How Not to Extract Information From Black Holes: Cosmic Censorship as a Guiding Principle

Di Gennaro, Sofia; Ong, Yen Chin

doi:10.48550/arxiv.2103.05516

Cited by 3 publications

(3 citation statements)

References 64 publications

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“…Marolf [34] has pointed out that, in the case of near-extremal black holes, a singularity located at the erstwhile Cauchy horizon is extremely close to the outer horizon, in the sense that an object (with an energy per unit mass which is not very small) falling through the event horizon will reach the singularity almost instantly. (See [35] for a recent discussion of this and related claims.) This is interesting for a variety of reasons.…”

Section: Just Under the Event Horizonmentioning

confidence: 98%

The Special Role of Toroidal Black Holes in Holography

McInnes¹

2022

Preprint

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Grinberg and Maldacena have recently used certain thermal one-point functions, evaluated outside an AdS black hole, to determine the proper time of fall from the event horizon to the singularity (in the uncharged case) or to the Cauchy horizon (in the charged, unperturbed case). This raises the hope that one can use data outside the black hole to investigate the claim that black holes "have no interiors", by proving that the time of fall is exceptionally short, perhaps effectively zero. We examine this question for the particularly interesting case of a black hole (with a flat, toroidal event horizon) emitted by a larger black hole, after the manner postulated by the Weak Gravity Conjecture. We find that the proper time of fall to the Cauchy horizon is indeed always very short for these black holes, so they are prime candidates for an investigation of this kind.

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Section: Just Under the Event Horizonmentioning

confidence: 98%

The Special Role of Toroidal Black Holes in Holography

McInnes¹

2022

Preprint

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“…Furthermore, this example provides an indirect, but strong, evidence that cosmic censorship remains relevant at least in the low energy limit of quantum gravity. (Di Gennaro and I also conjectured in [61] that as any black hole undergoes Hawking evaporation, its parameters should evolve in such a way that it avoids becoming extremal, not just avoid becoming a truly naked singularity. This could be used as a guide to rule out non-standard models of Hawking evaporation.)…”

Section: The Roles Of Singularities and Why They Might Persist In Qua...mentioning

confidence: 99%

On Black Hole Thermodynamics, Singularity, and Gravitational Entropy

Ong

2022

Preprint

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Black holes were found to possess properties that mirror ordinary thermodynamical systems in the landmark paper by Bardeen, Carter and Hawking almost half a century ago. Since then much progress has been made, but many fundamental issues remain. For example, what are the underlying degrees of freedom of a black hole horizon that give rise to said thermodynamical properties? Furthermore, classical black holes also harbor a spacetime singularity. Although it is often believed that quantum gravity would "cure" the singularity, as emphasized by Penrose, this viewpoint requires a deeper examination. In this review, I will examine the possibility that singularities remain in quantum gravity, the roles they may play, and the possible links between singularity and black hole thermodynamics. I will also discuss how -inspired by Penrose's Weyl curvature hypothesis -gravitational entropy for a black hole can be defined using curvature invariants, and the surprising implication that the entropy of black holes in different theories of gravity are different manifestations of spacetime curvature, i.e., their underlying microstructures could be different. Finally, I review the "Hookean law" recently established for singly rotating Myers-Perry black holes (including 4-dimensional Kerr black holes) that connect black hole fragmentation -a consequence of the second law of black hole thermodynamicswith the maximum "Hookean force", as well as with the thermodynamic geometry of Ruppeiner. This also suggests a new way to study black hole microstructures, and hints at the possibility that some black holes are beyond the Hookean regime (and thus have different microstructures). While examining the remarkable connections between black hole thermodynamics, spacetime singularities and cosmic censorship, as well as gravitational entropy, I shall point out some subtleties, provide some new thoughts, and raise some hard but fundamental questions, including whether black hole thermodynamics is really just "ordinary thermodynamics" or something quite different.

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“…Suppose now that the original, "large" black hole satisfies A/L < 1, is extremal, and continues to obey classical Cosmic Censorship as it emits the smaller black hole. (There are of course strong reasons to believe this in the case of decay by Hawking evaporation, both with regard to electromagnetic charges (see [61] for a recent comprehensive discussion of Hawking radiation and its relation to the WGC) and angular momentum [62]. )…”

Section: Decay Of Extremal Ads 4 -Kerr-newman Black Holesmentioning

confidence: 99%

The Weak Gravity Conjecture Requires the Existence of Exotic AdS Black Holes

McInnes

2021

Preprint

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The Weak Gravity Conjecture requires that it be possible for all (classically stable) extremal black holes to decay. The "black hole version" of the conjecture requires that it should be possible for this to occur through the emission of smaller black holes. We consider this version in the case of extremal AdS 4 -Kerr-Newman black holes which are stable against a superradiant instability. One finds that the emitted black hole must be very exotic, having a direction-dependent causal structure. This is independent of the question as to whether the emitted black hole necessarily violates classical Cosmic Censorship. When the system is embedded in string theory, however, we find that it (probably) does.

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How Not to Extract Information From Black Holes: Cosmic Censorship as a Guiding Principle

Cited by 3 publications

References 64 publications

The Special Role of Toroidal Black Holes in Holography

The Special Role of Toroidal Black Holes in Holography

On Black Hole Thermodynamics, Singularity, and Gravitational Entropy

The Weak Gravity Conjecture Requires the Existence of Exotic AdS Black Holes

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