The gravitational-waves tag has no wiki summary.
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477 views
Are gravitational waves longitudinal or transverse?
Waves are generally classified as either transverse or longitudinal depending on the they way the propagated quantity is oriented with respect to the direction of propagation. Then what is a ...
5
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1answer
96 views
What makes us think we can actually detect gravitational waves?
This refers to the discussion about gravitational waves for the YouTube video LIGO Gravitational Wave Observatory.
I have two questions:
When the gravitational wave passes through the space where ...
5
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2answers
412 views
Can colliding gravitational waves create a black hole?
Whether gravitational waves are real or just a coordinate freedom was argued in the early days of GR. Eventually the conclusion was that they were real. And if they are 'real' then I'm curious if...
...
5
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2answers
184 views
Since there are gravitational lenses, are there gravitational mirrors?
Gravitational lensing is a physical observed effect. Can one have gravitational mirror?
A slightly unrelated question: Can gravitational waves be reflected?
5
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2answers
357 views
Do gravitational waves slow down as they pass through matter?
I've heard that gravitational waves travel at the speed of light, and have some parallels to electromagnetic waves. EM waves slow down as they pass through matter (speed of light in glass is slower ...
5
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1answer
155 views
What is the status of existing measurements of the speed of gravity?
In replying to a recent question I stated:
Gravitational waves have not been yet experimentally observed so as to have their velocity measured.
Which after the fact prompted me to try and verify ...
4
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3answers
260 views
Do rotating bodies emit gravitational waves?
Suppose we have a cylinder of mass $m$, radius $R$ and height $h$ in rotation with speed $\omega$ around its symmetry axis with no friction (ideal situation).
I'd expect this cylinder to emit ...
4
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1answer
115 views
Would it be possible to transmit information through gravitational waves?
First thing I've been wondering is how the gravitational field is emitted. Matter emits gravitational waves, and I guess that those waves travel at around the speed of light. If that's not the case, ...
4
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1answer
190 views
Boundary conditions of relativistic wave solutions?
If you take Einstein's field equations,
\begin{equation}
R_{\mu\nu}-\tfrac{1}{2}g_{\mu\nu}R = -\kappa T_{\mu\nu},
\end{equation}
and you insert the metric
\begin{equation}
g_{\mu\nu} = \eta_{\mu\nu} ...
4
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2answers
117 views
Will cosmological gravitational waves be weaker or stronger than astrophysical ones?
Will gravitational waves of cosmological origin be weaker or stronger (higher amplitude $h \simeq\Delta L/L$) than those created from astrophysical sources?
I'm having a real hard time finding the ...
4
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0answers
85 views
What is the status of gravitational wave searches? [closed]
What is the status of gravitational wave searches such as LIGO?
3
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3answers
197 views
Magnetic fields and gravitational waves. How far do they reach?
I read that magnetic fields perpendicular to a current shoot out and expand all the way to infinity.
Additionally a gravitational wave, no matter how small will also expand to infinity at the velocity ...
3
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1answer
298 views
Gravitational waves as dark energy?
Is the energy carried by gravitational radiation a viable candidate for $\Lambda$ / dark energy?
3
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2answers
120 views
How can I tell if a system has a quadrupole moment?
We know that gravitational waves are emitted (at least in GR) when the system has a time-varying quadrupole (or higher) moment. My question is
Is it possible to easily tell (e.g. just by looking) if ...
3
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1answer
63 views
Can extremely charged objects simulate some black hole effects?
If we had a positive point charge of incredible quantity, does there exist an imaginary sphere about it, such that regardless of the initial speed and direction of any electron, that electron could ...
3
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1answer
172 views
Event Horizon fluctuating due to gravitational waves
Do the interiors of black-holes create gravitational waves and if so do these waves cause the radius of the event horizon to fluctuate as the waves pass the horizon ?
3
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0answers
95 views
Would warp bubbles emit gravitational Cerenkov radiation in general relativity?
Inspired by the gravtiomagnetic analogy, I would expect that just as a charged tachyon would emit normal (electromagetic) Cerenkov radiation, any mass-carrying warp drive would emit gravitational ...
2
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3answers
418 views
Why is $\langle \partial_{\mu} f(x) \rangle=0$?
I'm reading page 488 of Hobson, Efstathiou & Lasenby, and I don't understand something they write... so I came here.
The concept they describe is in linearised general relativity. In particular, ...
2
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2answers
163 views
Gravity waves detection, any news?
Is the detection of gravity waves a reality with nowdays technology ?
Are there recent news ?
2
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1answer
102 views
variations of Einstein equations with conversion between gravitational and non-gravitational energy
I'm looking for existing papers studying a variation to Einstein equation that does not rely on the annoying matter conservation identity:
$$ T_{\mu \nu; \nu} = 0 $$
And instead tries to equate the ...
2
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1answer
78 views
Gravity waves detectors; are they all similar?
Are the gravity waves detectors all working on the same
principle/effect ?
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2answers
214 views
How does gravitation propagate along curved spacetime?
In this wikipedia article it is described how a beam of light, with its locally constant speed, can travel "faster than light". That is to say it travels a distance, which, from a special relativistic ...
1
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1answer
80 views
Gravitation within galaxies
Do all galaxies radiate gravitational waves? What is the origin of these waves, the origin of the Galactic center? If it exists, do two galaxies warp together due to these waves, when they come ...
1
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1answer
55 views
Why don't gravitational waves free stream
Simply hot dark matter is not allowed due to free streaming. So do gravitational waves:
a) free stream if not why not?-Surely they can since they are relativistic an weakly interacting.
b) if they ...
1
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1answer
106 views
How do gravitational waves sustain and propagate large scale spacetime curvature?
I understand that gravity in GR is a manifestation spacetime curvature dictated by the field equations by the principle that objects follow the geodesic path in spacetime.
And, I get how ...
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0answers
57 views
Thermal gravitational radiation and its detection
To my poor knowledge on the topic, the gravitational waves that are most likely to be detected by LIGO or other experiments do not have thermal spectrum. But I'm not certain.
I know that Hawking's ...
1
vote
1answer
258 views
warp drive with gravitational waves in the nonlinear regime
gravitational waves are strictly transversal (in the linear regime at least), also their amplitudes are tiny even for cosmic scale events like supernovas or binary black holes (at least far away, ...
0
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1answer
59 views
Why must the gravitational wave components be much less than unity?
We start with the metric tensor
\begin{equation}
g_{\mu\nu}(x) = \eta_{\mu\nu} + h_{\mu\nu}(x)
\end{equation}
in the linearised theory, or
\begin{equation}
g_{\mu\nu}(x) = \bar{g}_{\mu\nu}(x) + ...
0
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2answers
83 views
Theory that gets rid of gravitional wave
Is there any theory that gets rid of gravitational wave and still matches with all correct predictions made by standard physics theories? (e.g. General Relativity)
0
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1answer
34 views
Is weak lensing the statistical effect of microlensing?
I am looking into the effects of gravitational lensing of gravitational waves. I know that gravitons travel along null geodesics, just as photons, and so they will suffer the same deflection angle by ...
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0answers
54 views
Counterpart of the Klein Gordon Equation on the “Coordinate Shell”
The relation
$$\psi=Ce^{i/\hbar(Et-\mathbf{p}\cdot\mathbf{x})}\tag{1}$$
satisfies the Klein Gordon equation on the mass shell, i.e. for $E^2=p^2+m^2$.
Now let's think in the reverse direction.
...
0
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0answers
39 views
Emitting gravitational radiation
Is the following true:
Two massive bodies with variable distance between them do not emit GR in any direction
Two bodies that revolve around common center will not emit in the plane of their orbits
...
0
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0answers
66 views
Does quantum field theory accept gravitational wave?
Does quantum field theory accept gravitational wave? As quantum field theory is flat spacetime theory, I wonder whether gravitational wave would be true.
Does contemporary string theory variants ...
-5
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1answer
68 views
Is it possible that a gravitational wave of space - time hit the solar system?
I went (on vacation) to the beach, The sea was very calm (just like solar system) There was one person in a fishing boat, Suddenly a huge wave came to shore...
Is it possible that a gravitational ...
