Vol 89 (8) ◽  
pp. 883-889 ◽  
Author(s):  
Samarpita Bhattacharya ◽  
Ujjal Debnath
Keyword(s):  
Scalar Field ◽  
Event Horizon ◽  
Apparent Horizon ◽  
First Law Of Thermodynamics ◽  
Generalized Second Law ◽  
Particular Solution ◽  
Validity Condition ◽  
Theory Of Gravity ◽  
Thermodynamical Laws ◽  
Entropy Relation

In this work, we describe the Brans–Dicke (BD) theory of gravity and give a particular solution by choosing a power law form for the scalar field [Formula: see text] and constant ω. If we assume that the first law of thermodynamics and the entropy formula hold on the apparent horizon, then we recover the Friedmann equations. Next, assuming the first law of thermodynamics holds, the validity conditions of the generalized second law (GSL) on the event horizon are presented. If we impose the entropy relation on the horizon, without using the first law, then we also obtain the validity condition of the GSL on the event horizon. The validity of the GSL completely depends on the BD model scalar field solutions. We have justified that the two processes are equivalent on the apparent horizon, but on the event horizon they are not equivalent. If the first law is valid on the event horizon, then the GSL may be satisfied by the BD solution, but if the first law is not satisfied then the GSL is not satisfied by the BD solution. Therefore, the first law always favours the GSL on the event horizon. In our effective approach, the first law and the GSL are always satisfied on the apparent horizon, which does not depend on the BD theory of gravity.

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.

scholarly journals Gravitational collapse in the AdS background and the black hole formation

2016 ◽  
Vol 25 (01) ◽  
pp. 1650005 ◽  
Author(s):  
Alireza Allahyari ◽  
Javad T. Firouzjaee ◽  
Reza Mansouri
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Event Horizon ◽  
Gravitational Collapse ◽  
Apparent Horizon ◽  
Rapid Change ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Hole Formation ◽  
Thermalization Time

We study the time evolution of the Misner-Sharp mass and the apparent horizon for gravitational collapse of a massless scalar field in the [Formula: see text] spacetime for both cases of narrow and broad waves by numerically solving the Einstein’s equations coupled to a massless scalar field. This is done by relying on the full dynamics of the collapse including the concept of the dynamical horizon. It turns out that the Misner-Sharp mass is everywhere constant except for a rapid change across a thin shell defined by the density profile of the collapsing wave. By studying the evolution of the apparent horizon, indicating the formation of a black hole at different times we see how asymptotically an event horizon forms. The dependence of the thermalization time on the radius of the initial black hole event horizon is also studied.

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.

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 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.

Fluctuation on a Schwarzschild black hole

2009 ◽  
Vol 87 (9) ◽  
pp. 1009-1012 ◽  
Author(s):  
Xianming Liu ◽  
Wenbiao Liu
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Hawking Radiation ◽  
Apparent Horizon ◽  
Gravitational Anomaly ◽  
Schwarzschild Black Hole ◽  
First Law Of Thermodynamics ◽  
Vaidya Black Hole

When a relativistic perturbation is given to the horizon of a Schwarzschild black hole, a new supersurface near the horizon will be obtained. Using the gravitational anomaly method proposed by Robinson and Wilczek, Hawking radiation from this new supersurface is calculated. It is found that the first law of thermodynamics can also be constructed successfully on this supersurface. The expressions of the characteristic position and temperature are very similar to the previous results for the event horizon of a Vaidya black hole. Comparing with the Vaidya black hole, we conclude that Hawking radiation and the thermodynamics of a Vaidya black hole should be indeed constructed at the apparent horizon instead of the event horizon.

TORTOISE COORDINATE TRANSFORMATION ON APPARENT HORIZON OF A DYNAMICAL BLACK HOLE

2012 ◽  
Vol 12 ◽  
pp. 358-367 ◽  
Author(s):  
XIANMING LIU ◽  
ZHENG ZHAO ◽  
WENBIAO LIU
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Hawking Radiation ◽  
Coordinate Transformation ◽  
Apparent Horizon ◽  
Schwarzschild Black Hole ◽  
First Law Of Thermodynamics ◽  
Vaidya Black Hole ◽  
Tortoise Coordinate ◽  
Tortoise Coordinate Transformation

Thinking of Hawking radiation calculation from a Schwarzschild black hole using Damour-Ruffini method, some key requirements of the tortoise coordinate transformation are pointed out. Extending these requirements to a dynamical black hole, a dynamical tortoise coordinate transformation is proposed. Under this new dynamical tortoise coordinate transformation, Hawking radiation from a Vaidya black hole can be got successfully using Damour-Ruffini method. Moreover, we also find that the radiation should be regarded as originating from the apparent horizon rather than the event horizon at least from the viewpoint of the first law of thermodynamics.

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.

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.

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