# Simple geometric proof GR's GW's are impossible

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Q-reeus, Jul 7, 2016.

1. ### paddoboyValued Senior Member

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Whatever.
"Fact is the current aLIGO detections cannot offer sufficient data to distinguish between GR and G4v predictions. Plus further work needs to be done on chirp predictions for G4v."
Fact is that does in no way dispute GR GW's.

Last edited: Jul 11, 2016

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3. ### James RJust this guy, you know?Staff Member

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My apologies if a couple of legitimate on-topic posts got caught in the thread split. That was unintentional. About two-thirds of the posts to this thread were off-topic and moved.

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5. ### Q-reeusValued Senior Member

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Wrong inference as usual. From your #20:
Go read again #22 here. ONLY GW's HAVE BEEN CONFIRMED. WHICH VARIETY IS NOT YET DECIDED. Don't keep repeating nonsense.

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7. ### Q-reeusValued Senior Member

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OK fine. I'm surprised no such culling was done on the other thread also - which is actually worse in respect of de-railings and bun fights. But no - not suggesting it be done. It always leads to screwing up post # referencing.

8. ### paddoboyValued Senior Member

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Sorry, but the confirmation of GR GW's was also a confirmation of binary BH pairs.
I suggest you read up on reputable mainstream papers.

9. ### Q-reeusValued Senior Member

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The topic, in case you haven't noticed, is GW's, not BH's. And anyway, I could quote you sources admitting even BH's are not per se proven from aLIGO detection. In fact iirc that was done in another thread.

10. ### paddoboyValued Senior Member

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I'm speaking of GR type GW's as found in two occasions, and both as a result of binary BH pairs.
But you certainly are welcome to show me a source that disagrees with that, as long as it is reputable.

11. ### SchmelzerValued Senior Member

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[The context is in #165 in the other thread]

No. There is a whole class of metric pertubations which does not have curvature effects. These are metric pertubations which you can obtain also by a pertubation of the coordinates.

Try it out. Start with $\eta_{mn}$. Use a pertubation of the coordinates $x^{m'} = \delta_{mm'}x^{m} + \tilde{x}^{m'}(x)$ with some scalar waves $\tilde{x}^{m'}(x)$. Compute the modified metric, substract the original $\eta_{mn}$, and you have four independent metric pertubations which have no influence on the curvature, and, therefore, are invisible to any LIGO-like device. If you don't believe, compute the curvature tensor of the modified metric.
You see, they describe that other, alternative theories can have four more types of gravitational waves. These are these four waves described by the four functions $\tilde{x}^{m'}(x)$. In a theory with preferred coordinates, these waves define nontrivial physical solutions. Some non-covariant interaction term may create them as well as used in a detector to detect them.

In GR, this is impossible, because the theory is covariant. You can add these waves to any solution, and you obtain a solution which looks different in the functions $g_{mn}(x)$ but is equivalent, "the same" solution in other coordinates.

In GLET, which is not covariant, they exist. And are, at least in principle, observable. But not really - they interact only via the gravitatational field itself, a sort of ideal dark matter. Because the EEP holds in GLET too, a LIGO-like device is unable to see them too. You would have to construct some LIGO-like device hold together by purely gravitational forces - such a device could in principle observe them.

Last edited: Jul 11, 2016
12. ### Q-reeusValued Senior Member

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http://physicsworld.com/cws/article...g-gravitational-wave-signals-from-black-holes
Go down to 'Light rings' sub-heading. G4v, that Kip Thorne himself took seriously enough to commission a special template for aLIGO, also does not admit BH's. Nor Yilmaz gravity, whose MECO objects would in a binary merger event be likely to give a virtually identical chirp signal to BH's. Don't turn this into a thread derailing.

13. ### Q-reeusValued Senior Member

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If it involves perturbing coordinates I immediately smell coordinate artifacts. Also, without any 4-curvature surely they must be non-propagating i.e not wave solutions always having gradients.
Not worth the bother for several reasons. As per above, sounds like ghostly, non-propagating coordinate artifacts. Having no possible presence on the aLIGO etc. detector radar. That Living Reviews article plainly states that GR admits only TT waves (far field obviously). The assumption being such are generated by real matter sources having fluctuating multipole moments - beginning with quadrupole.

There is a general principle applicable to any type physical wave - EM, acoustic, GW, thermal, whatever. Any source must also be able to function as a detector - at least in principle. Your ghost waves (if actually waves not static/quasi-static entities) do not satisfy that criteria thus irrelevant to OP.

OP is about comparing what GR predicts for the case given - far field TT GW's owing to an oscillating linear mass quadrupole. Which nicely cuts to the base issue in a way obscured by the more popular orbiting binary treatments. I gave a reference for the field solutions. Which clearly confirms the illustrated local shear strains depicted in #1 have the correct orientations. The rest - impossibility of extending such purported local metric perturbations globally, follows immediately just by simple inspection of the axial symmetry involved.

You have ruminated on #19 as asked? So here's the deal. If you are indeed seriously open on the matter, take up my challenge in #8 PhysBang balked at. Well just this if you like - provide your own summary of what you think my central argument in #1 is. Not a caricature - a serious attempt to recapitulate the key logic. Made a very iffy start in #165 the other thread:
Now do it properly here. Once that's actually done, and I agree it is a fair summary, feel free to try and 'destroy it'.

14. ### Q-reeusValued Senior Member

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As a small aside, noticed someone at PhysicsForums started a thread, shortly after mine, with an eerily similar theme to it:
Aint it just amazing how much talking just words is done by the resident GR expert there. Awful. Owing to debating the binary case, the real problem is obscured as mentioned before.
Only the linear quadrupole axial symmetry allows the dilemma to clearly emerge. I do suspect though, going by the opening defensive wording, and illustrations used, the OP gent very likely payed a visit here prior to posting there.

15. ### paddoboyValued Senior Member

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Yep already been discussed with another....even more exotic objects, Gravastars, Wormholes, so how about applying some common sense and accept the overwhelmingly most likely...ie binary BH pairs that produced on two occasions gravitational waves so confirming to an even higher degree of certainty, GR, GW's and BH's
Again your following inferences sound like more conspiracy type talk.
We have literally a dozen or more papers confirming gravitational waves of the GR type, also confirming BH's.
http://arxiv.org/pdf/1607.00641v1.pdf
A dynamical gravitational wave source in a dense cluster

Abstract

Making use of a new N-body model to describe the evolution of a moderate-size globular cluster we investigate the characteristics of the population of black holes within such a cluster. This model reaches core-collapse and achieves a peak central density typical of the dense globular clusters of the Milky Way. Within this high-density environment we see direct confirmation of the merging of two stellar remnant black-holes in a dynamically-formed binary, a gravitational wave source. We describe how the formation, evolution and ultimate ejection/destruction of binary systems containing black holes impacts the evolution of the cluster core. Also, through comparison with previous models of lower density, we show that the period distribution of black hole binaries formed through dynamical interactions in this high-density model favours the production of gravitational wave sources. We confirm that the number of black holes remaining in a star cluster at late times and the characteristics of the binary black hole population depend on the nature of the star cluster, critically on the number density of stars and by extension the relaxation timescale.

https://arxiv.org/ftp/arxiv/papers/1602/1602.03837.pdf

Observation of Gravitational Waves from a Binary Black Hole Merger
Abstract:

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410þ160 −180 Mpc corresponding to a redshift z ¼ 0.09þ0.03 −0.04 . In the source frame, the initial black hole masses are 36þ5 −4M⊙ and 29þ4 −4M⊙, and the final black hole mass is 62þ4 −4M⊙, with 3.0þ0.5 −0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.
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"There are literally more than a couple of dozen papers throughout threads on GW's that all claim the same thing.
I certainly am not going to be swayed either to any doubt re GR type GW's, nor BH's by anyone on a science forum.
Again if you are serious about all this, practise the accepted scientific method and get it professionally peer reviewed by experts.

I don't derail threads thank you very much, but I also certainly won't be bullied.
So let that be the end of any attempted derailing by either of us, OK?

16. ### Q-reeusValued Senior Member

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Not interested in responding to such an omnibus assertion. Again - OP topic is self-(in)consistency of GR variety GW's. If you cannot contribute anything technically useful to the thread topic, which is obvious, be content to watch from the sidelines while possibly one or two here actually do so.
One day it may dawn on you that chronically accusing others of harboring 'conspiracy theories' is itself ironically a conspiracy theory mindset.
And I'm not interested in trying to sway the likes of yourself. So just relax and stay stalwartly unswayed.
Someone was trying to bully you? Well just be strong in yourself.

17. ### paddoboyValued Senior Member

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Ignoring the usual insults here's some more that may add to the confirmation of GR inspired GW's......

https://arxiv.org/pdf/1602.03841v2.pdf

Abstract:
The LIGO detection of GW150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. We carry out several investigations to determine whether GW150914 is consistent with a binary black-hole merger in general relativity. We find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (post-inspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. Furthermore, the data following the peak of GW150914 are consistent with the least-damped quasi-normal mode inferred from the mass and spin of the remnant black hole. By using waveform models that allow for parameterized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-Newtonian coefficients. We constrain the graviton Compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 1013 km. In conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity.

extract:
"The detection of GW150914 ushers in a new era in the field of experimental tests of GR. The first result of this era is that, within the limits set by our sensitivity, all the tests performed on GW150914 provided no evidence for disagreement with the predictions of GR".

18. ### paddoboyValued Senior Member

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Obviously you have also failed to sway anyone else also.

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19. ### SchmelzerValued Senior Member

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Feel free to name them "coordinate artefacts", this is close to what they are considered to be in GR spacetime ideology, where their existence in reality is denied. Once we cannot measure them, they do not exist.

As I said, try it out, learn how to compute the curvature, then compute the flat metric $\eta_{mn}$ in different curved coordinates, compute the curvature tensor in these different coordinates, and find out that it is really zero, even if the $g_{mn}(x,t)$ look very nontrivial, with quite arbitrary gradients, in such curved coordinates.

Look like non-propagating? LOL. Try it out, with coordinates $x^m \to x^m + f^m(x,t)$ with four functions $f^m(x,t)$ which look as much as propagating waves as you like. Simply use solutions of the standard wave equation $\square f^m(x,t)=0$ for them. Let's try:
$\eta_{mn} dx^m dx^n \to \eta_{mn} d(x^m+ f^m(x,t)) d(x^n+ f^n(x,t)) \approx \eta_{mn} (dx^m dx^n + \partial_k f^n dx^k dx^m + \partial_k f^m dx^k dx^n + \ldots) = (\eta_{mn} + h_{mn}(x,t)) dx^m dx^n .$
Now, if the $f^m(x,t)$ are harmonic waves, the $\partial_k f^m(x,t)$ as well as sums of them are such harmonic waves too. So, the $h_{mn}(x,t)$ too (approximately, which, as you have acknowledged, is not a problem).

And these are the four types of gravitational waves which in non-covariant theories are nontrivial gravitational fields, but in GR are valid but trivial fields. With zero curvature tensor (in all theories).

Oh, something new, you use some mainstream GR review as the ultimate authority, and refuse to check it, and to learn to understand why this is claimed. Once you accept it as an authority, why not also about the claim that in GR such waves exist?

And, just to clarify: The other waves cannot be nor created nor detected, but are admitted in valid solutions of GR as well.
Fine. This is what I have tried to explain you. In GR, they cannot be generated by anything, and cannot be detected by anything. That's why they can be ignored as irrelevant. And, with sufficient positivism, which rejects the very existence of unobservables, even as nonexistent. Or one can start name-calling them "coordinate artefacts", but even this does not change the formulas which describe them.

This in no way changes the fact that one can add them, and a GR solution remains, nonetheless, a GR solution. And in this sense, they are in no way forbidden. Only unobservable.

Unfortunately, I'm unable to interpret this text in a meaningful way. Same for #19 and the "challenge" #8.

But, nonetheless, the situation does not seem as hopeless as one may think. The issue we have started to discuss seems highly relevant in all the interpretations of #1, #8, #19 I have tried, and this issue is a sufficiently clear and simple one, so that there is a chance to find some agreement.

But to improve this process, a few questions:

1.) Given that $\eta_{mn}$ is a trivial vacuum solution of GR, do you agree that the metric computed above from this using the coordinate transformation $x^m \to x^m + f^m(x,t)$ is also a vacuum solution of GR?
2.) Do you agree that above have curvature tensor 0?
3.) Do you agree that the $h_{mn}(x,t)$ computed above look (approximately) like waves, once the $f^m(x,t)$ are solutions of the wave equation $\square f^m(x,t) = 0$, thus, like gravitational waves?
4.) Do you agree that these four types of gravitational waves are the four types of waves which, according to the Living Review article, are not present in GR?

20. ### PhysBangValued Senior Member

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You are using a toy system where you, in your assumptions, get rid of possible effects from gravitational waves. This might come out if you were to bother to provide a full argument that the waves have no effect rather than merely say that it is "obvious" that they have no effect.

Go back to your post, look for where you use the word "obvious" and try to replace that with an actual argument. Good luck.

21. ### Q-reeusValued Senior Member

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Thanks for candidly providing a perfect justification for completely ignoring such nonentities. I would certainly not waste any time plowing through tedious derivations, knowing in advance the above admitted basic defects. And imo strangely inconsistent of you to propose such 'ghost solutions' as worthy of consideration, while simultaneously a known contemptuous critic of better known GR solutions allowing wormholes and CTC's for instance. The latter sentiment I agree with as you know.
I sense a rather transparent strategy to weasel out of simply dealing with the vastly simpler case proposed in #1. Namely, I refuse to spend any time on such a pointless analysis - which as per above you acknowledge has no possible connection to real i.e. physically generated and detected GW's. That then means you will 'reciprocate' and refuse to do as I asked firstly - provide an honest, objective summary of my case as per #1.
Look, it would have been better to just straight out refuse. No need to concoct a flimsy quid pro quo precedent, intended to allow a 'graceful decline'. My invitation in #32 nevertheless remains open, in case you have a change of heart. Sigh. This is SF.

22. ### Q-reeusValued Senior Member

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Wrong interpretation. The 'toy' system or rather well known scenario of linear oscillator, illustrates that GR's claimed GW's cannot logically exist. Which is not at all denying possibility of other types - e.g. G4v, as I have repeatedly stated ad nauseam.
Well if the to me totally obvious symmetry constraint I pointed out in #1 doesn't gel with you, no point rehashing it now.
See above. Have a nice day.

23. ### James RJust this guy, you know?Staff Member

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Q-reeus:

I'm curious. What does LIGO detect, if not GR's claimed GWs? Or are its detections spurious?