Questions tagged [gravitational-waves]
For questions about the propagation of waves carried by space-time, for instance as described by general relativity. Not to be confused with gravity waves, such as ocean surface waves.
1,082
questions
0
votes
0
answers
30
views
Why quantum gravity can't be described by spin-1 bosons? [duplicate]
As the title suggests, why quantum gravity can't be described by spin-1 gravitons?
- 473
1
vote
1
answer
101
views
Could Dark Matter Be Fully or Partially Explained by Gravitational Waves?
This is something I have wondered for a long time and cannot see why it is not a possible solution. Basically, any motion of matter (Mass may be a more accurate description here) through space time ...
1
vote
1
answer
56
views
Would a gravitational wave accelerate a single ball?
Suppose I have two balls floating in space. If a gravitational wave with the correct polarization passed by, it would create an oscillating strain causing the balls to accelerate together, then apart, ...
- 101
0
votes
0
answers
39
views
Is there some mathematical or physical model that postulates that gravitons exist? [duplicate]
Is there some model, mathematical or physical, that postulates that gravitons exist? For example is there mass missing from some particle decay that is thought to form gravitons? Or something in the ...
- 3,682
3
votes
1
answer
64
views
How much energy from gravitatational waves does the sun absorb?
I was wondering how much energy from gravitational waves the sun could absorb since it is so big and also has a massive gravitational pull. Is it possible for the sun to trap gravitational waves ...
- 776
0
votes
1
answer
118
views
In pure GR can a black hole spontaneously appear?
In a universe without matter and just gravitation fields, can a black hole spontaneously appear? I would assume it could since such a black hole would evaporate purely into high energy gravitons. The ...
- 6,338
0
votes
1
answer
63
views
What defines the speed of waves? [closed]
Why the speed of sound or speed of electromagnetic/gravitational waves have values which they have? What defines it? Why do it not two times slower or two times faster, for i.e.?
- 628
0
votes
2
answers
72
views
I know that gravitational waves are generated by accelerated masses, but do all accelerated masses generate gravitational waves, even small masses?
In other words, is there an accelerated mass that is too small to generate gravitational waves?
- 11
0
votes
1
answer
29
views
Invariance of binary black hole gravitational waves
Why BBH gravitational waves can be parameterized with the mass ratio? (and is not necessary the value of the two masses explicitly)
- 1
1
vote
1
answer
30
views
Difference between Gravitational wave solution in TT gauge vs pp-waves
I am studying gravitational waves and I am trying to understand two types of wave solutions I have seen for the metric. In various texts (Carroll, Wald, etc.), they discuss the gravitational wave ...
- 891
0
votes
0
answers
22
views
High frequency (HF) gravitational wave generator [duplicate]
I see this US patent for a high frequency (HF) gravitational wave generator:
US10322827B2
In the patent they mention virtual photons. Can anyone tell me what a "virtual photon" is?
- 1
2
votes
1
answer
28
views
Do stars lose spin angular momentum, to planets, radiation, or gravitational waves, or in some other way get a longer period?
A spinning star is throwing off stellar wind, and electromagnetic radiation, which might be carrying away angular momentum, so that the star loses angular momentum, and its angular momentum per unit ...
1
vote
0
answers
29
views
GW gauge choice shortcut
When solving the linearised Einstein field equations for gravitational waves, we define the trace reversed metric $\bar{h}_{\mu\nu}$ for which we write the coordinate transformations $x^\mu \...
- 11
5
votes
3
answers
3k
views
What do we mean when we say gravitational waves are non-linear and do not superpose like EM waves?
I have read this question:
Now it's not actually true that general relativity obeys a law of superposition, but it is an extremely good approximation for a small-amplitude gravitational wave passing ...
- 26k
0
votes
2
answers
113
views
Let $Q(t,\vec x)$ solve $\partial_t^2 Q = \nabla^2Q$. Why $\partial_t^2Q = 2 (\partial_r + r^{-1})\partial_{t-r}Q$?
On page 5 of Bondi et. al. (1962) (https://doi.org/10.1098/rspa.1962.0161), a suitable method for solving the gravitational wave equation is demonstrated for the case of the scalar wave equation. ...
- 517
2
votes
1
answer
46
views
Transverse component of distorsion tensor in GR
On pages 164-165 of Eric Gourgoulhon's lecture notes on Numerical Relativity, the author introduces the decomposition (9.49) for the distorsion tensor related to a foliation $(\Sigma_t)_{t\in \mathbb{...
- 249
1
vote
1
answer
62
views
Question about gravitational waves
Gravitational waves are measured by interferometers, in particular by the change in length of one of the arms, with respect to the other. In this scenario, the light that has always the same speed, ...
- 45
0
votes
0
answers
20
views
Gravitational waves strain drop off
For the gravitational waves detected by LIGO back in 14.09.2015, how do we measure how strong the strain from the gravitational waves would be if the collision happened say 1000AU away from Earth? How ...
- 1
0
votes
1
answer
38
views
Does SXS catalog for NR simulations have non-spinning, non-eccentric blackholes?
I am looking for NR waveform for two non-spinning and non-eccentric black hole binary merger for small mass ratio. Somehow, on the SXS catalog website, I don't see any such description.
Thanks
- 119
3
votes
1
answer
29
views
What are the $f$-modes, $g$-modes,...of GW in neutron stars and compact objects?
Reading gravitational wave astronomy papers, sometimes is mentioned the importance and relevance of $f$-modes and $g$-modes of gravitational waves.
What are exactly the $f$-modes/$g$-modes in ...
- 5,697
1
vote
0
answers
101
views
Calculating Gravitational Waves Given Boundary Conditions
How can I calculate the gravitational waves emitted by a system in which the initial and final angular momentums are known? Can you provide me with an explicit example?
Say the system starts at rest ...
1
vote
0
answers
90
views
What is the significance of a constant, $C$ in a damped cosine function? [closed]
I've used to fit some scattered points by an equation of damped cosine with a constant function ($(A\cos({kx})+C)e^{-Bx}$) and that equation fits better than only a damped cosine $A\cos({kx})e^{-Bx}$, ...
- 11
2
votes
0
answers
77
views
Viscous damping in general relativity
In Minkowski spacetime, waves are modeled via the wave equation $$(\partial_t^2-\Delta)u=0.$$ When viscous damping is present, one studies the damped wave equation
$$(\partial_t^2-\Delta+W(x)\...
- 21
0
votes
0
answers
29
views
How do I convert between + and x polarizations of a gravitational wave?
Let's say I have a gravitational waveform h(t) that is completely +-polarized. How do I convert it to one that has some x-component? Or is completely x-polarized?
- 1
0
votes
1
answer
51
views
Number of modes of gravitational waves and dimensionality of spacetime
I'm starting to gather information about general relativity and riemannian geometry (as a former future physicist, I'm more interested in ideas and results than in rigor and mathematical proofs) to ...
- 117
0
votes
1
answer
56
views
Could dark energy be the gravitational force of the perimeter mass expanding faster than speed of light?
Due to inflation in the beginning of the universe, there may be a perimeter mass which expanding faster than speed of light and gravity of inner space can not reach and pull it, but inner space can be ...
1
vote
0
answers
37
views
Gravitational waves and their properties [closed]
To clarify my question. I wanted to ask, "how do I figure out the interference of 2 different gravitational waves?" If we were to spin 2 black holes very quickly and take a cross section of ...
- 95
6
votes
4
answers
912
views
How do gravitational waves propagate?
How do gravitational waves work like water waves? Spacetime isn't supposed to be a surface, it is solid, so how do gravitational waves propagate through it like transverse waves on the surface of ...
- 95
0
votes
2
answers
34
views
As a binary system start producing gravitational waves even before merge should the stars start losing mass while still orbiting each other?
As a binary system start producing gravitational waves even before merge should the stars start losing mass while still orbiting each other? But is this really difficult to understand as just orbiting ...
- 2,105
0
votes
0
answers
33
views
Gravitational waves multipole moments
I have read about Quadrupolemoments of Gravitational waves and found out that they can be calculated via the following formula:
$$
{I}_{ij}^T = \int \rho(\mathbf{x}) \left[r_i r_j - \frac{1}{3} r^2 \...
- 31
1
vote
1
answer
161
views
Calculation of interaction of gravitational waves with a black hole
We have a well understood interacting electromagnetic system, an electromagnetic wave interacting with an atom. We use perturbation theory to calculate what happens in such a system. The result is of ...
- 153
0
votes
0
answers
25
views
Gravitational Waves and Quantum Gravity [duplicate]
Since we can now directly observe gravitational wave signals, can any type of future experiment be set up that might manifest the quantum nature of gravity? For example, perhaps a version of LIGO ...
- 3,685
1
vote
0
answers
22
views
Can gravitational waves be refracted or reflected?
Graviatational waves are influenced by gravitational lensing. But are there other ways to influence gravitational waves?
Could we build reflectors or refracting systems to concentrate gravitational ...
- 712
2
votes
2
answers
91
views
Linearized theory and gravitational waves
I've been reading the chapter about gravitational radiation of Schutz's book.
In one of the sections, he begins with the linearized Einstein's equations and tries to find an intuitive solution:
$$(-\...
- 21
3
votes
1
answer
117
views
Smooth vs analytic spacetimes
Recently in more technical settings (I was learning algebraic QFT), I encountered the term "real analytic" manifolds (Lorentzian manifolds, to be precise). This is in contrast to smooth ...
- 1,518
3
votes
1
answer
95
views
Can point masses following geodesics and orbiting one another emit gravitational radiation?
I am a bit confused about this situation: according to general relativity, when two masses orbit one another, they emit graviational waves, which carry away certain energy. For example, check out ...
6
votes
2
answers
1k
views
How can a pulsar slow down?
I saw in some astronomy textbooks that pulsars gradually slow down due to the loss of energy by its radiation. I wonder why this is possible?
Although the radiation is now not thermal but in the form ...
- 3,854
0
votes
1
answer
34
views
How to convert from polarization modes ($h_{+}$, $h_{×}$) to obtain spin-weighted spherical harmonic $h_{lm}$ as a function of $h_{+}$, $h_{×}$?
This question arises from a discussion in the thread How to convert from plus and cross polarization modes ($h_{+}$, $h_{×}$) to spin-weighted spherical harmonic $h_{lm}$?
I was looking for a ...
- 119
2
votes
1
answer
50
views
How to convert from plus and cross polarization modes ($h_{+}$, $h_{×}$) to spin-weighted spherical harmonic $h_{lm}$?
I was wondering if there is a method to express the $h_{+}$ & $h_{×}$ polarization modes to spin-weighted spherical harmonic $h_{lm}$. I ask this in the context of gravitational waves. We see that ...
- 119
2
votes
1
answer
103
views
Is it possible to distinguish the intensity and the frequency of the graviton?
The wave equation of the graviton was assumed to be similar to that of the EM waves, which a "frequency" parameter could be identified by comparison. However, in EM, there was intensity as ...
- 2,940
0
votes
0
answers
29
views
Angular momentum of gravitational wave
I am thinking about what is spin and angular momentum of gravitational beams. I came up with the answer that spin is intrinsic to a wave and is related to its source. But I can not start thinking of ...
- 67
6
votes
3
answers
733
views
What are the differential equations that model a self-propagating gravitational wave in space-time?
Light is a self-propagating wave, but it's very complicated.
Imagine, if you will, a wave in space-time that by assumption was self-propagating like light, except that it was a gravitational wave.
...
- 203
1
vote
2
answers
66
views
Gravitational wave radiation power from dimensional analysis
Let us try to find a formula for the power emitted through gravitational waves (GW) from a binary system in quasi circular orbit. The relevant quantities are the Newton's constant $G_N$, speed of ...
- 895
1
vote
1
answer
32
views
Single gravitational plane wave or their interference can carry spin angular momentum?
I would be grateful if anybody could tell me if I had one gravitational wave in the form of a plane wave, it still would carry spin angular momentum? We know that gravitational waves are mostly the ...
- 67
0
votes
1
answer
54
views
Why Weyl scalar $\psi_{4}$ has a spin weight -2?
In the Newmann-Penrose formalism , Weyl scalar $\psi_{4}$ is given by $\psi_{4} = C_{a b c d} n^{a} \bar m^{b} n^{c} \bar m^{d}$, where $C_{a b c d}$ are weyl tensor components and $n^{a}$, $\bar m^{...
- 175
0
votes
0
answers
33
views
Distance to source of GW 150914
Looking at the original paper on this gravitational wave, PRL 116, 06112 (2016), it is difficult to determine how they estimated the distance to the source. Can anyone provide some explanation? They ...
- 309
5
votes
1
answer
359
views
Excluding the case of a neutron star-black hole merger with gravitational wave GW 150914
The paper from LIGO's original gravitational wave detection (PRL 116, 061102 (2016)) defines the chirp mass as
$$M=\frac{(m_1 m_2)^{3/5}}{(m_1+m_2)^{1/5}}=\frac{c^3}{G}\left[\frac{5}{96}\pi^{-8/3}f^{-...
- 309
0
votes
0
answers
118
views
Gravitational wave propagating in $x$-$y$ plane with angle $\theta$ with $x$-axis
I am going to ask a question related to a paper called "Spin angular momentum of gravitational wave interference" which its link is: https://doi.org/10.1088/1367-2630/abf23f. My question is ...
- 67
17
votes
2
answers
2k
views
Gravitational Waves - Are all detectors finding the same gravitational waves?
I read that there have been approximately 90 recorded cases of gravitational waves. Have the 4 different gravitational wave detectors agreed on specific individual recordings or have all 90 cases been ...
- 649
0
votes
1
answer
52
views
Virtual Graviton Polarisations
Is it true that in canonically quantised gravity "non-traceless" and "non-transverse" gravitons are allowed to exist as virtual particles, whereas any graviton that corresponds to ...
- 523