Thermodynamical aspects of nonsingular Brans–Dicke cosmologies

2020 ◽  
Vol 35 (10) ◽  
pp. 2050054 ◽  
Author(s):  
Ashutosh Singh ◽  
A. K. Shukla
Keyword(s):  
Time Evolution ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Jordan Frame ◽  
Total Entropy ◽  
Generalized Second Law ◽  
Contracting Phase

The time evolution of total entropy including the entropy associated with horizon and entropy of matter inside the horizon in homogeneous and isotropic Jordan frame (dilatonic) Brans–Dicke cosmologies is examined. We show that the bouncing Brans–Dicke cosmologies do not satisfy the generalized second law of thermodynamics during the contracting phase of evolution.

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.

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 in chameleon cosmology

2011 ◽  
Vol 89 (9) ◽  
pp. 915-919 ◽  
Author(s):  
H. Farajollahi ◽  
A. Salehi ◽  
F. Tayebi
Keyword(s):  
Equation Of State ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Total Entropy ◽  
Generalized Second Law ◽  
Phantom Crossing ◽  
Hubble Parameters ◽  
The Universe

In this paper, we investigate the validity of the generalized second law of thermodynamics in flat Friedmann–Lemaître–Robertson–Walker chameleon cosmology where the boundary of the universe is assumed to be enclosed by the dynamical apparent horizon. It has been shown that, in a bouncing scenario for the universe with phantom crossing, the total entropy decreases with time in the contracting epoch, whereas, the dynamics of the internal and horizon entropies depend on the behaviour of both the equation of state and the Hubble parameters.

Cosmological consequences of modified Friedmann equations according to holographic equipartition law

2021 ◽  
Vol 36 (10) ◽  
pp. 2150069
Author(s):  
Abdul Jawad ◽  
Sidra Saleem ◽  
Saba Qummer
Keyword(s):  
Equation Of State ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Om Diagnostic ◽  
Generalized Second Law ◽  
Friedmann Equations ◽  
Equation Of State Parameter ◽  
Equipartition Law

We examine thermodynamically an extra driving term for the flat universe by applying Sharma Mittal entropy to Padmanabhan’s holographic equipartition law. Deviations from the Bekenstein–Hawking entropy by using this law, we generate an extra driving in the acceleration equation. By using the constant and parametrized equation of state parameter, we investigate the different cosmological parameters like deceleration parameter, squared speed of sound, Om-diagnostic and statefinder parameter through graphical approach. We observe compatible results with current observational data in both models. Generalized second law of thermodynamics also remains valid in both cases.

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 The generalized second law of thermodynamics in the accelerating universe

2007 ◽  
Vol 652 (2-3) ◽  
pp. 86-91 ◽  
Author(s):  
Jia Zhou ◽  
Bin Wang ◽  
Yungui Gong ◽  
Elcio Abdalla
Keyword(s):  
Second Law Of Thermodynamics ◽  
Accelerating Universe ◽  
Second Law ◽  
Generalized Second Law
Sign in / Sign up

Export Citation Format

Share Document