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.

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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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Consequences of a stable geon

What would be the consequences be of a stable geon? What similiarity, if any, would it have to a naked singularity? What would a stable geon potentially look like, and what would the immediate ...
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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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Elastic modulii of spacetime

With the confirmation of gravitational waves, it got me thinking -- is there an effective elastic modulus for spacetime? Because the wave propagates, it should be possible I would think to derive a ...
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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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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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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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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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light gravitational wave interaction

What happens when light photos and gravitation waves collide? Like can the photon "surf" on the gravitational wave and change direction, wavelength, velocity?
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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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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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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 here:...
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Could mesuring particles in double slit experiment with gravitational waves work?

From my basic knowledge of quantum physics I know that what makes the double slit experiment hard to understand is the mesurement part. Once you mesure a particle you become part of the wave function ...
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Gravitational Waves, Dipole Radiations and Momentum

I am trying to understand Gravitational Waves and and going through MTW's book. They state that there can be no dipole radiation because of the conservation of momentum but gravitational waves also ...
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Are gravitons possible in 2+1 spacetime dimensions?

Spin-1 massless particles are transverse waves, so they need at least three space-time dimensions to exists. As for gravitons, I think they are still not possible in three dimensions, and to reveal ...
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Can two magnetars collide?

Kilonova occurs when neutron stars inspiral and smash into each other releasing gigantic gravitational waves and materials, what about when their subsets were to collide? Would the powerful magnetic ...
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Gravitational wave due to photon?

Does photons create gravitational waves as they travel through space? I know that when matter particle moves, they create gravitational waves but does that same thing applies to photons as well and if ...
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Could we detect gravitational waves emitted outside particle horizon?

As we can see from a normal spacetime diagram like below, there's an overlap of the area within the event horizon and the area outside the particle horizon. Could we detect gravitational waves from ...
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What does determine the frequency of gravitational waves caused by inflation?

It is theorized that during inflation gravitational waves are produced. See this article by Guzzetti, Bartolo, Liguori, and Matarrese (Cornell University). Or this one by Liu, Guo, Cai, and Shiu (...
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How does Zerilli come up with this solution?

I am studying the paper "Gravitational field of a particle falling in a Scharzschild geometry analyzed in tensor harmonics" by Zerilli. The author calculates the gravitational radiation ...
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LISA acceleration noise formula

In the Laser Interferometer Space Antenna (LISA) mission proposal document, section 4.2 (page 17) there is a formula for the test mass acceleration noise level: \begin{equation} S_a^{1/2}\leq 3\cdot ...
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How close can two black holes in a binary system get, before they merge?

Sorry if this question is too elementary, as is my level, but I'm wondering how close two supermassive black holes can get and should the Keplerian rotational frequency at that point equal to the ...
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General Relativity: Non-static stable solution of an infinite multi-body system

If you take Einsteins field equation with a homogenous (and isotropic) mass density, no pressure, no cosmological constant and a flat, non-expanding spacetime, the result is a collapsing space-time (...
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Energy density of gravitational waves

If the mass is small enough, we can approximate to the GEM (gravitoelectromagentism). In this apporximation, we can calculate the energy density of gravitational field, such as $u_g=-\frac{g^2}{8\pi G}...
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Are gravitational waves absorbed or scattered by matter?

Is there an equivalent non vacuum medium of propagation for GW's? Can GW's be absorved or damped? Reflected? Can we perform a double slit experiment on GW's?
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What factors affect the strength of gravitational fields, to what proportion and magnitude?

I have been doing a physics depth study on the topic of "how gravitational waves affect the phase shift of light (in a vacuum)" and have found it difficult to find a source, at least one I ...
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Increasing observable universe size using primordial gravitational vaves

Using photon decoupling, the size of the observable universe is generally evaluated as being around 45 billion light-years at current time. When, and if we can detect primordial gravitational ...
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The variation of the flux of the linkage for the asymptotically flat spacetime

The concept of the linkage for the asymptotically flat spacetime is defined and dicussed in this paper by Geroch and Winicour. This is a nice paper, but I came across one problem. The linkage is an ...
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Momentum in Gravitational Waves - Maggiore's explanation

In Maggiore's book on Gravitational Waves, he derives the energy-momentum tensor $t_{\mu\nu}$ associated with a gravitational wave. From this, he gives in equation (1.161) that the momentum (in the $k$...
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How to get this metric tensor perturbation equation? (Gravitational wave)

(I need some time to come back to re-edit this post) LHS of equation 7.37 is gauge invariant The Twisted H symbol is comoving hubble parameter, the h_ij is metric perturbation, I do not know how to ...
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What's the shortest "safe" distance from a neutron star merger?

Take GW170817 for example, the first neutron star collision picked up by LIGO. Given how much data we got from that event, can anyone figure out what the "blast radius" is, and how far away from the ...
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Gravitons from linearized gravity

Linearizing gravity as follows: $$ g_{\mu\nu}=\eta_{\mu\nu}+h_{\mu\nu} $$ Up to this point, everything is a 4x4 matrice. How does one eventually recover a spin-2 particle which, according to https:/...
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Tianqin project vs LISA

How does Tianqin space-based gravitational wave detector compare to LISA? Will it be able to detect gravitational waves from e.g. inflation (considering possible upgrades)?
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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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Direct observation of Gravitational Waves via increased resolution

First, congrats to the event horizon team for the first photograph of a black hole. Not to downplay the significance of the photo, but it is a bit blurry. Still, it got me thinking. One might expect ...
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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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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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Hulse-Taylor binary data gap in the nineties

I was wondering what is the reason there are no data points in the famous Hulse-Taylor plot of the period decay in the 1990s. Does anyone know why no one collected data during this period?
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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 ...