Questions tagged [cosmic-censorship]

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Cosmic censorship conjecture: Why naked singularities are expected not to exist?

According to wikipedia, the weak form of the Cosmic Censorship Hypothesis says the following: Singularities [...] are typically hidden within event horizons, and therefore cannot be observed from the ...
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Is there physical reason for a stably causal spacetime, or the existence of a Cauchy surface?

In their 1979 essay Global structure of spacetimes, Geroch and Horowitz describe methods of determining the topology, causal structure and singularity of spacetimes. Their (mathematical) arguments are ...
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Book recommendation on gravitational collapse

Does anyone know any books or lecture notes which cover the topic of gravitational collapse assuming intermediate knowledge of general relativity? I wish it covers topics like the spherical collapse ...
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Schwarzschild Naked Singularity Creation

In the Schwarzschild metrics (Plank units): $$ds^2=-\left(1-\frac{2m}{r}\right)dt^2+\left(1-\frac{2m}{r}\right)^{-1}dr^2+r^2\left(d\theta^2+\sin^{2}\theta d\phi^{2}\right),$$ we can have a Black Hole (...
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Why do physicists dislike Naked singularities? [duplicate]

Why do physicists dislike naked singularities? Why do physicists consider the potential existence of Naked singularities as a serious problem?
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If the weak energy condition is violated, can the area of ​the event horizon decrease?

The second law of black hole mechanics asserts $$\text{WCC} + \text{WEC}\Longrightarrow\delta A \geq 0 \tag{1}$$ where WCC = weak cosmic censorship, WEC = weak energy condition and A = event ...
Alessandro Rovetta's user avatar
7 votes
2 answers
722 views

Naked singularity

Many consider naked singularities as a fundamental problem and that it should be always covered by a horizon (Cosmic censorship hypothesis). But why naked singularities are really a problem? If we ...
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Are singularities' behaviour really unpredictable?

If a real/true singularity existed our models and theories would become useless to predict what would happen in that singularity. For example if naked singularities really existed, we could not ...
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1 answer
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Would a 5-dimensional black hole actually break laws of physics?

I discovered a paper by, Figueras, Kunesch, and Tunyasuvunakool, "End Point of Black Ring Instabilities and the Weak Cosmic Censorship Conjecture." A Cambridge University press release is here. The ...
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Electron falling into an extreme black hole and Cosmic Censorship Hypothesis [duplicate]

It is argued that a black hole with Q>M cannot be formed as the formation of such a black hole leaves a naked singularity which is against the Cosmic Censorship Hypothesis. But, consider an extreme ...
Rajath Radhakrishnan's user avatar
5 votes
1 answer
267 views

Can BMS Supertranslations Make a Black Hole Naked?

I recently learned that the BMS supertranslations actually add hairs to black holes and physically change the metric. In such a scenario, I am very curious to know if the black hole can be overcharged ...
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Naked Singularities Out of Extremal Black Holes?

Consider a pair of identical extremal black holes at rest. It is a fact that they exert no net force on each other and remain in static equilibrium. Now, clearly, each of the black holes is in ...
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Why Do Extremal Black Holes Not Radiate?

This might be a "metaphysical" question with no actual physics content and if such is the case then I apologize. Actually, to figure out whether or not it is an actual physics question is one of the ...
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8 votes
1 answer
881 views

What is the current status of cosmic censorship?

Cosmic censorship is a vaguely defined research program dating back to conjectures by Roger Penrose in the 1970s. Part of the research program is to search for useful ways to define cosmic censorship, ...
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3 votes
1 answer
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Naked singularity of a charged black hole

Consider the Reissner-Nordstrom metric for a black hole: $$ds^{2} = - f(r)dt^{2} + \frac{dr^{2}}{f(r)} + r^{2}d\Omega_{2}^{2},$$ where $$f(r) = 1-\frac{2M}{r}+\frac{Q^{2}}{r^{2}}.$$ We can write $...
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Does Violating Cosmic Censorship Really Mean Violating Causality?

As I understand it, the basic motivation behind ruling out a naked singularity is that we don't know what is happening at a singularity and thus, we won't be able to predict anything in the universe ...
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A Universal Upper Limit on Mass Within a Radius $R$?

Since the universe has a positive cosmological constant, there is an upper limit on the mass of the black holes as evident from the so-called Schwarzschild-de Sitter metric: $ds^2 = -f(r)dt^2 + \...
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4 votes
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Does the cosmic censorship conjecture limit the charge/mass ratio for particles?

For charged black holes, supposing true the cosmic censorship conjecture, this inequality must be verified (in natural units): $GM^2 > Q^2$ Where of course $M$ and $Q$ are the mass and charge of ...
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Can a computer grow in memory without bounds? [closed]

As far as I know, current cosmological models predict an infinite universe. This leaves me wondering, given our current understand of cosmology: Can a hypothetical cosmological-scale computer keep ...
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How can a five-dimensional black hole 'break' general relativity? [closed]

By the laws of general relativity and the existence of black holes, what makes our universe to be just 4 dimensional but not 5 or more because a 5-d black hole can violate theory of relativity? ...
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What's the escape velocity of Naked Singularities?

Penrose's Cosmic Censorship Hypothesis doesn't hold for naked singularities which means that at least light can escape the singularity. But, if we calculate escape velocity with the given mass only, ...
Earth is a Spoon's user avatar
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1 answer
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Does cosmic censorship rule out stable toroidal black holes? How?

I'm having a hard time understanding what the arguments against stable toroidal black holes are saying. For many of these, I can't figure out if they're talking about: A non-rotating toroidal event ...
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16 votes
1 answer
1k views

Current status of Penrose-Hawking "thunderbolts?"

I recently came across the interesting statement that most definitions of cosmic censorship (CC), and most work on proving it, don't exclude something that Hawking calls a "thunderbolt" (Penrose 1978, ...
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28 votes
1 answer
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Overcharging a black hole

Hubeny's 1998 paper got a lot of people interested in determining whether cosmic censorship can be violated by dropping too much charge onto a black hole. It suggested that you might be able to get a ...
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6 votes
1 answer
606 views

How is the direction of time determined in general relativity?

In special relativity every frame has its own unique time axis, represented in Minkowski diagrams by a fan-out of time vectors that grows infinitely dense as you approach the surface of the light cone ...
Terry Bollinger's user avatar
3 votes
1 answer
528 views

Why does the cosmic censorship conjecture hold so well?

Why does the cosmic censorship conjecture hold so well? Penrose proposed spacelike singularities and closed timelike curves are always hidden behind event horizons in general relativity. His ...
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3 votes
3 answers
2k views

Shouldn't stars disappear from our view due to expansion?

The currently accepted theory of the expansion of the universe would suggest that for any point in the universe, there is a 'boundary' (somewhat like the Schwarzschild radius) beyond which it cannot ...
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Understanding difficulty with proving strong cosmic censorship theorems

I want to get a grip about the technical problems related to proving Penrose conjecture Intuitively, it seems it should not be too difficult; just start by classifying it in 0-dimensional (i.e: ...
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12 votes
1 answer
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Relationship between Weak Cosmic Censorship and Topological Censorship

The weak cosmic censorship states that any singularity cannot be in the causual past of null infinity (reference). The topological censorship hypothesis states that in a globally hyperbolic, ...
Benjamin Horowitz's user avatar
12 votes
5 answers
1k views

How important is the cosmic censorship conjecture?

I would like to know how important the cosmic censorship conjecture is? Should/must a quantum theory of gravity obey this? It was never rigorously proved in classical GR too. What would be the ...
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