16
$\begingroup$

CalTech emeritus professor Carver Mead produced an alternative prediction, to General Relativity, for gravitation wave observation which he published last year in anticipation of LIGO observations.

The "Opposite GR Prediction":

G4V's Opposing Prediction to GR

Moreover, the LIGO experiment is designed in such a way that it very well could discriminate between GR's and G4v's predictions.

enter image description here

The LIGO observation of gravitional waves have now been made. Were they of sufficient quality to discriminate between these (and possibly other) predictions, as the LIGO scientists had designed the experiment?

Gravitational Waves in G4v

Carver Mead (Submitted on 16 Mar 2015)

Gravitational coupling of the propagation four-vectors of matter wave functions is formulated in flat space-time. Coupling at the momentum level rather than at the "force-law" level greatly simplifies many calculations. This locally Lorentz-invariant approach (G4v) treats electromagnetic and gravitational coupling on an equal footing. Classical mechanics emerges from the incoherent aggregation of matter wave functions. The theory reproduces, to first order beyond Newton, the standard GR results for Gravity-Probe B, deflection of light by massive bodies, precession of orbits, gravitational red shift, and total gravitational-wave energy radiated by a circular binary system. Its predictions of total radiated energy from highly eccentric Kepler systems are slightly larger than those of similar GR treatments. G4v predictions differ markedly from those of GR for the gravitational-wave radiation patterns from rotating massive systems, and for the LIGO antenna pattern. The predicted antenna patterns have been shown to be highly distinguishable in the case of continuous gravitational-wave sources, and should therefore be testable as data from Advanced LIGO becomes available over the next few years.

Improve this question
$\endgroup$
10
  • $\begingroup$ Do you have any cites? I was able to find only one such comment regarding G4V. : Sonhouse4.2 / 5 (10) Feb 11, 2016 I guess the G4V theory of gravity waves by Carver Mead is shot down then. Read more at: phys.org/news/2016-02-gravitational-years-einstein.html#jCp $\endgroup$
    – James Bowery
    Feb 12 '16 at 18:29
  • 2
    $\begingroup$ From an anonymous respondent: "the two aLIGO interferometers have somewhat different orientations, with the x-arm at Hanford making an angle of 36 degrees with North and the x-arm at Livingston making an angle of 109.72 degrees with North. This creates a difference in sensitivity to the polarizations of the gravitational waves, and GR and G4v make very different predictions about polarization at emission and detector polarization sensitivity. A careful analysis of this effect needs to be investigated." $\endgroup$
    – James Bowery
    Feb 13 '16 at 22:10
  • 1
    $\begingroup$ From the LIGO team's paper Tests of general relativity with GW150914 "No constraint on non-GR polarization states. GR predicts the existence of two transverse traceless tensor polarizations for GWs. More general metric theories of gravitation allow for up to four additional polarization states: a transverse scalar mode and up to three longitudinal modes [13, 95]. Because of the similar orientations of the Hanford and Livingston LIGO instruments, our data cannot exclude the presence of non-GR polarization states in GW150914." They have not, yet, discriminated between GR and G4v. $\endgroup$
    – James Bowery
    Feb 16 '16 at 15:17
  • $\begingroup$ I suppose it's reasonable to call that an answer based on the phrase "our data" as opposed to "this analysis of our data". Before I mark this as answered I'd like a more authoritative corroboration of that interpretation of the passage. $\endgroup$
    – James Bowery
    Feb 16 '16 at 17:48
  • 1
    $\begingroup$ It does according to John G. Cramer. Do you have reason to believe he's wrong? npl.washington.edu/AV/altvw180.html Also, do you believe Kip Thorne was wasting his time, and taxpayer money, when he talked to Carver Mead about modifying aLIGO's design to be able to discriminate between transverse and longitudinal waves based on A4v's requirements? $\endgroup$
    – James Bowery
    Mar 3 '16 at 23:37
8
+50
$\begingroup$

John Cramer, the source of one of the cited articles above, tells me:

"Dear Brad,

Carver Mead says that G4v is not disproved, but calculations are needed to see if it can do as well as GR in fitting the aLIGO data. The problem is that the main differences between G4v and GR predictions are in the polarization behavior, and Hanford and Livingston, because their arms are almost parallel, are relatively insensitive to polarization. A LIGO colloquium speaker at UW last week said that they may have to wait until VIRGO in Italy comes on line (real soon now, but they need to see an event after it does) to have the polarization sensitivity to falsify one of the predictions.

Regards, John Cramer"

So, indeed, it seems the parallel nature of the LIGO arms is making it difficult to make a determination. VIRGO was mentioned, but I also do wonder if eLISA will provide any insights on this question:

https://www.elisascience.org/

Improve this answer
$\endgroup$
5
  • 1
    $\begingroup$ I have futher correspondence from the group leader of the CalTech LIGO team, Alan Weinstein (thanks, Alan!): $\endgroup$
    – Brad Cooper - Purpose Nation
    Apr 17 '16 at 3:19
  • 1
    $\begingroup$ "Short answer: discovery neither supports nor refutes G4V. Tests have not yet been done. For now, we have ONLY tested the data from GW150914 vs. predictions of GR (arxiv.org/abs/1602.03841 ). Have NOT compared the data to any other theory. The # of alt. theories is large, and will require a lot of effort to cover them (indeed, it was a lot of effort to compare vs. the extremely well-studied predictions from GR). Predictions from G4v are not yet available; Carver is working hard on it... $\endgroup$
    – Brad Cooper - Purpose Nation
    Apr 17 '16 at 3:27
  • 1
    $\begingroup$ "...Expect him to produce waveform predictions from the inspiral phase of the waveform soon. The post-inspiral phase(s) are more difficult to model (indeed, in GR, it requires supercomputer computations representing the work of dozens of researchers over decades). When predictions from G4v are available, we are eager to compare them against the data, in close consultation w/Carver. Hopefully, soon!" $\endgroup$
    – Brad Cooper - Purpose Nation
    Apr 17 '16 at 3:27
  • 1
    $\begingroup$ Update from npl.washington.edu/AV/altvw193.html: "The result of this comparison is a decided victory for Einstein's general relativity." $\endgroup$
    – Milton Silva
    Jun 24 '18 at 11:22
  • $\begingroup$ Has Carver Mead thrown in the towel? $\endgroup$
    – James Bowery
    Dec 6 '18 at 4:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.