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Overcharging a Black Hole and Cosmic Censorship

General Relativity and Quantum Cosmology · Submitted 17 Aug 1998 · 17 references

Pith's verdict: A real new observation (near-extremal, not extremal, starting point) plus a clean shell no-go, wrapped in an abstract that promises more than the body delivers — and the body knows it.

T0 · AI review

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arXiv IDgr-qc/9808043 (version 1)
Pith IDNDHA5B2F, Pith's permanent record of this paper and its review
CitationVeronika E. Hubeny. "Overcharging a Black Hole and Cosmic Censorship." arXiv:gr-qc/9808043 (1998). https://pith.science/paper/NDHA5B2F
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Referee report
The paper

The paper claims

A single charged particle can, in the test-particle limit, drive a near-extremal Reissner-Nordström black hole past extremality, but the paper's own self-force estimate makes the particle bounce short of the horizon, leaving the censorship

The reading

The paper asks whether a black hole's horizon can be destroyed by dropping in matter that carries more charge than mass. Wald's earlier gedanken experiment said no for an exactly extremal hole, because the particles that would overshoot are precisely the ones the hole refuses to swallow. Hubeny's move is to start slightly below extremality instead, so that the black hole can jump over the extremal bound in one finite step rather than creeping up to it. Working in the test-particle approximation, she writes down an explicit family of parameters in which a radially infalling charge passes the horizon and leaves $M+E < Q+q$, i.e. a naked singularity. She then checks the neglected self-force terms and finds they can be made small in absolute size, but the capture margin is smaller still, and her one worked example reverses the outcome. The shell version of the same experiment, where the calculation is exact by spherical symmetry, fails outright because the shell's own charge repels it before it reaches the horizon.

What carries the argument

The load-bearing object is the radial equation of motion for a charged test particle in ingoing Eddington coordinates, $dot r^2 = frac{1}{m^2}[E + qA_v(r)]^2 - g(r)$ with $A_v = -Q/r$ and $g(r) = 1 - 2M/r + Q^2/r^2$. Capture requires $dot r^2 > 0$ for all $r ge r_+$; overcharging requires $E < Q+q-M$. Combining the two gives a lower bound on the particle charge, $q > r_+ - Q^2$, which is empty at extremality and nonempty just below it. That inequality is the whole mechanism: it says the extremal no-go is a knife-edge case, not a barrier. The second piece of machinery is the epsilon-scaling ansatz that turns the three conditions into a single small parameter, letting the author display simultaneously the $O(e^2)$ capture margin, the $O(e)$ self-force corrections taken from the Quinn-Wald equation, and the $O(e)$ classical radius. For the shell case the analogous object is the junction equation $sqrt{g_{in}+dot R^2} - sqrt{g_{out}+dot R^2} = -m/R$, whose effective potential contains the shell's own self-repulsion and self-attraction terms.

Extended reading notes

Core claim

The paper's central claim is conditional and stated as such: if backreaction can be neglected, a near-extremal Reissner-Nordström black hole can be overcharged by a single charged particle. The construction is explicit. With $M=1$, $Q=1-2e^2$, and particle parameters $q=ae$, $E=ae-2be^2$, $m=ce$ for $a>1$, $1<b<a$, $c<sqrt(a^2-b^2)$, the test-particle radial equation gives $dot r^2(r_m) > 0$ at leading order, so the particle passes $r_+$, and $(M+E)-(Q+q) = -2(b-1)e^2 < 0$, so the final configuration exceeds extremality. The same scaling makes the particle's classical radius $q^2/m = a^2 e/c$ and the relative size of the Quinn-Wald self-force terms arbitrarily small as $e to 0$. The paper is explicit that this does not settle the question. The capture margin is $O(e^2)$ while the radiation-damping correction is $O(e)$, so the correction is not small compared with the margin; the single numerical example ($Q=0.99999$, $q=3times10^{-3}$, $m=1.8times10^{-3}$, $E=2.9897times10^{-3}$) shows the corrected $dot r^2$ turning negative, i.e. a bounce. A 'best case' rescue in which all radiated energy escapes requires a starting energy of about $0.0122$ and appears to allow capture, but the author notes the linearized energy integral is unreliable near the horizon, where the correction ratio grows like $e^2/(r-1)^2$ and reaches order one. The companion shell calculation is exact and negative: for an imploding charged shell, the condition $dot R^2(r_m)>0$ is algebraically incompatible with overcharging, and the less stringent condition $d dot R^2/dr(r_+)>0$ is incompatible with the physical bound $0<m^2<E^2$, so the shell bounces outside the horizon.

Load-bearing premise

The argument needs the neglected self-force terms to be negligible for the outcome, but the paper's own scaling shows the capture margin shrinks faster than the corrections do, so smallness relative to the leading terms does not deliver smallness relative to what the process has to overcome.

Editorial extensions

If this is right

  • The extremal no-go for charged-particle capture is not a barrier but a limiting case: any black hole even slightly below extremality admits a finite window of particle charges and energies that overshoot the bound in the test limit.
  • Whether cosmic censorship survives in this scenario cannot be decided by comparing the size of backreaction terms to the size of the leading terms; the relevant comparison is to the capture margin, and the paper's own scaling shows the margin loses.
  • For a charged imploding shell, censorship is upheld without approximation, because the shell's electromagnetic self-repulsion prevents it from crossing the horizon whenever the parameters would overcharge the hole.
  • Any claim that a near-extremal hole can be destroyed must specify the fate of the energy radiated during the infall, since the final mass depends on how much of that radiation is recaptured.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The paper's structure suggests a general lesson for gedanken experiments: an experiment whose success margin scales as one power of a small parameter higher than its own error terms is undecidable at that order, and the honest verdict is 'not resolved' rather than either 'censorship holds' or 'censorship fails'.
  • The contrast between the point particle and the shell points to a one-parameter family interpolating between them, a ring of $N$ symmetrically placed particles, where self-repulsion is diluted by a factor of order $N$ while self-force corrections persist; the paper reports exploratory checks for $N=2,4,6$ but does not settle the backreaction question there.
  • The uncharged rotating analogue, a spinning particle dropped into a near-extremal Kerr hole, removes the electromagnetic self-force that dominates the obstruction here and would be a cleaner place to look for a definite answer.
  • If the bounce found in the worked example is generic rather than an artifact of the linearized energy integral, then the near-horizon energy loss acts as a self-regulating mechanism that keeps the horizon intact without any appeal to a new principle.
Original abstract

We show that, contrary to a widespread belief, one can overcharge a near extremal Reissner-Nordstrom black hole by throwing in a charged particle, as long as the backreaction effects may be considered negligible. Furthermore, we find that we can make the particle's classical radius, mass, and charge, as well as the relative size of the backreaction terms arbitrarily small, by adjusting the parameters corresponding to the particle appropriately. This suggests that the question of cosmic censorship is still not wholly resolved even in this simple scenario. We contrast this with attempting to overcharge a black hole with a charged imploding shell, where we find that cosmic censorship is upheld. We also briefly comment on a number of possible extensions.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 4,267 input tokens, $0.0002 reported.

What the abstract itself states, as probabilities: claims first 0.04 · states limitation 0.82 · human participants 0.01 · controlled comparison 0.26 · randomized assignment 0.01 · states quantitative result 0.07 · compares with prior results 0.93 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

We show that, contrary to a widespread belief, one can overcharge a near extremal Reissner-Nordstrom black hole by throwing in a charged particle, as long as the backreaction effects may be considered negligible. Furthermore, we find that we can make the particle's classical radius, mass, and charge, as well as the relative size of the backreaction terms arbitrarily small, by adjusting the parameters corresponding to the particle appropriately. This suggests that the question of cosmic censorship is still not wholly resolved even in this simple scenario. We contrast this with attempting to overcharge a black hole with a charged imploding shell, where we find that cosmic censorship is upheld. We also briefly comment on a number of possible extensions.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 We show that, contrary to a widespread belief, one can overcharge a near extremal Reissner-Nordstrom black hole by throwing in a charged particle, as long as the backreaction effects may be considered negligible. result 0.99 0.92 0.89 asserted 0.92
s1 Furthermore, we find that we can make the particle's classical radius, mass, and charge, as well as the relative size of the backreaction terms arbitrarily small, by adjusting the parameters corresponding to the particle appropriately. result 0.99 0.95 0.09 asserted 0.99
s2 This suggests that the question of cosmic censorship is still not wholly resolved even in this simple scenario. interpretation 1.00 0.31 0.48 hedged possibility 1.00
s3 We contrast this with attempting to overcharge a black hole with a charged imploding shell, where we find that cosmic censorship is upheld. result 0.98 0.94 0.07 asserted 1.00
s4 We also briefly comment on a number of possible extensions. future work 0.97 0.53 0.02 unclear 0.91

What kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 0.98.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures
Figure 1. Figures.nb 1
Figure 2. Figures.nb 1
Figure 3. Figures.nb 1

Figures reproduced from arXiv:gr-qc/9808043 by the authors.

References
How later papers used it

76 later papers cite it

Evidence: substantial. 76 of the citing papers share no author with it, and 12 of those carry a confident label from Pith's citation classifier.

Pith read 19 of the 128 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Builds on it 1 of 2 papers with this label
How the literature uses it

61 arXiv papers cite this in 102 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 61 sentences without a confident label

Contests it 2 papers
Builds on it 1 paper
  • The equations of motion for charged timelike shells in asymptotically flat black hole backgrounds were previously studied in [ref] and here we generalize them to the asymptotically AdS case.

    Bouncing inside the horizon and scrambling delays · Massive charged shell · 0.99

Uses its method or tool 1 paper
Uses its data or values 1 paper
Compares with it 5 papers
Cites it as background 26 papers

Discussion

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