scholarly journals Singularities, Black Holes, and Cosmic Censorship: A Tribute to Roger Penrose

2021 ◽  
Vol 51 (2) ◽  
Author(s):  
Klaas Landsman
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmic Censorship ◽  
Early History ◽  
Singularity Theorem ◽  
Null Infinity ◽  
Strong Cosmic Censorship ◽  
History Of ◽  
Definition Of ◽  
Fundamental Tension

AbstractIn the light of his recent (and fully deserved) Nobel Prize, this pedagogical paper draws attention to a fundamental tension that drove Penrose’s work on general relativity. His 1965 singularity theorem (for which he got the prize) does not in fact imply the existence of black holes (even if its assumptions are met). Similarly, his versatile definition of a singular space–time does not match the generally accepted definition of a black hole (derived from his concept of null infinity). To overcome this, Penrose launched his cosmic censorship conjecture(s), whose evolution we discuss. In particular, we review both his own (mature) formulation and its later, inequivalent reformulation in the pde literature. As a compromise, one might say that in “generic” or “physically reasonable” space–times, weak cosmic censorship postulates the appearance and stability of event horizons, whereas strong cosmic censorship asks for the instability and ensuing disappearance of Cauchy horizons. As an encore, an “Appendix” by Erik Curiel reviews the early history of the definition of a black hole.

scholarly journals A proof of the strong cosmic censorship conjecture

2020 ◽  
Vol 29 (14) ◽  
pp. 2042003
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Second Law Of Thermodynamics ◽  
Cosmic Censorship ◽  
Necessary Condition ◽  
Deterministic Theory ◽  
Black Hole Spacetimes ◽  
Generalized Second Law ◽  
Strong Cosmic Censorship ◽  
Cosmic Censorship Conjecture

The Penrose strong cosmic censorship conjecture asserts that Cauchy horizons inside dynamically formed black holes are unstable to remnant matter fields that fall into the black holes. The physical importance of this conjecture stems from the fact that it provides a necessary condition for general relativity to be a truly deterministic theory of gravity. Determining the fate of the Penrose conjecture in nonasymptotically flat black hole spacetimes has been the focus of intense research efforts in recent years. In this paper, we provide a remarkably compact proof, which is based on Bekenstein’s generalized second law of thermodynamics, for the validity of the intriguing Penrose conjecture in physically realistic (dynamically formed) curved black hole spacetimes.

scholarly journals Black-hole boundaries

2005 ◽  
Vol 83 (11) ◽  
pp. 1073-1099 ◽  
Author(s):  
Ivan Booth
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Recent Work ◽  
Numerical Relativity ◽  
Null Infinity ◽  
Event Horizons ◽  
Traditional Definition ◽  
Classical Black Holes ◽  
Definition Of ◽  
Future Null Infinity

Classical black holes and event horizons are highly nonlocal objects, defined in relation to the causal past of future null infinity. Alternative, quasilocal characterizations of black holes are often used in mathematical, quantum, and numerical relativity. These include apparent, Killing, trapping, isolated, dynamical, and slowly evolving horizons. All of these are closely associated with two-surfaces of zero outward null expansion. This paper reviews the traditional definition of black holes and provides an overview of some of the more recent work on alternative horizons.PACS Nos.: 04.20.Cv, 04.70.–s, 04.70.Bw

scholarly journals Quasi-normal modes of near-extremal black holes in generalized spherically symmetric spacetime and strong cosmic censorship conjecture

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Piyabut Burikham ◽  
Supakchai Ponglertsakul ◽  
Taum Wuthicharn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Normal Modes ◽  
Cosmic Censorship ◽  
Analytic Formula ◽  
Spherically Symmetric ◽  
Black Hole Background ◽  
Strong Cosmic Censorship ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole

AbstractA number of near-extremal conditions are utilized to simplify the equation of motion of the neutral scalar perturbations in generalized spherically symmetric black hole background into a differential equation with the Pöschl–Teller potential. An analytic formula for quasinormal frequencies is obtained. The analytic formula is then used to investigate strong cosmic censorship conjectures (SCC) of the generalized black hole spacetime for the smooth initial data. The Christodoulou version of the SCC is found to be violated for certain regions of the black hole parameter space including the black holes in general relativity while the $$C^{1}$$ C 1 version of the SCC is always valid.

MM IA Pottery from Evans' Excavations at Knossos: A Reassessment

1991 ◽  
Vol 86 ◽  
pp. 149-271 ◽  
Author(s):  
Nicoletta Momigliano
Keyword(s):  
Ceramic Material ◽  
Early History ◽  
History Of ◽  
Ceramic Assemblages ◽  
Definition Of ◽  
Written Sources

This article is a critical reassessment of the major Knossian deposits assigned by Evans to the Middle Minoan I A phase. It is divided into three main sections: first, an introduction, in which the author discusses the development of the definition of Knossian MM IA pottery; second, a detailed discussion of each deposit, based upon a systematic and first-hand re-examination of the ceramic material, and of the relevant written sources; third, a discussion of the problems concerning the classification of these deposits, and a typological study of their ceramic assemblages. The picture of Knossian MM IA pottery which emerges from this study is remarkably different from that presented by Evans, which is generally accepted. This has further implications not only for the study of Minoan pottery, but also for the early history of the site.

The effect of dark matter on the weak cosmic censorship conjecture in the extended space

2021 ◽  
pp. 2150207
Author(s):  
Zi-Yu Fu ◽  
Bao-Qi Zhang ◽  
Chuan-Yin Wang ◽  
Hui-Ling Li
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Second Law Of Thermodynamics ◽  
Cosmic Censorship ◽  
De Sitter ◽  
Extended Phase ◽  
Extended Space ◽  
Extreme Black Holes ◽  
Cosmic Censorship Conjecture

By analyzing the energy–momentum relationship of the absorbed fermions dropping into a Reissner–Nordstöm–anti-de Sitter black hole surrounded by dark matter, the laws of thermodynamic and weak cosmic censorship conjecture in the extended phase space are investigated. We find that the first law of thermodynamics is valid. However, the validity of the second law of thermodynamics depends on the density [Formula: see text] of the perfect fluid dark matter. In addition, we also find that when the fermions are absorbed, the structures of black hole surrounded by dark matter would not change. Therefore, weak cosmic censorship conjecture holds for the extreme black holes and the non-extreme black holes.

Dynamical black holes

2020 ◽  
pp. 312-336
Author(s):  
Piotr T. Chruściel
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cauchy Data ◽  
Einstein Equations ◽  
Black Hole Spacetimes ◽  
Alternative Approaches ◽  
Definition Of ◽  
Meaningful Definition ◽  
Stability Results ◽  
Black Hole Solutions

In this chapter we review what is known about dynamical black hole-solutions of Einstein equations. We discuss the Robinson–Trautman black holes, with or without a cosmological constant. We review the Cauchy-data approach to the construction of black-hole spacetimes. We propose some alternative approaches to a meaningful definition of black hole in a dynamical spacetime, and we review the nonlinear stability results for black-hole solutions of vacuum Einstein equations.

scholarly journals New version of the gedanken experiments to test the weak cosmic censorship in charged dilaton-Lifshitz black holes

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Jie Jiang ◽  
Ming Zhang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Order Approximation ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Cosmic Censorship ◽  
Second Order ◽  
Lifshitz Black Holes ◽  
Lifshitz Black Hole ◽  
Matter Fields

AbstractIn this paper, based on the new version of the gedanken experiments proposed by Sorce and Wald, we examine the weak cosmic censorship in the perturbation process of accreting matter fields for the charged dilaton-Lifshitz black holes. In the investigation, we assume that the black hole is perturbed by some extra matter source satisfied the null energy condition and ultimately settle down to a static charged dilaton-Lifshitz black hole in the asymptotic future. Then, after applying the Noether charge method, we derive the first-order and second-order perturbation inequalities of the perturbation matter fields. As a result, we find that the nearly extremal charged dilaton-Lifshitz black hole cannot be destroyed under the second-order approximation of perturbation. This result implies that the weak cosmic censorship conjecture might be a general feature of the Einstein gravity, and it is independent of the asymptotic behaviors of the black holes.

scholarly journals Strong cosmic censorship under quasinormal modes of non-minimally coupled massive scalar field

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Bogeun Gwak
Keyword(s):  
Black Holes ◽  
Scalar Field ◽  
Decay Rate ◽  
Small Mass ◽  
Cosmic Censorship ◽  
Massive Scalar ◽  
De Sitter ◽  
Massive Scalar Field ◽  
Strong Cosmic Censorship ◽  
Cosmic Censorship Conjecture

Abstract We investigate the strong cosmic censorship conjecture in lukewarm Reissner–Nordström–de Sitter black holes (and Martínez–Troncoso–Zanelli black holes) using the quasinormal resonance of non-minimally coupled massive scalar field. The strong cosmic censorship conjecture is closely related to the stability of the Cauchy horizon governed by the decay rate of the dominant quasinormal mode. Here, dominant modes are obtained in the limits of small and large mass black holes. Then, we connect the modes by using the WKB approximation. In our analysis, the strong cosmic censorship conjecture is valid except in the range of the small-mass limit, in which the dominant mode can be assumed to be that of the de Sitter spacetime. Particularly, the coupling constant and mass of the scalar field determine the decay rate in the small mass range. Therefore, the validity of the strong cosmic censorship conjecture depends on the characteristics of the scalar field.

The entropy evolution of a Schwarzschild–(Anti) de Sitter black hole

2020 ◽  
Vol 29 (07) ◽  
pp. 2050048
Author(s):  
Xin-Yang Wang ◽  
Yi-Ru Wang ◽  
Wen-Biao Liu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Hawking Radiation ◽  
Dynamical Variable ◽  
De Sitter ◽  
The One ◽  
Definition Of ◽  
Spherically Symmetry ◽  
Interior Volume

Based on the definition of the interior volume of spherically symmetry black holes, the interior volume of Schwarzschild–(Anti) de Sitter black holes is calculated. It is shown that with the cosmological constant ([Formula: see text]) increasing, the changing behaviors of both the position of the largest hypersurface and the interior volume for the Schwarzschild–Anti de Sitter black hole are the same as the Schwarzschild–de Sitter black hole. Considering a scalar field in the interior volume and Hawking radiation with only energy, the evolution relation between the scalar field entropy and Bekenstein–Hawking entropy is constructed. The results show that the scalar field entropy is approximately proportional to Bekenstein–Hawking entropy during Hawking radiation. Meanwhile, the proportionality coefficient is also regarded as a constant approximately with the increasing [Formula: see text]. Furthermore, considering [Formula: see text] as a dynamical variable, the modified Stefan–Boltzmann law is proposed which can be used to describe the variation of both the mass and [Formula: see text] under Hawking radiation. Using this modified law, the evolution relation between the two types of entropy is also constructed. The results show that the coefficient for Schwarzschild–de Sitter black holes is closer to a constant than the one for Schwarzschild–Anti de Sitter black holes during the evaporation process. Moreover, we find that for Hawking radiation carrying only energy, the evolution relation is a special case compared with the situation that the mass and [Formula: see text] are both considered as dynamical variables.

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