Generalized second law of thermodynamics in black-hole physics

1974 ◽  
Vol 9 (12) ◽  
pp. 3292-3300 ◽  
Author(s):  
Jacob D. Bekenstein
Keyword(s):  
Black Hole ◽  
Black Hole Physics ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Generalized Second Law

scholarly journals Generalized second law and universal relations of cosmological black hole

2019 ◽  
Vol 9 (2) ◽  
pp. 281-288
Author(s):  
Ashfaque H. Bokhari ◽  
M. Akbar ◽  
Tayeb Brahimi
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Cosmological Horizon ◽  
Generalized Second Law ◽  
Area Product ◽  
Mass Dependent ◽  
Product Relation

Abstract The objective of this paper is to investigate the validity conditions for the generalized second law of thermodynamics, and the universal relations for multi-horizon dynamical spacetime. It is found that there are three horizons of McVittie universe termed as event horizon, cosmological apparent horizon, and virtual horizon. The mass-dependent and mass-independent area product relations are formulated in terms of areas of the dynamical event horizon, cosmological horizon and virtual horizon. It is noted that whereas the area sum relation is mass independent, the area product relation is explicitly mass dependent. Moreover, we have also analyzed and listed explicit mass-independent and mass-dependent relations.

scholarly journals The generalized second law of thermodynamics with Barrow entropy

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Emmanuel N. Saridakis ◽  
Spyros Basilakos
Keyword(s):  
Black Hole ◽  
Dark Energy ◽  
Apparent Horizon ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Gravitational Effects ◽  
Generalized Second Law ◽  
Horizon Entropy ◽  
The Universe ◽  
Universe Evolution

AbstractWe investigate the validity of the generalized second law of thermodynamics, applying Barrow entropy for the horizon entropy. The former arises from the fact that the black-hole surface may be deformed due to quantum-gravitational effects, quantified by a new exponent $$\Delta $$ Δ . We calculate the entropy time-variation in a universe filled with the matter and dark energy fluids, as well as the corresponding quantity for the apparent horizon. We show that although in the case $$\Delta =0$$ Δ = 0 , which corresponds to usual entropy, the sum of the entropy enclosed by the apparent horizon plus the entropy of the horizon itself is always a non-decreasing function of time and thus the generalized second law of thermodynamics is valid, in the case of Barrow entropy this is not true anymore, and the generalized second law of thermodynamics may be violated, depending on the universe evolution. Hence, in order not to have violation, the deformation from standard Bekenstein–Hawking expression should be small as expected.

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.

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