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Earlier this year, Carver Mead of CalTech published a paper which seems to be garnering a lot of attention:

http://arxiv.org/abs/1503.04866

http://www.npl.washington.edu/AV/altvw180.html

http://www.geekwire.com/2015/after-100-years-einsteins-general-relativity-faces-a-big-party-and-a-big-test/

I also watched the video of his talk at CalTech: https://www.youtube.com/watch?v=XdiG6ZPib3c

The Q&A at the end of this talk seemed to indicate that he may be misapplying GR equations for tasks for which they may not have been designed or for which they need proper manipulation.

The G4v theory claims, among other things, that it does away with the need for a Cosmological constant (which, based on the gravitational wave uses, I can understand) and also DOES AWAY with Dark Energy. It seems future LIGO experiments could provide supporting or refuting evidence for G4v.

My Question: How/why does this theory do away with the need for Dark Energy?

Does it invalidate prior calculations that the univerise is expanding at an accelerating rate? Or does it just describe the accelerating expansion without the need for the cosmological constant? If the latter, that still requires something accelerating the expansion, so I'm confused.

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    $\begingroup$ Essentially answered in: What are the differences between dark energy and a cosmological constant?; Cosmological constant is one possible model of dark energy, so whatever "does away" with the constant also "does away" with dark energy since we have no reason to believe it is varying. $\endgroup$
    – ACuriousMind ♦
    Nov 26, 2015 at 0:42
  • $\begingroup$ My understanding is that observational data seems to strongly suggest a universe w/accelrating expansion. Can't the acceleration be represented in terms of a positive cosmological constant--merely the rate of the expansion? If the universe is not expanding, the constant is zero. If it is contracting, the constant is negative, correct? Isn't Dark Energy, on the other hand, just one explanatory model causing this expansion? If one does away with a positive cosmological constant, doesn't that mean it also does away with an expanding universe altogether--which seems to go against observations? $\endgroup$
    – Brad Cooper - Purpose Nation
    Nov 26, 2015 at 6:24
  • $\begingroup$ John Cramer, the source of one of the cited articles above, tells me, "Brad, Carver Mead says G4v is not disproved, but calculations needed to see if it can do as well as GR in fitting the LIGO data. The problem: main differences b/w G4v & GR predictions are in polarization & Hanford & Livingston, b/c arms are almost parallel & are relatively insensitive to polarization. A LIGO speaker at UW last week said that may have to wait until VIRGO in Italy comes online (soon, but need to see an event after it does) to have the polarization sensitivity to falsify 1 of the predictions. Regards, John" $\endgroup$
    – Brad Cooper - Purpose Nation
    Mar 6, 2016 at 17:12
  • $\begingroup$ I have futher correspondence from the group leader of the CalTech LIGO team, Alan Weinstein (thanks, Alan!): "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)... $\endgroup$
    – Brad Cooper - Purpose Nation
    Apr 17, 2016 at 3:30
  • $\begingroup$ "...predictions from G4v are not yet available; Carver is working hard on it. 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, 2016 at 3:30

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Carver Mead's version of the G4V theory includes a 2nd order term in the equation for inertial momentum which is proportional to the integral of the velocity of all relativistic energy in the universe divided by its distance from the body of interest. The term is expressed as being proportional to the inertial vector potential. It provides a description of a mechanism which, if found to exist, would embody Mach's principle. Because of its sign, it would also tend to explain the currently unexplained expansion observed in macroscopic regions of the universe which is currently ascribed to "dark energy." It contains no "fudge factor" analogous to the intermittently-hypothesized cosmological constant. The LIGO experiment should imminently provide data of sufficient accuracy to differentiate between G4V and GR, which is cause for excitement. For an initial foothold, see: https://youtu.be/XdiG6ZPib3c

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  • $\begingroup$ Thanks much, @godot. You and herb terpening are tied for the best answer here. I have been searching for it, but I see no mention of the LIGO discovery either supporting or refuting GR or G4V. Anyone see anything about this? $\endgroup$
    – Brad Cooper - Purpose Nation
    Feb 15, 2016 at 19:06
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John G. Cramer discussed G4V in a recent Analog Alternate View Column (Mar. 2016), and how Advanced LIGO data could possibly falsify G4V, General Relativity or even both of them (Their predicted gravity wave signatures signatures differ.)

Cramer also stated that there would be no dark energy since G4v explains distant receding Type IIa supernova dimming as partially due to relativistic beaming leaving no need for a cosmological constant.

In other words, the accelerated expansion is an illusion because more distant Type IIa supernovas appear dimmer than previously predicted if G4V is correct.

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  • $\begingroup$ Thanks much, @Herb_Terpening. I did also post the John Cramer link in my original question (i guess it took a while to appear in print). You and godot are tied for the best answer here. I have been searching for it, but I see no mention of the LIGO discovery either supporting or refuting GR or G4V. Anyone see anything about this? $\endgroup$
    – Brad Cooper - Purpose Nation
    Feb 15, 2016 at 19:07
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    $\begingroup$ @PurposeNation : in the near question G4v Gravitational Wave vs General Relativity vs LIGO Observation , James Bowery reports the Ligo statement on GR vs G4v $\endgroup$
    – user46925
    Feb 17, 2016 at 8:09
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    $\begingroup$ @igael: thanks, guess he could have done it here, but then that wouldn't have gotten him points for asking a "new" question. ha. $\endgroup$
    – Brad Cooper - Purpose Nation
    Feb 19, 2016 at 0:41
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Gravity is assumed to be attractive only. the cosmoconst/dark energy is Assumed to exist in order to explain the observed accelerating expansion.

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    $\begingroup$ This does not answer OP's question. $\endgroup$
    – DilithiumMatrix
    Nov 27, 2015 at 5:30
  • $\begingroup$ It does its about conservation of zero curvature as a fundamental property $\endgroup$
    – Brian Strandberg
    Nov 27, 2015 at 5:32

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