scholarly journals Cosmic censorship hypothesis and entropy bound on black holes in a canonical ensemble

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Run-Qiu Yang
Keyword(s):  
Black Holes ◽  
Canonical Ensemble ◽  
Cosmic Censorship ◽  
Entropy Bound ◽  
Cosmic Censorship Hypothesis

scholarly journals HIGHER DIMENSIONAL INHOMOGENEOUS DUST COLLAPSE AND COSMIC CENSORSHIP

2002 ◽  
Vol 17 (20) ◽  
pp. 2747-2747
Author(s):  
A. BEESHAM
Keyword(s):  
Black Holes ◽  
Cosmic Censorship ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Naked Singularities ◽  
Singularity Theorems ◽  
Sitter Spacetime ◽  
Higher Dimensional ◽  
Cosmic Censorship Hypothesis ◽  
Strong Curvature

The singularity theorems of general relativity predict that gravitational collapse finally ends up in a spacetime singularity1. The cosmic censorship hypothesis (CCH) states that such a singularity is covered by an event horizon2. Despite much effort, there is no rigorous formulation or proof of the CCH. In view of this, examples that appear to violate the CCH and lead to naked singularities, in which non-spacelike curves can emerge, rather than black holes, are important to shed more light on the issue. We have studied several collapse scenarios which can lead to both situations3. In the case of the Vaidya-de Sitter spacetime4, we have shown that the naked singularities that arise are of the strong curvature type. Both types of singularities can also arise in higher dimensional Vaidya and Tolman-Bondi spacetimes, but black holes are favoured in some sense by the higher dimensions. The charged Vaidya-de Sitter spacetime also exhibits both types of singularities5.

The physics of black holes II

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Energy Condition ◽  
Kerr Black Hole ◽  
Cosmic Censorship ◽  
Quantum Field ◽  
Schwarzschild Solution ◽  
Physics Of Black Holes ◽  
Penrose Process ◽  
Cosmic Censorship Hypothesis

This chapter gives a brief description of Hawking radiation, which involves a combination of general relativity and quantum field theory and leads to a thermodynamical interpretation of the laws governing the evolution of black holes. The study of the Penrose process near a Kerr black hole leads to the conclusion that its irreducible mass can only increase. A similar but more general conclusion was reached by Hawking, who showed that the sum of the areas of the horizons of black holes interacting with matter can only increase, with the condition that the cosmic censorship hypothesis is valid and that the matter obeys the so-called weak energy condition. The chapter concludes with the Israel theorem, which allows one to argue that if gravitation is described by general relativity, then not only do black holes exist, but all black holes are represented by the Kerr–Schwarzschild solution.

scholarly journals Vaidya Collapse with Nonzero Radial Pressure and Charge

Axioms ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 52
Author(s):  
Aroonkumar Beesham
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Initial Conditions ◽  
Radial Pressure ◽  
Cosmic Censorship ◽  
Cosmological Parameter ◽  
Naked Singularities ◽  
Physical Conditions ◽  
Cosmic Censorship Hypothesis ◽  
Nonzero Charge

The cosmic censorship hypothesis is regarded as one of the most important unsolved problems in classical general relativity; viz., will generic gravitational collapse of a star after it has exhausted its nuclear fuel lead to black holes only, under reasonable physical conditions. We discuss the collapse of a fluid with nonzero radial pressure within the context of the Vaidya spacetime considering a decaying cosmological parameter as well as nonzero charge. Previously, a similar analysis was done, but without considering charge. A decaying cosmological parameter may also be associated with dark energy. We found that both black holes and naked singularities can form, depending upon the initial conditions. Hence, charge does not restore the validity of the hypothesis. This provides another example of the violation of the cosmic censorship hypothesis. We also discuss some radiating rotating solutions, arriving at the same conclusion.

Cosmic censorship in overcharging the Reissner–Nordström anti-de-Sitter black hole with Global Monopole charge

2020 ◽  
Vol 35 (17) ◽  
pp. 2050140
Author(s):  
Ayyesha K. Ahmed
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmic Censorship ◽  
Global Monopole ◽  
De Sitter ◽  
Cosmic Censorship Hypothesis

We investigate the cosmic censorship hypothesis for the Reissner–Nordström anti-de-Sitter black holes with global monopole charge. Considering the motion of the particle, we find that the overcharging is possible only for the anti-de-Sitter black hole showing violation of the cosmic censorship hypothesis. However, for the de-Sitter black hole, overcharging is not possible and hence there is no violation of the cosmic censorship hypothesis.

scholarly journals Overcharging black holes and cosmic censorship in Eddington-inspired Born-Infeld gravity

2018 ◽  
Vol 98 (12) ◽  
Author(s):  
Soumya Jana ◽  
Rajibul Shaikh ◽  
Sudipta Sarkar
Keyword(s):  
Black Holes ◽  
Cosmic Censorship

scholarly journals On Boundedness of Entropy of Photon Gas in Noncommutative Spacetime

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Kazi Ashraful Alam ◽  
Mir Mehedi Faruk
Keyword(s):  
Black Holes ◽  
Distribution Function ◽  
Phase Space ◽  
Partition Function ◽  
Boltzmann Distribution ◽  
Einstein Distribution ◽  
Entropy Bound ◽  
Photon Gas ◽  
Noncommutative Spacetime ◽  
Bose Einstein

Entropy bound for the photon gas in a noncommutative (NC) spacetime where phase space is with compact spatial momentum space, previously studied by Nozari et al., has been reexamined with the correct distribution function. While Nozari et al. have employed Maxwell-Boltzmann distribution function to investigate thermodynamic properties of photon gas, we have employed the correct distribution function, that is, Bose-Einstein distribution function. No such entropy bound is observed if Bose-Einstein distribution is employed to solve the partition function. As a result, the reported analogy between thermodynamics of photon gas in such NC spacetime and Bekenstein-Hawking entropy of black holes should be disregarded.

Sign in / Sign up

Export Citation Format

Share Document