scholarly journals ENTROPY OF COSMOLOGICAL BLACK HOLES AND THE GENERALIZED SECOND LAW IN THE PHANTOM-ENERGY-DOMINATED UNIVERSE

2011 ◽  
Vol 20 (02) ◽  
pp. 233-252 ◽  
Author(s):  
KHIREDDINE NOUICER
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equation Of State ◽  
State Parameter ◽  
Phantom Energy ◽  
Energy Conditions ◽  
Second Law ◽  
Brick Wall ◽  
Generalized Second Law ◽  
Equation Of State Parameter

Adopting the thin layer improved brick wall method, we investigate the thermodynamics of a black hole embedded in a spatially flat Friedmann–Robertson–Walker universe. We calculate the temperature and the entropy at every apparent horizon for arbitrary solution of the scale factor. We show that the temperature and entropy display a nontrivial behavior as functions of time. In the case of black holes immersed in a universe driven by phantom energy, we show that for specific ranges of the equation-of-state parameter and apparent horizons the entropy is compatible with the D-bound conjecture, and even the null, dominant and strong energy conditions are violated. In the case of accretion of phantom energy onto a black hole with small Hawking–Hayward quasi-local mass, we obtain an equation-of-state parameter in the range w ≤ -5/3, guaranteeing the validity of the generalized second law.

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.

Thermodynamics in loop quantum cosmology with non-canonical scalar field model

2019 ◽  
Vol 16 (06) ◽  
pp. 1950081
Author(s):  
Ayesha Iqbal ◽  
Abdul Jawad
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
Equilibrium Condition ◽  
Field Model ◽  
State Parameter ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Generalized Second Law ◽  
Equation Of State Parameter ◽  
The Universe

The cosmological scenario is built up within the framework of scalar field model possessing a noncanonical kinetic term in loop quantum gravity. The noncanonical scalar field is permitted to interact with dark matter field by assuming a specific form of coupling term. The equation of state parameter is set to be constant as well as variable (Chevallier–Polarski–Linder parametrization) and evaluated the behavior of universe through deceleration parameter and weak energy condition. These parameters favor the accelerated expansion of the universe for three values of equation of state parameter in both cases allowed by observational data. The squared speed of sound leads to the stability of the underlying models in both forms of equation of state parameter. Moreover, the validity of generalized second law of thermodynamics is analyzed by using first law of thermodynamics and assume the universe to be enclosed by apparent horizon. The Bekenstein, logarithmic and power-law entropy is being considered as entropy of horizon. The thermodynamic equilibrium condition is also discussed for all three cases of entropies. The generalized second law of thermodynamics and thermal equilibrium condition is satisfied for all the three types of entropies.

scholarly journals THERMODYNAMICS OF A SCHWARZSCHILD BLACK HOLE IN PHANTOM COSMOLOGY WITH ENTROPY CORRECTIONS

2012 ◽  
Vol 21 (07) ◽  
pp. 1250065 ◽  
Author(s):  
MUBASHER JAMIL ◽  
D. MOMENI ◽  
KAZUHARU BAMBA ◽  
RATBAY MYRZAKULOV
Keyword(s):  
Black Hole ◽  
Power Law ◽  
Phantom Energy ◽  
Upper Bounds ◽  
Quantum Corrections ◽  
Second Law ◽  
Schwarzschild Black Hole ◽  
Frw Universe ◽  
Generalized Second Law ◽  
Entropy Corrections

Motivated by some earlier works [G. Izquierdo and D. Pavon, Phys. Lett. B 639 (2006) 1; H. M. Sadjadi, Phys. Lett. B 645 (2007) 108.] dealing with the study of generalized second law (GSL) of thermodynamics for a system comprising of a Schwarzschild black hole accreting a test nonself-gravitating fluid namely phantom energy in FRW universe, we extend them when the entropy of horizons of black hole and the cosmological undergo quantum corrections. Two types of such corrections are relevant here including logarithmic and power-law, while both are motivated from different theoretical backgrounds. We obtain general mathematical conditions for the validity of GSL in each case. Further we find that GSL restricts the mass of black hole for accretion of phantom energy. As such we obtain upper bounds on the mass of black hole above which the black hole cannot accrete the phantom fluid, otherwise the GSL is violated.

DARK ENERGY WITH POLYTROPIC EQUATION-OF-STATE

2008 ◽  
Vol 23 (37) ◽  
pp. 3187-3198 ◽  
Author(s):  
UTPAL MUKHOPADHYAY ◽  
SAIBAL RAY ◽  
S. B. DUTTA CHOUDHURY
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Closed Form ◽  
State Parameter ◽  
Phantom Energy ◽  
Polytropic Index ◽  
Closed Form Solutions ◽  
Real Nature ◽  
Equation Of State Parameter ◽  
Polytropic Equation

Equation-of-state parameter plays a significant role for guessing the real nature of dark energy. Here polytropic equation-of-state p = ωρnis chosen for some of the kinematical Λ-models viz., [Formula: see text], [Formula: see text] and Λ ~ ρ. Although in dust cases (ω = 0) closed form solutions show no dependency on the polytropic index n, but in non-dust situations some new possibilities are opened up including phantom energy with supernegative (ω < -1) equation-of-state parameter.

scholarly journals The atmosphere of a black hole

2016 ◽  
Vol 31 (05) ◽  
pp. 1650034
Author(s):  
Metin Arik ◽  
Yorgo Senikoglu
Keyword(s):  
Black Hole ◽  
Equation Of State ◽  
State Parameter ◽  
Fluid Solution ◽  
Field Equations ◽  
Equation Of State Parameter ◽  
Special Case ◽  
Isotropic Fluid

We present a static, isotropic fluid solution around a black hole and its effects on the field equations and the horizon. We offer the solutions, their descriptions and we comment on their shortcomings. We derive from the proposed metric the density, the pressure, the equation of state, the temperature near and far of the black hole and the equation of state parameter. We show that for a special case, when [Formula: see text] the solution behaves as [Formula: see text], the equation of state for radiation and for [Formula: see text] we observe that [Formula: see text], the equation of state for dust.

Aspects of nonflat FRW bouncing models with quadratic equation of state

2018 ◽  
Vol 33 (35) ◽  
pp. 1850213 ◽  
Author(s):  
Ashutosh Singh ◽  
Rakesh Raushan ◽  
R. Chaubey ◽  
T. Singh
Keyword(s):  
General Relativity ◽  
Equation Of State ◽  
Bulk Viscosity ◽  
Second Law Of Thermodynamics ◽  
Quadratic Equation ◽  
Energy Conditions ◽  
Second Law ◽  
Generalized Second Law ◽  
Quadratic Equation Of State

In this paper, we investigate the possibility of a nonsingular model of universe in the framework of general relativity in nonflat FRW geometries with quadratic equation of state and bulk viscosity. We study whether a nonsingular bounce requires violation of energy conditions. We discuss the thermodynamical aspects of the resulting models with equilibrium description. In particular, we discuss the validity of the generalized second law of thermodynamics for resulting cosmologies.

scholarly journals Non violation of energy conditions in wormholes modeling

2019 ◽  
Vol 34 (28) ◽  
pp. 1950226 ◽  
Author(s):  
Nisha Godani ◽  
Gauranga C. Samanta
Keyword(s):  
Equation Of State ◽  
Shape Function ◽  
State Parameter ◽  
Energy Conditions ◽  
Shape Functions ◽  
Anisotropic Parameter ◽  
Geometrical Properties ◽  
Traversable Wormholes ◽  
Equation Of State Parameter ◽  
Different Types

Morris and Thorne [M. S. Morris and K. S. Thorne, Am. J. Phys. 56, 395 (1988)] proposed geometrical objects called traversable wormholes that act as bridges in connecting two spacetimes or two different points of the same spacetime. The geometrical properties of these wormholes depend upon the choice of the shape function. In the literature, these are studied in modified gravities for different types of shape functions. In this paper, the traversable wormholes having shape function [Formula: see text] are explored in [Formula: see text] gravity with [Formula: see text], where [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] are real constants. For different values of constants in function [Formula: see text], the analysis is done in various cases. In each case, the energy conditions, equation of state parameter and anisotropic parameter are determined.

scholarly journals ALL "STATIC" SPHERICALLY SYMMETRIC PERFECT FLUID SOLUTIONS OF EINSTEIN'S EQUATIONS WITH CONSTANT EQUATION OF STATE PARAMETER AND FINITE POLYNOMIAL "MASS FUNCTION"

2011 ◽  
Vol 23 (08) ◽  
pp. 865-882 ◽  
Author(s):  
İBRAHİM SEMİZ
Keyword(s):  
Black Hole ◽  
Equation Of State ◽  
Perfect Fluid ◽  
State Parameter ◽  
Phantom Energy ◽  
Mass Function ◽  
Spherically Symmetric ◽  
Einstein’S Equations ◽  
Standard Case ◽  
Einstein's Equations

We look for "static" spherically symmetric solutions of Einstein's Equations for perfect fluid source with equation of state p = wρ, for constant w. We consider all four cases compatible with the standard ansatz for the line element, discussed in previous work. For each case, we derive the equation obeyed by the mass function or its analogs. For these equations, we find all finite-polynomial solutions, including possible negative powers. For the standard case, we find no significantly new solutions, but show that one solution is a static phantom solution, another a black hole-like solution. For the dynamic and/or tachyonic cases we find, among others, dynamic and static tachyonic solutions, a Kantowski–Sachs (KS) class phantom solution, another KS-class solution for dark energy, and a second black hole-like solution. The black hole-like solutions feature segregated normal and tachyonic matter, consistent with the assertion of previous work. In the first black hole-like solution, tachyonic matter is inside the horizon, in the second, outside. The static phantom solution, a limit of an old one, is surprising at first, since phantom energy is usually associated with super-exponential expansion. The KS-phantom solution stands out since its "mass function" is a ninth order polynomial.

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