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3
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1answer
155 views

Does all matter emit gravitational waves all the time?

I understand that gravitational force is a result of the curvature of spacetime and that the analogy with electromagnetic waves falls apart at a certain point. However, I have been confused when ...
3
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1answer
95 views

Why are nonrelativistic methods used in binary pulsar systems (gravitational waves)?

Although gravitational waves are a subject of the General Relativity, why do most books use Newtonian equations of motion for power radiated and rate of change of eccentricity calculations? In most ...
2
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1answer
82 views

The ADM Energy of Gravitational Waves?

I have been looking for books about this question for several days. However, almost all books use Landau–Lifshitz pseudotensor to calculate the energy of Gravitational Waves.And they said the result ...
0
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1answer
25 views

Why doesn't linear wave theory produce phase velocities that agree with each other?

I'm not sure I understand the dispersion relationship for water waves. According to Wikipedia, the wavelength of ocean wave at arbitrary depth is given by: \begin{equation} ...
7
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0answers
236 views

Monopole Gravitational waves exist?

GR says that monopole gravitational radiation does not exist. I understand the reasons for this. However there is this effect (which seems to me to have the hallmarks of a wave). Paper at arXiv: ...
5
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0answers
286 views

Energy-Momentum Tensor of a Gravitational Wave

In radiation gauge ($\gamma=0$), the Einstein field equation in vacuum for a perturbation $\gamma_{\mu\nu}:=g_{\mu\nu}-\eta_{\mu\nu}$ is given by $$ \boxed{ \partial^\alpha\partial_\alpha ...
5
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0answers
117 views

What are the current experimental restrictions of the possible speeds of gravitation?

Somewhere I read that the Hulse-taylor binary pulsar can not differentiate between competing theories assuming different speeds of gravity. Is it mathematically true in general, that the orbital decay ...
3
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0answers
47 views

What are the alternative explanations for the indirect evidence of gravitational waves?

Even though the consensus is that gravitational waves almost definitely exist, it has been well documented that there is no direct evidence. My question; what are the alternatives to gravitational ...
3
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0answers
44 views

How do inflationary models predict the generation of gravitational waves during the inflationary period?

Recent results from the BICEP2 experiment have produced a lot of talk about the primordial gravitational waves produced during the inflationary period. I would like to have some explanation about how ...
3
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0answers
134 views

Computing linearized gravitational wave emission from point-like masses

I'm trying to compute the gravitational wavefront created from a set of moving masses. I'm trying to apply the equation $$ h_{jk} = \frac{2}{r} \frac{d^2 Q_{jk}}{dt^2}$$ Where $h$ is the linearized ...
3
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0answers
169 views

What does BICEP2's results tell us about gravitation waves and quantum gravity?

The BICEP2 results, unless I am mistaken, are a measurement of CMB polarization, i.e. photon polarization. That is, taken at face value they say nothing about gravity directly. Now, we can start to ...
2
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0answers
37 views

Maximum Power transmitted using General Relativity waves - cf Schwinger limit

In Electromagnetism, QED says that the linearity of Maxwell's equations comes to an end when field strengths approach the Schwinger limit. Its about 10^18 V/m. What is the corresponding formula for ...
2
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0answers
57 views

Can a gravitational wave produce oscillating time dilation?

I was reading about gravitational waves and about laser based detectors. I also read this. As mentioned in the answer, when ever there is a deformation in spacetime, doesn't it also create a minute ...
1
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0answers
37 views

Colliding black holes to an outside observer

We know that a particle approaching an event horizon will appear to an outside observer to slow down and never cross the horizon. What is observed by an outside observer when a singularity ...
1
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0answers
22 views

How close would you have to be to the merger of two black holes, for the effects of gravitational waves to be detected without instruments?

Assume two black holes in the most common size range, spiraling into each other until they merge. The event releases significant amounts of energy via gravitational waves, which warp the space-time. ...
1
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0answers
39 views

For gravitational wave from twin stars, how was the tidal effect counted?

As the primary indirect evidence, the work on calculating the rotational slow down earned the 1993 Nobel prize. However, I cannot find any where mention how the work deal with the tidal effect. Are ...
0
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0answers
25 views

Differential precession due to gravitational waves

To motivate the question, Andy Strominger recently put out a paper on calculating the Sagnac shift of counterrotating beams due to the angular momentum flux of a passing gravitational wave. See ...
0
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0answers
37 views

Generalized long wave and KdV equation

I have read many papers about benjamin-bona-mahony (BBM) equation or Regularized Long Wave (RLW) equation and found that BBM equation can be derived from KdV equation. from other papers i got others ...
0
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0answers
45 views

Transverse Trace-less quadrupole

In Gravitational radiation, it is convenient to work with "transverse traceless quadrupole tensor". However there are three terms: "quadrupole moments" , "reduced quadrupole moment" and "transverse ...
0
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0answers
48 views

Would a directional “graviton” emitter violate any known laws of physics?

Setting aside that we don't known what the mediating partial in quantum gravity looks like and have no way to manipulate it, what would the implications be of a directional graviton source be? Would ...
0
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0answers
54 views

What are the implications of the possibility that the BICEP2 results are caused by a self ordering scalar field transition?

I've found this interesting paper that mentions another possible way to interpret the recent BICEP2 results, and that hadn't been ruled out yet 1. As interesting as the possibility that the BICEP2 ...
0
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0answers
70 views

One more time about the connection of Weyl tensor and gravitational waves

There is differential identity with Weyl tensor and energy-momentum tensor: $$ D^{\lambda}C_{\lambda \alpha \sigma \beta} = 4 \pi G \left(D_{\sigma}T_{\alpha \beta} - D_{\beta}T_{\alpha \sigma} + ...
0
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0answers
98 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
57 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
79 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 ...