All Questions
Tagged with black-holes event-horizon
173
questions with no upvoted or accepted answers
9
votes
0
answers
262
views
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 ...
- 1,083
6
votes
0
answers
262
views
Why are there multiple universes in the Reissner-Nordström solution?
I am trying to make sense of the Penrose diagram of a non extremal Reissner-Nordström spacetime, that is, the solution with two horizons. The coordinates are
$$ v'=\text{exp}\left(\frac{r_+-r_-}{2r_+^...
- 873
6
votes
0
answers
122
views
Growth of apparent horizons and null convergence condition
An apparent horion ( S. W. Hawking & G. F. R. Ellis (1975). The large scale structure of space-time.) in General Relativity is a surface where all null vectors are pointing "inwards", i....
6
votes
1
answer
440
views
Could harm due to spaghettification be mitigated by entering a black hole at almost the speed of light?
Say that we wanted to send a probe into a black hole, perhaps hoping to see if it's actually a wormhole that might transport the probe elsewhere.
Upon approaching a black hole, the probe would undergo ...
6
votes
1
answer
337
views
Black Holes and QED
So, in quantum electrodynamics (at least to my rudimentary knowledge), the electromagnetic force is mediated by photons.
On the other hand, in classical general relativity, the Kerr Black Hole ...
5
votes
0
answers
319
views
Is the Casimir effect also present between two event horizons?
A follow-up to this question:
Is the Casimir effect also present between two event horizons?
- 982
5
votes
0
answers
2k
views
Further explanation of the Penrose Conjecture
I'm currently a third year maths undergrad, writing a dissertation on the application of minimal surfaces in space.
I have recently come across the Penrose Conjecture that the mass of a spacetime is:
...
- 615
5
votes
0
answers
301
views
Why can apparent horizon be computed based on its local geometry?
Why can apparent horizon be computed based on its local geometry? In the paper titled Black Holes, Geometric Flows, and the Penrose Inequality in General Relativity by Hubert L. Bray, has been written:...
- 584
5
votes
0
answers
457
views
Euclidean black hole extrinsic curvature
I have read that the extrinsic curvature at the horizon of a euclidean black hole is zero? Does anybody know how this can be shown?
- 321
4
votes
0
answers
59
views
Can wormhole inside a black hole become an escape?
I did not major in Physics so not sure if this is a proper question; but according to some Google search there do exist papers discussing wormhole inside black hole like this, which I am not able to ...
- 141
4
votes
1
answer
169
views
How are objects inside a black hole affected by the gravity of objects outside the black hole?
There are many Q&As about whether something inside a black hole can escape the event horizon if another massive object gets close enough to pull it out. I realize the answer (I think universally ...
- 450
4
votes
0
answers
84
views
Conformal Diagram for Astrophysical Black Hole
I have a question about the conformal diagram of an ‘astrophysical’ black hole which forms in finite time (but with no evaporation).
Usually I see the conformal diagram presented as something similar ...
- 55
4
votes
0
answers
513
views
If vacuum decay was somehow triggered inside a black hole, would the rest of the universe notice?
If vacuum decay is triggered, it will spread (at maximum) at the speed of light. But the spacetime inside a black hole is causally disconnected from the space outside. Nothing that happens inside the ...
- 1,405
4
votes
0
answers
221
views
Merging black holes: from two singularities to a ring singularity?
In rotating black holes, the singularity is believed to be a ring or torus, unlike the single-point singularity of a non-rotating black hole.
Topological change - Imagine we have two distant black ...
- 71
4
votes
0
answers
75
views
Images on the event horizon of a black hole as the black hole grows
My layperson's understanding is that when an object falls into a black hole, outside observers see a progressively-redshifted image of the object at the event horizon. What happens to that image as ...
