A relativistic generalization of Milgrom's MOND theory that explains dark matter phenomena as a gravity modification has been fit to the cosmic microwave background (CMB) power spectrum.
Conventional wisdom has long argued that only dark matter particle theories could explain, although I had long suspected that if MOND could reproduce dark matter phenomena at galactic scales, that a generalization of it could so so at cosmological scales.
This is a huge boost to the gravity modification side in the "dark matter v. MOND" wars within astrophysics and cosmology.
Constantinos Skordis and Tom Złosnik. . . . have shown a version of a relativistic MOND theory (which they call RelMOND) . . . does fit the CMB power spectrum. Here is the plot from their paper:
Via Triton Station.
The paper and its abstract are:
We propose a relativistic gravitational theory leading to Modified Newtonian Dynamics, a paradigm that explains the observed universal acceleration and associated phenomenology in galaxies. We discuss phenomenological requirements leading to its construction and demonstrate its agreement with the observed Cosmic Microwave Background and matter power spectra on linear cosmological scales. We show that its action expanded to 2nd order is free of ghost instabilities and discuss its possible embedding in a more fundamental theory.
Constantinos Skordis, Tom Złosnik, "A new relativistic theory for Modified Newtonian Dynamics" arXiv (June 30, 2020).
7 comments:
Hi Andrew,
Does their theory preserve Lorentz invariance? (before I go to the trouble of reading it.)
Cheers,
Guy
Seems like big news! But as "Alexandre" points out in comments at Stacy McGaugh's blog, this is the kind of modified gravity that has extra fields (scalar and vector in this case), and so there will be new quanta as well, i.e. new particles. So it could still be counted as a "bosonic dark matter" theory, albeit one which produces that third acoustic peak in a different way. Btw the fit seems very good.
@Mitchell,
how does this proposal differ from GR + Higgs a gravity theory with a scalar field, except Higgs has been shown to exist via LHC?
or to put it another way, if this paper results are valid then could the Higgs boson and GR create the third peak in the CMB?
"if this paper results are valid then could the Higgs boson and GR create the third peak in the CMB?"
No.
Hum...
"The resulting action is that of the Gauged Ghost Condensate (GCC) which has been proposed [81] as a healthy gauge-invariant theory of spontaneous
Lorentz violation." So not Lorentz invariant, but not divergent. Now I have to go off and read about Ghost Condensate. I think it's a required ingredient for high level elixirs.
Cheers,
Guy
From the Triton Station Comments:
"By my analysis, MOND seems to over-predict the vertical force. The *shape* is right – the variation of K(z) is precisely predicted, but with an offset.
Despite all the existing work, I think it remains early days for this problem, in terms of both the data and its analysis. Many qualitative predictions of MOND are apparent in the data, but quantitatively the vertical force doesn’t seem to match up (at this ~30% level) with the radial force."
Discussed at https://iopscience.iop.org/article/10.3847/0004-637X/816/1/42
Neo: their scalar needs to work differently to the Higgs, both in its intrinsic properties and in how it interacts with the other fields. For more, see here.
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