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.

Filter by
Sorted by
Tagged with
1 vote
1 answer
51 views

Gravitational waves from metric perturbation

I have just been introduced to gravitational waves from metric perturbations and I have some questions about gauge symmetry and solutions in a given gauge. Consider a metric on the form $g_{\mu\nu} = \...
ICOR's user avatar
  • 69
0 votes
0 answers
50 views

Gravitational waves from any metric?

First, to be clear, I know practically nothing on gravitational waves and finding their solutions. The most I know confidently is that they are found by expanding the metric in a weak field expansion ...
MathZilla's user avatar
  • 602
11 votes
5 answers
1k views

How do gravitational waves carry energy when gravitational energy cannot be localised?

I have a very naive question, actually someone asked it and I can't answer. It simply asks that if gravitational energy cannot be localised (we cannot write a pure gravitational energy momentum tensor)...
damaihati's user avatar
  • 415
-1 votes
0 answers
59 views

How do we know the hypothetical graviton must be spin 2? What does that even mean? [duplicate]

How do we know the hypothetical graviton must have spin 2? What does that even mean? I can comprehend spin 1/2 fermions and spin 1 bosons, but I don't know what spin 2 would even apply. How was that ...
C Worthington's user avatar
0 votes
0 answers
51 views

Destructive interference of Gravitational Waves and the Conservation of Energy

Destructive interferences are interesting for a physics student, specifically when checking the Energy Conservation. In the case of destructive EM waves or String waves it is easy to understand where ...
TheFyziker's user avatar
14 votes
3 answers
2k views

How do physicists mathematically define gravitational waves?

When one first encounters gravitational waves in a standard GR lecture or a standard textbook like Carroll's "Spacetime and Geometry", they are often "defined" as follows: The ...
Moguntius's user avatar
  • 337
1 vote
1 answer
130 views

Can a single black hole emit gravitational waves and evaporate?

I have read this: Yes, single neutron stars can emit gravitational waves if they have sufficient asymmetries. For some background, an object symmetric about its axis of rotation does not produce ...
Árpád Szendrei's user avatar
1 vote
0 answers
32 views

Help to approximately invert Post Newtonian expression [closed]

Can anyone advice how to perform some sort of Taylor series approximation to compute the inverse of the following expression for $t(v)$ i.e. to obtain $v(t)$. Thanks! $$ t(v) = t_0 - \frac{5M}{256\eta ...
cyberface's user avatar
0 votes
0 answers
54 views

4-graviton vertex of which one is an emitting graviton

For a four graviton vertex function, suppose $h_{\alpha\beta}h_{\gamma\delta}h_{\varepsilon\zeta}h_{00}$, of which $h_{00}$ is the emitting graviton to infinity. Now if we associate four-momenta $p_1$,...
NovoGrav's user avatar
0 votes
1 answer
64 views

Orbital frequency of gravitational wave prior to merger [closed]

In the paper The basic physics of the binary black hole merger GW150914 Equation [A5] states that $$\dot \omega^3=\left(\frac{96}{5}\right)^3\frac{\omega^{11}}{c^{15}}\left(G\mathscr M\right)^5 \tag{...
Halcyon Mo's user avatar
1 vote
0 answers
30 views

Expression for the gravitational-wave energy-momentum tensor without choosing a gauge

While studying section 7.6 of Carroll's introduction to general relativity, I encountered difficulties deriving equation 7.165 for the gravitational-wave energy-momentum tensor. Unfortunately, I was ...
bruno henrique's user avatar
2 votes
0 answers
210 views

How Do Gravitons Follow Geodesics?

It is known that all particles follow a geodesic in spacetime. Presumably gravitons follow geodesics as well. However, how does one describe that mathematically? For the case of other particles it is ...
physics_2015's user avatar
4 votes
1 answer
187 views

Field equations for Maxwell and Einstein tensors in a weak field limit

I am following this paper here (arXiv here). What I want to do is derive equations ($2.7$) and ($2.8$) given in section $2$. While the authors include the higher order Euler Lagrangian terms in their ...
ShKol's user avatar
  • 302
0 votes
0 answers
84 views

Photons and gravitational wave

Both photons and gravitational disturbances travel at $c$. Given that a photon does cause a tiny stress in spacetime due to its energy, and the propagation of this stress is at the same velocity as ...
Rich's user avatar
  • 819
0 votes
1 answer
66 views

Can LISA observe BH beyond the observable universe?

Reading the paper "Astro2020 Science White Paper Where are the Intermediate Mass Black Holes?", and the plot in Fig.1, page 5, it seems LISA can see IMBH beyond 100 Gpc...Since the ...
riemannium's user avatar
  • 6,491
0 votes
1 answer
36 views

Observations of harmonics in gravitational wave experiments

In gravitational wave astronomy, we usually observe $f_{GW}=2f_K$ (gravitational wave frequency twice the orbital frequency from keplerian motion). However, we also know there should be harmonics with ...
riemannium's user avatar
  • 6,491
3 votes
1 answer
46 views

Gravitational waves and EOS in neutron stars

What is/are the gravitational wave observable/s that makes possible to measure the parameter/s of the equation of state of neutron stars?
riemannium's user avatar
  • 6,491
3 votes
2 answers
260 views

Merge of black holes with very different masses

Since surface area of the remnant black hole must be more that the sum of the binary surface then the maximum energy released via gravitational waves is $$ ΔE = [M_1 + M_2 – \sqrt{M_1^2 + M_2^2}]c^2 $$...
Vashu's user avatar
  • 629
2 votes
0 answers
61 views

Can I use gravitational wave to break electron's double slit interference?

Electrons will perturb spacetime. So in principle in a double slit experiment, I can detect the gravitational wave emitted by the electron by a super-super capable detector at very far away, and ...
user74750's user avatar
  • 159
2 votes
2 answers
96 views

Can Gravitational Waves Be Artificially Produced By An Electric Motor?

If gravitational waves are produced by two spinning black holes, is it possible to produce vacuum waves by mounting a giant dumbbell on a giant electric motor that can spin the dumbbell at a high ...
garmichaels's user avatar
0 votes
0 answers
35 views

Feedback control system in gravitational wave detectors

I am preparing for a seminar on ground-based gravitational wave detectors. One topic I have very little idea about is feedback control systems. I have a basic knowledge of it, but I need to read some ...
0 votes
1 answer
66 views

Can we use gravitational wave to detect which slit electron pass through?

Just in principle, in a double slit experiment, is it possible to use gravitational wave to determined which slit did an electron go through? I am honestly don't know, and it just a question that ...
Tensor's user avatar
  • 170
3 votes
1 answer
212 views

Detection of gravitational waves with rotating resonator

Attempts at detecting gravitational waves started with resonant-mass detectors. One gets some high Q mass and watches it's vibrations. When gravitational wave passes through the mass the latter gets ...
Vashu's user avatar
  • 629
15 votes
4 answers
5k views

Can gravitational waves do work?

I was reading about how a large amount of mass is lost as gravitational waves, X-ray radiation, and gamma radiation during a kilonova. I also read about the sticky bead analogy to better understand ...
user6760's user avatar
  • 13k
1 vote
0 answers
42 views

Thermal gravitational waves vs thermal radiation

A body at temperature $T$ has both an electromagnetic emission spectrum and a gravitational emission spectrum, are there any temperatures or conditions where the gravitational one could be comparable ...
Mauricio's user avatar
  • 5,436
0 votes
2 answers
78 views

Gravitational waves vs ULF Radio waves

During the recent merger of two Neutron stars the lead up to the merger was detected as gravitation waves. This was the merger of two spinning bodies that had very strong magnetic fields and they were ...
Michael Mcgarry's user avatar
2 votes
0 answers
46 views

Gravitational Wave Emission from Symmetrically Accelerating Systems

I've been exploring the concept of gravitational wave (G-wave) emission from symmetrically accelerating systems and have encountered a puzzling question. Standard sources typically state that ...
ElfredaCyania's user avatar
1 vote
2 answers
215 views

Does a linearly accelerating spherically symmetric body emit gravitational waves

According to Birkhoff's Theorem, any spherically symmetric body will not emit gravitational waves. I can understand this for an object that is contracting and expanding because from far away the ...
aP123's user avatar
  • 101
0 votes
1 answer
103 views

In terms of gravitational waves, what terms or components are actually embedded within $h_{\mu\nu}$?

In terms of gravitational waves: $$g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu}\text{ with } |h_{\mu\nu}|\ll 1$$ The components of $\eta_{\mu\nu}$ are $[-1,1,1,1]$ which expresses flat Minkowski spacetime. ...
Python House's user avatar
0 votes
1 answer
33 views

$v_{GW}$ near a star

The Einstein field equations may be written as $R_{\mu \nu }-{\tfrac {1}{2}}R\,g_{\mu \nu }={8\pi G}T_{\mu \nu }$. At a very large distance from massive bodies one can neglect $T_{\mu \nu }$ and ...
9herbert9's user avatar
  • 113
1 vote
1 answer
105 views

Conceptually, what does the amplitude term in the wave equation represent when describing a gravitational wave?

I'm trying to conceptually understand what the amplitude term in the wave equation for a gravitational term represents, which is depicted as $A = A_0\cos(\omega t-kx)$ where $A_0$ is the amplitude ...
Python House's user avatar
22 votes
4 answers
3k views

Does the gravitational field have a gravitational field?

I am currently reading electrodynamics from Feynman. When talking about the energy of the electromagnetic fields, he says that the location of the field energy could be known at least theoretically ...
veke's user avatar
  • 597
0 votes
1 answer
70 views

Can we correctly invoke energy conservation to explain why binary systems do collapse in GR?

I've learned that binary systems emits gravitational waves, so there is energy leaving the system in the form of waves and so the radius of the binary system must decrease as to maintain the ...
Acephalus's user avatar
  • 159
0 votes
0 answers
55 views

If gravity is fictitious force why we search for gravitons? [duplicate]

If gravity is fictitious force why we even search for gravitons? I mean, centrifugal or coriolis force don't have carriers, because these forces dont exist.
user707264's user avatar
3 votes
1 answer
211 views

Are gravitons radiated while the massive body turned making Earth orbit unstable?

When @anna v explained why the planetary model of the atom does not make sense in this post, she said the electron in an orbit is accelerating continuously and would thus radiate away its energy and ...
戴淯琮's user avatar
0 votes
0 answers
47 views

Can gravitational waves be compared with a sinking water phenomena?

Let's say we have some water in the sink and open the closure. The water starts to move towards it in a whirlpool-like manner. If we have a table tennis ball and leave it near the hole of the sink it ...
Krešimir Bradvica's user avatar
1 vote
0 answers
75 views

Correlations in the Hellings-Downs curve for the NANOGrav 15-year dataset

I'm trying to reproduce the Figure 1c from the paper "The NANOGrav 15-year Data Set: Evidence for a Gravitational-Wave Background". This graph corresponds to pulsar pair correlations of the ...
Just_A_Pangolin's user avatar
1 vote
1 answer
73 views

Reduced mass vs. Total mass in gravitational wave estimations

When people do back of the envelope calculations about GW physics, they always use a very abstract mass scale $M$ and I want to figure out the identity of said scale for different relevant magnitudes ...
P. C. Spaniel's user avatar
2 votes
1 answer
103 views

Can either of LISA, NanoGrav or LIGO measure the polarization of gravitational wave background (GWB)?

Polarization in GWB should carry as much important information as in CMB. However, I've done some superfluous literature research and found little discussion. Is there any planned project for ...
Bababeluma's user avatar
0 votes
1 answer
70 views

Multipole expansion, same charges

I know dipole is defined with 2 opposite charges. That's why in EM dipoles exist, while in gravity they do not. However, I view multipole expansion as a way to describe how the distribution of charges ...
Matteo's user avatar
  • 65
2 votes
0 answers
50 views

Can linear frame dragging cause gravitational dipole radiation?

I have just learned that linear frame dragging exists in General Relativity. I have also seen simulations where a periodically accelerated and decelerated mass causes a sort of gravitational dipole ...
ramiel46692's user avatar
1 vote
0 answers
105 views

Liénard-Wiechert potentials in General Relativity

In linearized gravity, we have. $$ \Box \bar{h}_{\mu \nu} = -\frac{16 \pi G}{c^4} T_{\mu \nu} $$ Solving the equationg for a point mass, with a trajectory $\mathbf r_0(t')$: $$ \rho(\mathbf r', t') = ...
Álvaro Rodrigo's user avatar
3 votes
4 answers
206 views

Would a gravitational wave shift where a laser pointer is pointing?

I know the effect would be incredibly small if there is one. If I were to point a laser pointer at the moon and a gravitational wave were to pass by perpendicularly to the laser would it shift the ...
Joe's user avatar
  • 1,346
4 votes
4 answers
518 views

Interpretation of gravitational waves

A wave has peaks and valleys. I can think of a sine wave as a wave with peaks and valleys. Now, if gravity is a wave, can we say that gravity would have peaks and valleys, with the valley becoming ...
Angela's user avatar
  • 993
1 vote
0 answers
43 views

Can energy of one field be converted to another?

From school we know examples of energy conversions: from electromagnetic to electric, from electric to heat, from heat to electromagnetic, etc. However, obviously this almost has nothing to do with ...
Stdugnd4ikbd's user avatar
0 votes
1 answer
41 views

Second mass moment for a specific rotating object

The polarization amplitude for gravitational waves can be written as a function of second mass moment. For example for a propagating wave along the $z$-direction, we have $$ h_+ = \dfrac{1}{r}\dfrac{G}...
Astrolabe's user avatar
  • 159
9 votes
2 answers
266 views

Is there partial gravitational shielding?

Gravitational waves carry energy. The sticky bead argument shows that this energy can be extracted: https://en.wikipedia.org/wiki/Sticky_bead_argument But Lee Smolin points out that "In ...
Manuel's user avatar
  • 498
1 vote
1 answer
49 views

Would there be any way to avoid gravitational waves emission in some orbital configurations?

In principle every object orbiting another (e.g. a planet revolving around a star) would emit gravitational waves, relaxing the orbit over time. ​ However, this would not happen if the orbits had a ...
vengaq's user avatar
  • 2,224
0 votes
1 answer
70 views

A question about bremsstrahlung radiation

It’s gravitational radiation, a sphere of mass expanding in a symmetrical manner will not give off gravitational waves. Does it work the same way with electromagnetism, will this result in an ...
blademan9999's user avatar
  • 2,870
2 votes
1 answer
64 views

Malus law for gravitational waves

What is the analogue of the Malus law for polarized electromagnetic waves to the cause of plus and cross polarized gravitational waves? Bonus: What if gravitational waves have further degrees of ...
riemannium's user avatar
  • 6,491

1
2 3 4 5
24