Unanswered Questions
958 questions with no upvoted or accepted answers
11
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0
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View of the sky from inside a black hole
Consider an observer located at radius $r_o$ from a Schwarzschild black hole of radius $r_s$. The observer may be inside the event horizon ($r_o < r_s$).
Suppose the observer receives a light ray ...
- 1,398
11
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0
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365
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Significance for LQG of Sen's result on entropy of black holes?
Sen 2013 says,
...we apply Euclidean gravity to compute logarithmic corrections to the entropy of various non-extremal black holes in different dimensions [...] For Schwarzschild black holes in ...
CommunityBot
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11
votes
1
answer
455
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Aren't black holes required to exist forever in our frame of reference instead of evaporating?
I know that for an observer far away, nothing ever crosses a black hole horizon (due to time dilation), while in the frame of reference of a falling observer the horizon is nothing special on its way ...
- 2,083
10
votes
2
answers
934
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Conservation of Komar mass
The definition of Komar mass in GR is associated with one asymptotically flat end. However, a hypersurface may contain more than one end, such as the spacelike Einstein-Rosen bridge in Kruskal ...
CommunityBot
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10
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0
answers
295
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What really are exotic supersymmetric black holes?
I have just read (in the black holes chapter 14 on p244 of this book Ref.1) that in string theory, when one adds an (electric?) charge $Q$ to a static black hole, one can arrive at an exotic ...
- 746
10
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500
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Can a nearly-extremal black hole be stable against Schwinger vacuum breakdown?
I was doing some basic algebra to estimate the range of possible masses $M$ and electric charge $Q$ for a nearly extremal Reissner-Noström black hole. I want to see if the logic is correct
the ...
- 14.5k
10
votes
0
answers
259
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Can we have consistent histories inside a black hole?
A consistent history is a POVM set of observables corresponding to a time-ordered product of projection operators. For gauge theories, not any old operator will do, only gauge-invariant observables. ...
- 3,745
9
votes
3
answers
331
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Quantum pressure and chemical potential for a Schwarzschild black hole?
Just as Hawking showed that even Schwarzschild black holes have a temperature, shouldn't they also have a pressure and chemical potential? Are there any analytical formulae of those as well as
$$ T_{...
CommunityBot
- 1
9
votes
0
answers
261
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Does Hawking radiation need an apparent horizon and when does it switch on during stellar collapse?
I've read that Hawking radiation is implicitly linked with the existence of an apparent horizon (1). This seems a slightly less onerous than linking Hawking radiation with a genuine bona fide event ...
- 206k
8
votes
0
answers
282
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Does an evaporating black hole violate conservation of angular momentum?
Angular momentum is supposed to be conserved, but when a rotating black hole evaporates the Hawking radiation comes out in straight lines. Doesn't this violate conservation of angular momentum?
Does ...
- 358k
8
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0
answers
187
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Hayden and Preskill's paper "Black holes as mirrors" - Classical model of black hole
If someone's read the "black holes as mirrors" paper by Hayden and Preskill which can be found here , Can you please explain to me how the probability of failure in the classical model of the black ...
- 1,212
8
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0
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104
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Collapse of two large black holes in AdS
In $4d$ flat space, two black holes of mass $M$ can collapse to form another one of (roughly) mass $2M$. This process is spontaneous, as reflected by the fact that the black hole entropy $S=M^2$ ...
8
votes
0
answers
343
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Geometric entropy vs entanglement entropy (dependent on curvature coupling parameter)
I have a quick question. In hep-th/9506066, Larsen and Wilczek calculated the geometric entropy (which I believe is just another name for entanglement entropy) for a non-minimally coupled scalar field ...
- 9,571
7
votes
0
answers
186
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Correct statement of Birkhoff's theorem (spherically symmetric does not imply static?)
If I understand correctly, the appropriate statement of Birkhoff's theorem in general relativity is that
The Schwarzschild metric is the unique spherically symmetric vacuum
solution.
(Or we might ...
- 684
7
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0
answers
291
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Relation between maximally mixed state and thermal state
Hawking calculated the density matrix of the outgoing radiation to be a thermal state. I have heard people say this is a maximally mixed state. Is this because given a fixed average energy in the ...
- 206k