All Questions
46
questions
2
votes
0
answers
60
views
Under what circumstances can a 4D singularity occur in General Relativity?
I've tried to find on the literature about 4D (single point) singularities, but most of the theorems about singularities pertain to either space-like or time-like singularities, which always have some ...
- 157
26
votes
10
answers
13k
views
How do black holes move if they are just regions in spacetime?
If black holes are just regions of spacetime, how can black holes even move? When matter moves through spacetime, it bends the spacetime around it, but if black holes are just regions of spacetime, ...
- 403
0
votes
2
answers
119
views
Why do we defer to GR when describing black holes rather than rely on QM?
This is a broad question but it's well documented that GR and QM are very well tested in their own domains but they conflict around black holes.
Picture a neutron star slowly accreting matter until it'...
0
votes
1
answer
360
views
Angular Deficit of a Conical Singularity
I'm currently studying the Bonnor solution starting with this paper on Black Diholes. The metric is given by :
$$ ds^2 = \left(1-\frac{2Mr}\Sigma\right)^2 \left[-dt^2 + \frac{\Sigma^4}{(\Delta + (M^2 +...
- 55
1
vote
1
answer
63
views
Non-Compactness in Penrose Singularity
I've been studying singularities in GR, and (obviously), came across PST.
Let us state it as the following:
Let $(M, g)$ be a connected globally hyperbolic
spacetime with a noncompact Cauchy ...
- 487
5
votes
1
answer
236
views
Where does the singularity go in an Einstein-Rosen Bridge?
I've been reading up on some material about black holes and Einstein-Rosen bridges. Generally it is said that a black hole is defined by the event horizon (boundary in space where the gravitational ...
- 53
0
votes
1
answer
151
views
Why do black holes remain? [closed]
When we think about black holes as not containing matter but being regions of warped spacetime, I can't think why they don't revert to being Euclidian space more quickly. This is because I can see how ...
- 740
18
votes
5
answers
7k
views
How does it make sense for the universe to have started from a big bang?
It has been said that the Big Bang started from a singularity. Think about a balloon radially growing over time. Fix a time $t_0, t_1 > 0$, and let $M_0, M_1$ be two balloons at time $t_0, t_1$ ...
- 301
2
votes
3
answers
606
views
Spacetime inside the horizon of a black hole
According to Susskind a bit of information crossing the event horizon of a black hole instantaneously encounters the singularity. Also, time appears to gradually slow down for an object approaching ...
- 51
8
votes
2
answers
619
views
A naïve question about spacetime singularities
Very little that I know about general relativity is that there are solutions of its equations with singularities, and these are interpreted as black holes.
Mathematically, the most widespread kind of ...
- 513
1
vote
0
answers
67
views
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 ...
- 121
13
votes
2
answers
2k
views
Is there a limit to how much spacetime can be curved?
My question is about the fact that general relativity predicts bending of space and time. However, I have not seen anything regarding the limits to how much space or time can be bent.
So my question ...
11
votes
1
answer
2k
views
Do black holes exist in 1+1 dimensional spacetime?
I'm currently working in 1+1 dimensional spacetime and would like to know if black holes can exist in such a manifold? I think they can because the Schwarzchild metric has the coordinate singularity, ...
- 477
1
vote
1
answer
142
views
Are there 3D singularities in general relativity?
In the commonly considered spacetimes with singularities, the singularities - to my knowledge - always have less than 3 spatial dimensions:
The singularity of the Schwarzschild spacetime (describing ...
- 272
6
votes
2
answers
184
views
Could spacetimes have singular manifolds?
Let's take a spacetime as a pair $(M,g)$ where $M$ is the manifold and $g$ the metric.
I've seen that there exist a generalization of manifolds. This generalization consist in accept singularities in ...
