Deur's approach to gravity, emphasizing gravitational field self-interactions in weak fields, that are generally neglected on the assumption that they are negligible in aggregate effect, is used to explain the Cosmic Microwave Background power spectrum which is the crowing achievement of the LambdaCDM model.
Figure 2 from the paper
Field self-interactions are at the origin of the non-linearities inherent to General Relativity. We study their effects on the Cosmic Microwave Background anisotropies. We find that they can reduce or alleviate the need for dark matter and dark energy in the description of the Cosmic Microwave Background power spectrum.
A. Deur, "Effect of the field self-interaction of General Relativity on the Cosmic Microwave Background Anisotropies"
arXiv:2203.02350 (March 4, 2022).
The introduction in the body text explains:
The power spectrum of the Cosmic Microwave Background (CMB) anisotropies is a leading evidence for the existence of the dark components of the universe. This owes to the severely constraining precision of the observational data and to the concordance within the dark energy-cold dark matter model (Λ-CDM, the standard model of cosmology) of the energy and matter densities obtained from the CMB with those derived from other observations, e.g. supernovae at large redshift z. Despite the success of Λ-CDM, the absence of direct or indirect detection of dark matter particles is worrisome since searches have nearly exhausted the parameter space where candidates could reside. In addition, the straightforward extensions of particle physics’ Standard Model, e.g. minimal SUSY, that provided promising dark matter candidates are essentially ruled out.
Λ-CDM also displays tensions with cosmological observations, e.g. it overestimates the number of dwarf galaxies and globular clusters or has no easy explanation for the tight correlations found between galactic dynamical quantities and the supposedly sub-dominant baryonic matter, e.g. the Tully-Fisher or McGaugh et al. relations.
These worries are remotivating the exploration of alternatives to dark matter and possibly dark energy. To be as compelling as Λ-CDM, such alternatives must explain the observations suggestive of dark matter/energy consistently and economically (viz without introducing many parameters and fields). Among such observations, the CMB power spectrum is arguably the most prominent.
Here we study whether the self-interaction (SI) of gravitational fields, a defining property of General Relativity (GR), may allow us to describe the CMB power spectrum without introducing dark components, or modifying the known laws of nature. GR’s SI already explains other key observations involving dark matter/energy: flat galactic rotation curves, large-z supernova luminosities, large structure formation, and internal dynamics of galaxy clusters, including the Bullet Cluster. It also explains the Tully-Fisher and McGaugh et al. relations. First, we recall the origin of GR’s SI and discuss when it becomes important as well as its overall effects.
Some other graphs from the conclusion to the paper pertinent to cosmology are below:
Hi Andrew, Is there any way to find out if cosmologists are taking Deur's theory at all seriously? Cheers,
ReplyDeleteGuy
There are few citations to him (on points that aren't particularly deep), although he now has a pretty decent number of peer reviewed publications, several papers with co-authors, and some citations that are not co-citations including one recent one that called a paper he wrong on "graviballs" with co-authors to be a "seminal work."
ReplyDeleteStill, it is far to say that 99% of cosmologists aren't aware of his work at all (and in fairness, only about three of his papers to date, two very recent, deal with cosmology as opposed to the astrophysics of galaxies).
Also, lots of people who have published "GR can explain dark matter and dark energy" using different aspects of GR that don't actually work have been quickly shot down with criticism papers, while no one has published any criticism of his work either.
The Deur fan club her at DFTI is doing its best and reminding likely allies in the field of his work, but so far, he is still just a voice in the wilderness that not many are listening to.
OK. I am feeling a great deal of frustration with the Deur saga. I lack expertise in the areas of physics relevent to these papers so my judgment of Deur's work lacks a strong foundation. However, I do not judge him as a flake, he has published in good refereed journals, the papers read just fine. He has presented a ton of results. I worry that people think that his work is just MOND when it is not. It is a derivation of MOND from GR in whick self interactions are included. The question is are self interaction effects, through the nonlinearity of GR, as big as he is saying. I cannot judge this but I wish others, versed in these areas, would look into this. I do not think the particle physics people will because they are happy with their current picture, even though they have a complete lack of evidence. It may take someone in GR and particle physics, if there is such. I am at a loss.
ReplyDeleteis Deur model a Geon
ReplyDelete@jd
ReplyDeleteI am right there with you. If, and it is a big if, Deur is right, his work is the biggest thing since Einstein and solves almost all of the big questions in astrophysics and cosmology (except baryogenesis and leptongenesis) in one fell swoop with fewer free parameters than LambdaCDM and the best possible pedigree one could imagine. No more dark matter. No more dark energy. No cosmological constant. Once it became the paradigm it would be very hard to displace because it is just so attractive in range of applicability, in theoretical foundation, in having minimal free parameters, in fitting data. It would also leave very few observational evidence motivated places to look for beyond the Standard Model physics - at least up to the GUT scale.
Of course, it would also trash the life work of a huge freshman lecture hall full of tenured PhDs all over the world. In the front row of that lecture hall would be the authors of some of the leading GR textbooks (e.g. "Gravitation") that strongly imply that this shouldn't work and are a major reason that this line of inquiry hasn't been pursued more intensely.
If he's right, it doesn't undermine just gravitation and astronomy oriented dark matter and dark energy work either. It also undermines the efforts of a lot of particle physicists with new BSM particles or theories, many of which include a dark matter candidate and are observationally justified by that.
His body of work has reached the point where it deserves the attention of better known scholars in the subfield kicking the tires.
Also, even if Deur's work does not flow, for some technical reason, from classical GR as he claims (a claim I am pretty agnostic about), if the phenomenological conclusions from the equations he has come up with a right, his work is still a conservative, very subtle modification of GR that deserves being taken seriously in its own right with GR theory specialists pointing out precisely what he has modified and determining if this modification can be theoretically consistent - with it currently in a limbo similar to renormalization in Quantum Field Theory which was used in very accurate applications long before its mathematical validity was rigorously established.
If I had a few million dollars (which honestly, compared to the cost of big high energy physics experiments and space telescopes is chump change), I'd commission the work of kicking the tires and developing his theories more fully with grant money. But I've just paid for two kids to receive very expensive college educations and I'm not exactly cash rich as a result, so that's an ixnay.
@neo
ReplyDeleteDeur has done some geon work (see https://en.wikipedia.org/wiki/Geon_(physics)), but the gravitational field self-interaction papers are not a geon theory.
@neo Graviballs are geons.
ReplyDeleteI will probably do a separate post on this, but a recent post at the Backreaction blog on the arguments for and against cosmological inflation suggests to me that the number of tenured PhDs who'd see their life's academic work trashed if Deur is right is not a "big freshman lecture hall" (hundreds to low thousands) but instead, something more on the scale of a major basketball or hockey stadium (in the tens of thousands).
ReplyDeletehttps://backreaction.blogspot.com/2022/03/did-early-universe-inflate.html
@andrew
ReplyDeletegeon theory is gravitational field self-interaction so how is Deur's theory differ?
his paper seems to suggest that the third peak of the CMB, which is explained in terms of dark matter is explained in terms of geons.
how does Deur explanation for CMB differ from saying geons are responsible for the third peak? or even black holes?
aren't black holes powerful gravitational field self-interaction?
his paper could be combined with
The origin of the MOND critical acceleration scale
David Roscoe arXiv:2111.01700
Gravitational force distribution in fractal structures
A. Gabrielli, F. Sylos Labini, S. Pellegrini
Gravitational force distribution in fractal structures - NASA/ADS
http://ui.adsabs.harvard.edu › abs › abstract
by A Gabrielli · 1999 · Cited by 28 — We study the (Newtonian) gravitational force distribution arising from a fractal set of sources. We show that, in the case of real structures in finite
since this explains ao, which Deur does not do.
maybe Deur +
The origin of the MOND critical acceleration scale
David Roscoe arXiv:2111.01700
Gravitational force distribution in fractal structures
A. Gabrielli, F. Sylos Labini, S. Pellegrini
offers a complete explanation for MOND without modifying GR.
so Deur is using standard Gr
ReplyDeletewhy is his calculated values self interaction differ from other physicist using gr
@neo
ReplyDeleteFirst of all, I am not 100% convinced that Deur is, as claimed, actually using standard GR, although if he is not, the difference is very subtle.
Second, in most astrophysics and cosmology applications, one assumes that the self-interaction is negligible and can be ignored, and so the Newtonian approximation can be used. So, the question is why this was assumed to be negligible. There is even a widely cited "no go theorem" (for which I suspect some conditions are not met in this case) that states that self-interactions shouldn't matter in weak gravitational fields at speeds far less than the speed of light.
If you calculate the self-interaction effect with a small mass and try to scale it, you will wildly underestimate it because it grows in a non-linear way with scale.
It completely cancels out in spherically symmetric systems, and many GR calculations assume spherical symmetry for convenience (non-spherically symmetric systems are much more difficult to calculate and can't necessarily be done analytically and instead you have to do a numerical approximation in many cases) or are calculated using point particles which are, by definition, spherically symmetric.
Also, the relative strength of the first order Newtonian term decreases as a function of 1/r^2, while the second order self-interaction term decreases (in an ideal disk shaped system) as 1/r, with a value much, much less than the Newtonian term in the vicinity of the source, and a meaningful contribution relative to the Newtonian term only far from the source. So, if you look only on a perturbative basis at the strength of the self-interaction term near the gravitational source, it will look negligible.
To get significant self-interactions you need:
1. A larger ratio of M/L where M is the mass of the system and L is its characteristic length,
2. A large deviation from spherical symmetry, and
3. An evaluation of the strength of the source a great distance from the source.
But, in those systems, since gravity is additive and since the geometry doesn't cancel it out, the effect appears to be very significant (I don't really have the expertise to say definitively and confidently that this is correct but I haven't seen anyone contradict it either).
Third, the way Einstein's equations are usually structured, the self-interaction effects appear on the left hand side, separate from the "source" terms on the right hand side, even though the effect of a gravitational field with X energy should be of the same magnitude and character as, for example, an electromagnetic field with the same X energy that appears in the source term, so the conventional way of stating the equations of GR makes this self-interaction very non-obvious.
A third-party review from a physics student (3rd year undergraduate). https://astrobites.org/2020/08/17/the-alternative-to-dark-matter-may-be-general-relativity-itself/
ReplyDeleteI thought self-interaction occurred in GR since gravity also has energy which causes curvature.
ReplyDeleteso how does Deur explain the CMB third peak ?
is Deur claim that other GR physicist incorrect calculate gravitational energy as too low
ReplyDelete"I thought self-interaction occurred in GR since gravity also has energy which causes curvature."
ReplyDeleteIt does, although this is frequently ignored in cosmology scale calculations on the assumption that it is negligible.
The third-peak is caused because the self-interaction gives rise to dynamics similar to dark matter within galaxies and galaxy clusters, while reducing the interaction between galaxies and galaxy clusters. The current paper and the previous one (on large scale structure formation) spell out how this is done.
"is Deur claim that other GR physicist incorrect calculate gravitational energy as too low"
The claim is that other GR physicists ignore gravitational self-interaction in weak field, low speed systems on the (inaccurate but understandable) assumption that it is negligible in these contexts.
The fact that this is ignored is true. Most astrophysicists use a quasi-Newtonian approximation for cosmology and large scale physics which in part flows from excessive assumptions of spherical symmetry in addition to the weakness of the effect (except that they assume gravitational lensing and red shift of light). Most reserve consideration of self-interaction effects mostly for strong fields like in the near vicinity of bodies like black holes and neutron stars, especially when they merge or closely orbit each other.
The question is whether Deur is right that it shouldn't be ignored when the three conditions mentioned are present, or if he has made an error that overestimates self-interaction effects (in much the way that gravitomagnetic effects arising from the momentum of the rotation of galaxies was overestimated by Cooperstock (2018), and in efforts to explain an atomic scale discrepancy with GR effects recently (in muonic hydrogen nucleus radius measurements, I think, which turned out to actually be an issue with old electronic hydrogen nucleus radius measurements).
Both those produced rapid rebuttal papers, however.
what is deur calculated values for how much gravitational energy for standard galaxies vs. mainstream, which is high enough to replace dark matter
ReplyDeleteThe aggregate gravitational energy for standard galaxies is the same. Increased pull within the galaxy is offset one for one by decreased pull outside the galaxy.
ReplyDeleteThe magnitude of the effect in terms of boost required is pretty modest since it only has an effect outside the MOND threshold at the fringes of the galaxy, rather than being generated by a huge dispersed mass field.
You can read the papers for technical details. I have them all linked at the Deur page in the sidebar.
This paper has enough to do the math. https://arxiv.org/pdf/1909.00095v2.pdf
ReplyDeleteBut a non-symmetrical vector calculus problem isn't something I can do quickly or in my head any more.
Latest version of the paper is https://arxiv.org/abs/1909.00095v3
ReplyDeleteYou might like the presentation in this paper better: https://arxiv.org/pdf/2004.05905.pdf (published in European Journal of Physics).
ReplyDeletethe usual way of explanation for the third peak of the cub is from gravity 5x cold dark matter.
ReplyDeleteis Deur claims that gravitational field self-interactions = gravity 5x cold dark matter in the third peak of the cub
and effects went unnoticed by hundreds of gr experts ?
even the recent papers by Constantinos Skordis and Tom Zlosnik need additional scalar and vector fields explanation for the third peak of the cub
Group think is powerful. If the prevailing wisdom is that you can ignore an effect in certain circumstances, almost everyone will do that, even if its wrong.
ReplyDeleteDeur might very well be wrong. But it really isn't that shocking that a gravitational effect that reproduces dark matter phenomena in galaxies would also do so in CMB contexts. Also, even if Deur is wrong about what GR says, that doesn't mean that he is wrong about what Nature is doing.
does Deur also associated gravity with dark energy
ReplyDeleteYes. So, does LambdaCDM, but Deur does it without a cosmological constant.
ReplyDelete