Questions tagged [gravitational-waves]

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How much energy does the Earth absorb when a gravitational wave passes through it?

I understand that gravitational waves pass quite freely through massive bodies. Quoting http://www.ligo.org/science/GW-Potential.php: Gravitational waves will change astronomy because the universe ...
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445 views

Will a black hole cause scattering of a gravitational wave?

In my GR textbook, it states that gravitational waves can undergo interference but not scattering. I am just starting the chapter on linearised gravity concepts (weak field approximation) and my ...
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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 ...
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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 \gamma_{\mu\...
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Can one distinguish between near and far field for gravitational radiation?

For electromagnetic radiation one usually distinguishes between near and far field. The wave equation for the far field are based on Maxwell equations for the vacuum and predict that the radiated ...
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282 views

Degrees of freedom in General Relativity

A way one counts degrees of freedom(i.e. independent entries of the metric tensor ) in General Relativity is this: one goes to the linearized version, vacuum solution, and he sees that there are two ...
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306 views

Can gravitational waves produce “sonic boom”?

I've heard that a fast moving object such as a jet plane traveling much faster than speed of sound can produce shockwaves which is also known as sonic boom, also Cherenkov radiation is produce by ...
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70 views

Could two atomic clocks really be used to detect gravitational waves from a distant source? If so, how?

Three articles report on the recent paper in Phys Rev. D: Flanagan, Éanna É. et al. 2019 Persistent gravitational wave observables: General framework (also ArXiv): Phys.org: Gravitational waves leave ...
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59 views

What is the upper bound for the index of refraction of space?

It seems that gravitational waves and gamma waves travail at about the same speed, arriving within seconds of each other over distances in the ranges of $10^6$LY. Naively, I would assume this caps the ...
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76 views

Neutron star merger: large scale dynamics

Yesterday was announced the first detection of a neutron star merger via gravitational and electromagnetic waves. On the announcement one of the speakers is showing a simulation of the dynamics of ...
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179 views

Does a binary system really emit gravitational waves?

In this essay from Petkov, it is stated on page 13 that when the stars follow their orbits in the binary system, they do not emit gravitational waves since they move by inertia according to general ...
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Interaction with Gravitational Radiation

I have a question about hypothetical gravitational radiation. To put it simply, is there any sort of material or field or other force which can interact with it? I'm thinking about lenses and mirrors ...
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86 views

Characteristics of wavepackets

I've been learning about wave packets and group velocities recently and had a question. Using simple trigonometric identies, we can show that the super position of two traveling waves with frequency-...
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78 views

Can gravitational waves observed far from a black hole tell us anything about the multipole moments of a dynamical horizon?

In a paper by Ashtekar et al in 2013 on the approach to the final state to a stationary black hole they study the evolution of the multipole moments of dynamical horizons, which relax away (except for ...
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160 views

Non-locality of gravitational energy

Gravitational energy is non-local which is essentially because of the equivalence principle. The equivalence principle says that you can always transform your frame so that you feel like in a ...
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116 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 ...
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154 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 ...
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189 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 ...
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72 views

Radiation Pressure Noise in Gravitational Wave Detection

I am trying to work out where equation 9 comes from in Martynov et al. (2016), who discuss the radiation pressure noise in the LIGO detector. $$L(f) = \frac{2}{cM\pi^2 f^2} \left(h \nu G_{-} P_{\rm ...
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Gauge invariance of pseudo stress-energy tensor of gravitational waves

The pseudo stress-energy tensor of gravitational waves is given by $$T_{\mu\nu}^{(\mathrm{G}\mathrm{W})} = \frac{1}{32\pi}\left\langle \partial_{\mu} \bar{h}_{\alpha\beta} \partial_{\nu}\bar{h}^{\...
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36 views

Approximating a linearized gravitational wave expression

This is in the context of gauge fixing condition for obtaining linearized gravitational waves. $g_{ab}=\eta_{ab}+h_{ab}$ and $h_{ab}$ is the small perturbation that stands for the gravitational wave. ...
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144 views

Effective stress-energy tensor for a gravitational wave, compared to static semi-Newtonian case

There is a calculation that I had been thinking for a long time of working out to my own satisfaction, both because of its intrinsic importance and because it seemed like it would be fun. This was to ...
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Why gravitational waves are not part of thermal phenomena?

Electromagnetic waves are part of thermal phenomena in the form of thermal radiations. But why gravitational waves do not show up as a thermal phenomenon, for example, why gravitational waves do not (...
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Redshift z=40 and gravitational waves

Why z=40 is the critical value of the redshift (more or less) to decide find out primordial gravitational waves around it? I have read that is related to the following issue: black hole mergers ...
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Can gravitational waves be absorbed near a quasar?

As the Quasar Wikipedia article explains, a quasar is powered by gas falling into a supermassive black hole at the center of a galaxy. The Luminous infrared galaxy article says that, in extreme cases, ...
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Inflationary model that predicts both gravitational waves and isocurvature perturbations

I 'm searching for inflationary models that predict both gravitational waves and isocurvature (isothermal) perturbations. If I understood well, de Sitter inflation predicts only curvature (adiabatic)...
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Help with the solution to the linearized wave equation known as Retarded Integral

I need some little help here I'm reading about gravitational waves and particularly about gravitational waves described by the linearized non-homogeneus Einstein's equations \begin{equation} \left( -...
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138 views

General Relativity and spin/helicity two massless particle

I usually read that GR can be thought of as the unique theory of a massless spin-2 particle (I think that this is the graviton). I know that GR is the unique theory that has: diffeomorphism ...
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187 views

Is there any primordial gravitational wave(form) that could explain dark energy?

First, I asked myself the question: Is there any gravitational waveform, however fantastical, that could explain dark energy. I suppose for a ubiquitous gravitational wave to be an explanation for ...
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125 views

Can Bose-Einstein Condensates reflect gravitational waves?

This is a question based on the paper by Raymond Chiao in 2002 where it is stated: One of the conceptual tensions between quantum mechanics (QM) and general relativity (GR) arises from the clash ...
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62 views

Do gravitational vawes deplete energy even if there's nothing they can affect?

I've read multiple times that one of consequences of gravitational waves being a thing is, that they make any orbit unstable. As long as the two or bodies orbit around each other, they create ...
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208 views

LIGO detection statistic, SNR formula

According to B. P. Abbott paper published in Physical Review Letters, "Observation of Gravitational Waves from a Binary Black Hole Merger" http://journals.aps.org/prl/abstract/10.1103/PhysRevLett....
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Have gravitational waves any effect on the electromagnetic waves in interferometers?

I am not into general relativity, but the explanation of how an interferometric gravitational antenna works is generally pretty basic. In the recently published paper announcing the detection of ...
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Momentum transfer from gravitational wave

There has been some discussion here of the magnitude of the tidal distortion caused by a wave of the type reported on Feb. 11 2015, with the conclusion being that a tidal (distortion) effect ...
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137 views

How do gravitational waves and black holes interact?

Following the first detection of gravitational waves yesterday (11 Feb. 2016) by LIGO, I have a couple of questions about how gravitational waves and black holes interact. Assume that there is a ...
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283 views

If gravitational field has negative energy density, how does gravitational radiation carry positive energy?

The following question uses the analogy between EM (electromagnetism) and GM (gravitomagnetism). In order to force two like electric charges nearby, some work has to be done. This implies that the ...
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What happens in theory if we focus gravitational waves into a point?

https://www.youtube.com/watch?v=iWKFPTgkpXo Basically inspired by this video and its comparison with wormholes. While many other questions on the site have already covered the weak strength of ...
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Gravitational $N$-body mergers?

Beyond binary systems and its mergers, have numerical relativity groups computed an approximation to $N$-body GW signals/waveforms or is that a hard unsolved task?
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If I were to shake a black hole, does it grow bigger?

Imagine I were to shake a black hole rigorously, does it grow bigger? I think it will simply radiate all the kinetic energy gained from the shaking as gravitational wave right? In the normal case, if ...
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Could a black hole and a white hole cause gravitational waves, if orbiting one another?

I have been puzzled by an idea that I came across while reading about white holes. But I've only just started learning about white holes, so my knowledge is severely limited. It seems I also can't ...
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Bound on large extra dimensions using gravitational waves

Are there proposed observations using gravitational waves which put a bound on the size of large extra dimensions (say in the context of ADD model)? The claim in the ADD paper is that you cannot ...
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Would a free falling object hits by gravitational wave accelerate towards the source however briefly?

Gravity is acceleration so I would imagine an object that is in free fall to experience a force when hits by the gravitational wave but in which direction is my question?
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Is there a way to describe gravitational waves and time-dependent gravitation without tensors?

I have been reading about gravitational waves, and they fascinate me. However I struggle to follow the mathematics behind it, because they are described using tensors, index gymnastics, et cetera. Is ...
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Slowdown of gravitational waves measurement

As far as I can understand, the gravitational waves also slow down on interaction with matter similar to light rays. I am trying to understand if we can measure this? Suppose we put two detectors on ...
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Pendulum usage in gravitational wave detectors

I've read that pendulums are (or were) used to calibrate the distance between the mirrors in a gravitational wave detector. In principle pendulums are supposed to be moving in just one plane no matter ...
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Has anyone ever tried to derive gravitoelectromagnetic waves equation?

Has anyone ever tried to derive gravitoelectromagnetic waves equation? As we know, there is Maxwell-like equation in gravity. Has anyone here ever formulated gravito electromagnetic waves equation ...
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About the “Spindown problem”

I am studying General Relativity, following the lessons too, and some days ago the professor mentioned, in a very "fancy and quick" way a thing called "the spindown problems". For what I understood, ...
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How do the LIGO facilities know that their gravitational waves have not been distorted by other events and other waves?

Several black hole collisions have been detected. How do they determine if the gravitational waves have been strengthened or weakened by interaction with other event waves?
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Does special relativity apply to gravity wells?

If the gravity well of a non-rotating heavy object is in roughly the same inertial frame as an observer, its spacetime geometry (as measured e.g. by photon lensing) will present as spherically ...
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Gravitational waves formula

Gravitational waves are transmitted in environment in form of waves. Is there any formula for their energy of these waves?