Quasi-black holes: Definition and general properties

Lemos, José P. S.; Заславский, О. Б.

doi:10.1103/physrevd.76.084030

Cited by 62 publications

(142 citation statements)

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“…Such a kind of behavior is called naked behavior, and many instances of it have been found [9,10,11,12,13,14,15,16]. Another example is with quasi-black holes [5]. One of the features typical of quasi-black holes, consists in precisely showing naked behavior on and beyond the quasihorizon surface.…”

Section: Equations and Setup For Mimickersmentioning

confidence: 99%

“…Within the uncharged or charged but non-extremal one can invoke as black hole mimickers, non-extremal ε-wormholes on the threshold of the formation of an event horizon, some of which are called black foils [2] (see [3] for the construction with other purposes of ε-wormholes, which actually can also act as mimickers), and gravastars [4]. Within the extremal charged class one can invoke extremal ε-wormholes on the threshold of the formation of an event horizon, quasi-black holes [5] (see also [6]), and wormholes on the basis of quasi-black holes from Bonnor stars, to name a few. We want to elucidate, whether or not the objects belonging to these two classes remain regular in the near-horizon limit.…”

Section: Introductionmentioning

confidence: 99%

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Black hole mimickers: Regular versus singular behavior

Lemos¹,

Заславский

2008

Phys. Rev. D

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Black hole mimickers are possible alternatives to black holes, they would look observationally almost like black holes but would have no horizon. The properties in the near-horizon region where gravity is strong can be quite different for both type of objects, but at infinity it could be difficult to discern black holes from their mimickers.To disentangle this possible confusion, we examine the near-horizon properties, and their connection with far away asymptotic properties, of some candidates to black mimickers. We study spherically symmetric uncharged or charged but non-extremal objects, as well as spherically symmetric charged extremal objects. Within the uncharged or charged but non-extremal black hole mimickers, we study non-extremal ε-wormholes on the threshold of the formation of an event horizon, of which a subclass are called black foils, and gravastars. Within the charged extremal black hole mimickers we study extremal ε-wormholes on the threshold of the formation of an event horizon, quasi-black holes, and wormholes on the basis of quasi-black holes from Bonnor stars. We elucidate, whether or not the objects belonging to these two classes remain regular in the near-horizon limit. The requirement of full regularity, i.e., finite curvature and absence of naked behavior, up to an arbitrary neighborhood of the gravitational radius of the object enables one to rule out potential mimickers in most of the cases. A list ranking the best black hole mimickers up to the worse, both non-extremal and extremal, is as follows: wormholes on the basis of extremal black holes or on the basis of quasi-black holes, quasi-black holes, wormholes on the 2 basis of non-extremal black holes (black foils), and gravastars. Since, in observational astrophysics it is difficult to find extremal configurations (the best mimickers in the ranking), whereas non-extremal configurations are really bad mimickers, the task of distinguishing black holes from their mimickers seems to be less difficult than one could think of it.

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Section: Equations and Setup For Mimickersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Black hole mimickers: Regular versus singular behavior

Lemos¹,

Заславский

2008

Phys. Rev. D

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“…Although to external observers the system looks like an extremal black hole, its internal properties are very different from what one could expect in the case of a standard black hole. These properties, along similar ones of gravitational magnetic monopoles and glued vacuum solutions with shells, have been analyzed in [16,17]. In [18] other attributes of these systems were explored.…”

Section: Bonnor Stars: Junction Of Dust With Vacuum Majumdar-papapetrmentioning

confidence: 99%

“…Later, it was shown that the hoop should be reduced for extremal charged matter to ∼ 2πGM [9,10]. However, it seems that systems like Bonnor stars violate it, since no black hole forms ever, only a quasi-black hole [16,17]. (v) A pertinent question, specially related to stars, is whether they can form from gravitational collapse or not.…”

Section: Further Connectionsmentioning

confidence: 99%

“…Moreover, in the limit ε → 0 the interior metric potential B i obeys, B i → 0, for all r/µ ≤ 1. These three features define a quasi-black hole, see [16,17]. These three features imply, among other things, that (a) there are infinite redshift whole regions rather than surfaces, (b) the object displays naked behavior, i.e., generation of infinite tidal forces in a freely falling frame, (c) outer and inner regions become impenetrable and disjoint, and (d) for external distant observers the spacetime is indistinguishable from that of extremal black holes.…”

Section: (I) Solutions With Smooth Boundary Conditions and Some Specimentioning

confidence: 99%

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Bonnor stars indspacetime dimensions

Lemos¹,

Zanchin

2008

Phys. Rev. D

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Bonnor stars are regular static compact configurations in equilibrium, composed of an extremal dust fluid, i.e., a charged dust fluid where the mass density is equal to the charge density in appropriate units and up to a sign, joined to a suitable exterior vacuum solution, both within Newtonian gravity and general relativity.In four dimensions, these configurations obey the Majumdar-Papapetrou system of equations, in one case, the system is a particular setup of Newtonian gravity coupled to Coulomb electricity and electrically charged matter or fluid, in the other case, the system is a particular setup of general relativity coupled to Maxwell electromagnetism and electrically charged matter or fluid, where the corresponding gravitational potential is a specially simple function of the electric potential field and the fluid, when there is one, is made of extremal dust. Since the Majumdar-Papapetrou system can be generalized to d spacetime dimensions, as has been previously done, and higher dimensional scenarios can be important in gravitational physics, it is natural to study this type of Bonnor solutions in higher dimensions, d ≥ 4. As a preparation, we analyze Newton-Coulomb theory with an electrically charged fluid in a Majumdar-Papapetrou context, in d = n + 1 spacetime dimensions, with n being the number of spatial dimensions. We show that within the Newtonian theory, in vacuum, the Majumdar-Papapetrou relation for the gravitational potential in terms of the electric potential, and its related Weyl relation, are equivalent, in contrast with general relativity where they are distinct. We study a class of spherically symmetric Bonnor stars within this theory. Under sufficient compactification they form point mass charged Newtonian singularities. We then study the analogue type systems in the Einstein-Maxwell theory with an electrically charged fluid. Drawing on our previous work on the d-dimensional Majumdar-Papapetrou system, we restate some properties of this system. We obtain spherically symmetric Bonnor star solutions in d = n + 1 spacetime dimensions. We show that these stars, under sufficient compactification, form d-dimensional quasi-black holes. We also show that in the appropriate low gravity limit theses solutions turn into the solutions of Newtonian gravity, i.e., they are quasi-Newtonian Bonnor stars. In this connection, we note that the star solutions in Majumdar-Papapetrou Newtonian gravity, when contrasted to those solutions in Majumdar-Papapetrou general relativity, display clearly the branching off of the high density objects that may arise in the strong field regime of each theory, mild singularities in one theory, quasi-black holes in the other. Another important feature worth of mention is that, whereas there are no solutions for Newtonian or relativistic stars supported by degenerate pressure in higher dimensions, higher dimensional Bonnor stars, supported by electric repulsion, do indeed have solutions within Newtonian gravity and general relativity. So the existence of stars in h...

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Black Holes in Asymptotically Safe Gravity

Platania

2023

Handbook of Quantum Gravity

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Quasi-black holes: Definition and general properties

Cited by 62 publications

References 37 publications

Black hole mimickers: Regular versus singular behavior

Black hole mimickers: Regular versus singular behavior

Bonnor stars indspacetime dimensions

Black Holes in Asymptotically Safe Gravity

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