Black-bounce to traversable wormhole

Simpson, Alex; Visser, Matt

doi:10.1088/1475-7516/2019/02/042

Cited by 261 publications

(327 citation statements)

References 98 publications

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“…Let us mention that this kind of geometric structure has been described in situations in which it leads to a bounce into another universe (see [26,27] and [28,29]). However, the spacetimes discussed in these papers are not globally hyperbolic, but display partial Cauchy surfaces [8] with topology R × S 2 .…”

Section: Arxiv:190803261v1 [Gr-qc] 8 Aug 2019mentioning

confidence: 99%

Opening the Pandora’s box at the core of black holes

Carballo-Rubio

Filippo

Liberati

et al. 2020

Class. Quantum Grav.

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Unless the reality of spacetime singularities is assumed, astrophysical black holes cannot be identical to their mathematical counterparts obtained as solutions of the Einstein field equations. Mechanisms for singularity regularization would spark deviations with respect to the predictions of general relativity, although these deviations are generally presumed to be negligible for all practical purposes. Nonetheless, the strength and nature of these deviations remain open questions, given the present uncertainties about the dynamics of quantum gravity. We present here a geometric classification of all spherically symmetric spacetimes that could result from singularity regularization, using a kinematic construction that is both exhaustive and oblivious to the dynamics of the fields involved. Due to the minimal geometric assumptions behind it, this classification encompasses virtually all modified gravity theories, and any theory of quantum gravity in which an effective description in terms of an effective metric is available. The first noteworthy conclusion of our analysis is that the number of independent classes of geometries that can be constructed is remarkably limited, with no more than a handful of qualitatively different possibilities. But our most surprising result is that this catalogue of possibilities clearly demonstrates that the degree of internal consistency and the strength of deviations with respect to general relativity are strongly, and positively, correlated. Hence, either quantum fluctuations of spacetime come to the rescue and solve these internal consistency issues, or singularity regularization will percolate to macroscopic (near-horizon) scales, radically changing our understanding of black holes and opening new opportunities to test quantum gravity.Black holes are nowadays celebrated members of the club of compact astronomical objects. Long gone are the times when the idiosyncrasies of these solutions of the Einstein field equations cast doubts about their physical existence. Indeed, it seems fair to say that there has been a complete shift in the way that these idiosyncrasies are perceived, in particular regarding the accompanying spacetime singularities. Whenever the theoretical concept of a black hole is invoked in order to explain astronomical observations, for instance of the center of our own galaxy, the corresponding holes in the fabric of spacetime that general relativity predicts never raise eyebrows. There is a good mathematical reason for this: all indications show that general relativity does an excellent job of hiding these singularities, as the cosmic censorship hypothesis makes more precise [1]. Moreover, these singularities were never physically expected to be there to start with, as accepting such a singular behaviour seems abhorrent from a physical standpoint. The existence of a mechanism that operates at the fringes of general relativity and rectifies the singular tendencies of the latter, is often (and, in many cases, implicitly) assumed. Whatever price one must pay for...

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Section: Arxiv:190803261v1 [Gr-qc] 8 Aug 2019mentioning

confidence: 99%

Opening the Pandora’s box at the core of black holes

Carballo-Rubio

Filippo

Liberati

et al. 2020

Class. Quantum Grav.

Self Cite

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“…As for the static case analyzed in reference [14], we can define a (radial) "coordinate speed of light":…”

Section: -4 -mentioning

confidence: 99%

“…The existence of a future/past event horizon depends on the presence or absence of an apparent horizon in the limit t → ±∞, that is, event horizon existence depends on whether the limit 2m(±∞)/a exceeds, equals, or is less than unity. We already know from the static case [14], that there is a throat/bounce hypersurface at r = 0. At this hypersurface the induced 3-metric is…”

Section: -4 -mentioning

confidence: 99%

“…Specifically this r = 0 hypersurface is timelike if 2m(w)/a < 1, null (lightlike) if 2m(w)/a = 1, and spacelike if 2m(w)/a > 1. These correspond to a traversable wormhole throat, a one-way null throat, or a "black-bounce" respectively, where now (as opposed to the static discussion of reference [14]) the nature of the throat can change in a w-dependent manner. Because of this feature, the relevant Carter-Penrose diagrams will thus depend on the entire history of the ratio 2m(w)/a over the entire domain w ∈ (−∞, +∞).…”

Section: -4 -mentioning

confidence: 99%

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Vaidya spacetimes, black-bounces, and traversable wormholes

Simpson

Martín–Moruno

Visser

2019

Class. Quantum Grav.

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102

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We consider a non-static evolving version of the regular "black-bounce"/traversable wormhole geometry recently introduced in JCAP02(2019)042. We first re-write the static metric using Eddington-Finkelstein coordinates, and then allow the mass parameter m to depend on the null time coordinate (à la Vaidya). The spacetime metric isHere w = {u, v} denotes suitably defined {outgoing, ingoing} null time coordinates; representing {retarded, advanced} time, while, (at least for a = 0), we allow r ∈ (−∞, +∞). This spacetime is still simple enough to be tractable, and neatly interpolates between Vaidya spacetime, a black-bounce, and a traversable wormhole. We show how this metric can be used to describe several physical situations of particular interest, including a growing black-bounce, a wormhole to black-bounce transition, and the opposite black-bounce to wormhole transition.

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“…Let us stress that we refer to global hyperbolicity in the "strict" sense of existence of a Cauchy hypersurface which is intersected by every inextensible causal curve exactly once. The weaker condition of partial global hyperbolicity[26], in which there is a partial Cauchy hypersurface which is intersected by every inextensible, causal curve at most once, has also been used in explorations of black hole spacetimes[40,41] 4. Even though this result is certainly not new, there is no proof of this proposition in the literature that we are aware of; we have included a proof for completeness.…”

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confidence: 99%

Geodesically complete black holes

et al. 2020

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The 1965 Penrose singularity theorem demonstrates the utterly inevitable and unavoidable formation of spacetime singularities under physically reasonable assumptions, and it remains one of the main results in our understanding of black holes. It is standard lore that quantum gravitational effects will always tame these singularities in black hole interiors. However, the Penrose's theorem provides no clue as to the possible (non-singular) geometries that may be realized in theories beyond general relativity as the result of singularity regularization. In this paper we analyze this problem in spherically symmetric situations, being completely general otherwise, in particular regarding the dynamics of the gravitational and matter fields. Our main result is that, contrary to what one might expect, the set of regular geometries that arises is remarkably limited. We rederive geometries that have been analyzed before, but also uncover some new possibilities. Moreover, the complete catalogue of possibilities that we obtain allows us to draw the novel conclusion that there is a clear tradeoff between internal and external consistency: One has to choose between models that display internal inconsistencies, or models that include significant deviations with respect to general relativity, which should therefore be amenable to observational tests via multi-messenger astrophysics. CONTENTS

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Black-bounce to traversable wormhole

Cited by 261 publications

References 98 publications

Opening the Pandora’s box at the core of black holes

Opening the Pandora’s box at the core of black holes

Vaidya spacetimes, black-bounces, and traversable wormholes

Geodesically complete black holes

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