All Questions
589
questions
2
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7
answers
1k
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I can't wrap my head around the idea of matter interacting with spacetime. How is the interaction taking place? [closed]
I have tried Googling this for a long time. I have read many forums on this. But still, it doesn't make sense.
General relativity says that space-time is bent/changes when a massive object is there. ...
1
vote
0
answers
60
views
Is the universe closed or flat?
Apparently there is a tension in the measuring of the curvature of the universe (https://arxiv.org/abs/2307.07475) as apparently in 2018 the Planck collaboration got a series of results consistent ...
- 2,472
2
votes
2
answers
189
views
Can $\mathbb{R}^4$ be globally equipped with a non-trivial non-singular Ricci-flat metric?
I'm self-studying general relativity. I just learned the Schwarzschild metric, which is defined on $\mathbb{R}\times (E^3-O)$. So I got a natural question: does there exist a nontrivial solution (...
- 107
0
votes
0
answers
28
views
Same curvature but different orientation of light cones? [duplicate]
Can there be two regions of spacetime which have the same curvature, but with their light cones oriented in different directions?
In the Stack Exchange question "General Relativity via light ...
1
vote
1
answer
99
views
The apparent dilatation of time in General Relativity
Maybe this a dumb question, but, is the gravitational dilatation of time caused because a particle travelling through a geodesic in a curved space-time must cover a larger distance than the one ...
- 1,525
6
votes
3
answers
2k
views
Is source of space-time curvature necessary?
Einstein field equations have vacuum solutions that (probably) assumes the source of curvature (either energy-momentum tensor or the cosmological constant term or both) is elsewhere. Like, in ...
- 1,161
4
votes
1
answer
156
views
Do neutron stars (or really dense stars) contain more volume inside of them than the expected $V=\frac{4}{3}\pi r^3$?
If I understand correctly neutron stars are so dense that general relativistic effects are not negligible anymore. Does this mean that the volume inside of neutron stars is bigger than we would expect ...
- 2,035
0
votes
0
answers
50
views
How the equivalence principle leads to the idea of curved spacetime? [duplicate]
In wikipedia https://en.wikipedia.org/wiki/Equivalence_principle, there are three forms of equivalence principle ( equivalence of gravitational and inertial mass ) :
Weak version (Galilean) :
The ...
- 317
1
vote
1
answer
464
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Einstein tensor in 2d [duplicate]
Is the Einstein tensor in 2D or 1+1D always zero? If so, why?
I recently installed EinsteinPy and started playing wing different metrics - for the 2D cases the result turned out to be always zero.
- 1,161
0
votes
0
answers
38
views
Expressing curvature invariants ($K_1, I_1, ... $), at any one event, through Synge's WF $\sigma$ (given of each event pair, in a suitable region)
Considering a set $\mathcal S$ of events such that for each pair $p, q \in \mathcal S$ Synge's world function $\sigma$ is defined and the corresponding value $\sigma[ ~ p, q ~ ]$ is given, and such ...
- 4,306
0
votes
1
answer
106
views
Another dimensions [closed]
Just a science ponderer, and pretty much interested in physics. Please guide me if I am wrong.
There have been many statements made by the physicists about the existence of other dimensions (...
- 19
-1
votes
1
answer
106
views
When doing general relativity in practice, how do we choose the appropriate manifold describing the scenario?
The theory only deals with the local curvatures, not the global topology. Hence any manifold with an allowed metric is allowed. These can be infinitely many, especially for negative curvature space-...
- 7,980
2
votes
6
answers
2k
views
Is it possible to describe every possible spacetime in Cartesian coordinates? [duplicate]
Curvature of space-time (in General Relativity) is described using the metric tensor. The metric tensor, however, relies on the choice of coordinates, which is totally arbitrary.
See for example ...
- 93
-1
votes
1
answer
129
views
According the theory of general relativity, what is the role of causality in the changes of the curvature of spacetime? [closed]
In Einstein's equations the curvature of spacetime and energy-momentum-pressure density are correlated. Is it clear when changes in matter energy density affect causally to curvature and when changes ...
- 41
0
votes
1
answer
71
views
Is curvature localised in General Relativity?
Is the curvature of spacetime in General Relativy localised?
- 476