A LQG Legend Writes Paper Claiming GR Explains Dark Matter Phenomena

[kodama]

Earth is a very different geometry from a galaxy. Earth is spherical to a very good approximation. A galaxy is not; it's a flat disk with some bulge in the center but still very different from spherical. The basic claim of the theorists who are saying that GR nonlinear effects can explain galaxy rotation curves without dark matter is that the relative order of magnitude of those effects, as compared with the usual Newtonian ones, are much larger for a flat disk than for a spherical configuration of matter. I'm not enough of an expert to independently do the calculations, but that's the basis of the claim as I understand it.

MOND requires 1/r in the deep MOND regimen. could s a flat disk explains that

 

[PeterDonis]

MOND requires 1/r in the deep MOND regimen. could s a flat disk explains that

Go read the papers and see. That's basically what they are saying, but they include calculations.

 

[kodama]

Go read the papers and see. That's basically what they are saying, but they include calculations.

does MOND differ depending on location, i.e. 1/r only apply for coplanar stars and not perpendicular to galaxy

 

[PeterDonis]

does MOND differ depending on location, i.e. 1/r only apply for coplanar stars and not perpendicular to galaxy

Go read the papers on MOND and see.

 

[mitchell porter]

A lot of theories and models are being discussed at once in this thread, but (in my opinion) without any clarity or precision. It would help if we could pick out a few, and actually understand them, and how they differ. I would nominate (1) the textbook weak-field models described by Ciotti in #44 (2) Ludwig's model, as an exemplar of gravitomagnetic models (3) whatever it is that Deur is doing.

Regarding (1) and (2), Ciotti apparently carries out gravitomagnetic calculations in the context of ordinary textbook models, and obtains that the force is minuscule. But cautiously, he does not say that this refutes Ludwig, since he knows that Ludwig has a different starting point. He says only that it would be very surprising if a different kind of approximation led to such a different result from the textbook results, for weak fields.

So this raises the question that Robin Hanson tried to answer (#41, #42): exactly what is different about Ludwig's assumptions, that makes them capable of producing such a different result? Hanson proposed that it is the assumption of zero pressure, an assumption shared by several other papers cited in this thread. I am wondering if it's initial conditions: maybe if you start with large gravitomagnetic forces, they will continue to be generated, but if you don't, they won't become so strong? Surely, careful study of Ludwig's work, and careful comparison with the textbook models in Ciotti, can yield a definite answer to the question above.

As for (3), Deur's work, it is being described in this thread (#43) as a model which takes into account the "self-interaction" of gravity in general relativity; and it was even suggested (#31) that the conventional wisdom, that gravitational energy in general relativity cannot be localized, has inhibited the study of gravitational self-interaction... I am skeptical about this second claim. There has been plenty of research on nonlinearity in general relativity; there has been plenty of research on stress-energy pseudotensors and partially localized definitions of energy; are there really dramatic new empirical consequences waiting to be revealed, once these two lines of research are considered together?... I also want to understand the relationship between the classical and quantum parts of Deur's research. Hopefully all this can be disentangled with sufficient patience and care.

 

[ohwilleke]

A lot of theories and models are being discussed at once in this thread, but (in my opinion) without any clarity or precision.

Fair enough, although one of my purposes in posting the thread was to illustrate the overall state of the GR effects as DM literature which is quite a bit bigger than a lot of people realize, but apart from Deur and Ludwig, not very sustained and developed, in an effort to identify common themes and contradictions, if any, and also to demonstrate that this is not just one or two isolated individuals pursuing a research program that no one else is exploring (as well as to illustrate the concentration of the work on this research agenda in the time period since 2018 more or less).

I agree that the field itself is scattered and the people involved aren't listening to each other very much.

Deur's work is definitely the most developed line of scholarship in the GR effects cause DM phenomena research agenda, and unlike Ludwig, who is purportedly contradicted by Hanson and Ciotti, there isn't really any work out there engaging with his line of analysis for good or ill, despite the growing number of publications that Deur has made in the field.

Maybe this is because nobody inclined to do so has noticed him, but it also might be because those who have noticed intuitively believe that he must be wrong but haven't taken the time to work through the math because Deur is working with math inspired by QCD and familiar to people in that field but unfamiliar to most people in the heartland of GR theory and phenomenology. So, its a lot more work for them to dig into Deur's analysis than it is for them to work over GEM analysis that is far more familiar to them in Ludwig's papers.

Regarding (1) and (2), Ciotti apparently carries out gravitomagnetic calculations in the context of ordinary textbook models, and obtains that the force is minuscule. But cautiously, he does not say that this refutes Ludwig, since he knows that Ludwig has a different starting point. He says only that it would be very surprising if a different kind of approximation led to such a different result from the textbook results, for weak fields.

So this raises the question that Robin Hanson tried to answer (#41, #42): exactly what is different about Ludwig's assumptions, that makes them capable of producing such a different result? Hanson proposed that it is the assumption of zero pressure, an assumption shared by several other papers cited in this thread. I am wondering if it's initial conditions: maybe if you start with large gravitomagnetic forces, they will continue to be generated, but if you don't, they won't become so strong? Surely, careful study of Ludwig's work, and careful comparison with the textbook models in Ciotti, can yield a definite answer to the question above.

Along that line, one of Ludwig's assumptions, also found in the paper in #1 that started this thread, is that the system is "rotationally supported" which goes to your initial conditions speculation. GEM may not provide a good source for revving up the spin from a dead halt, but could provide the field needed to sustain it once it is going.

Intuitively, it makes more sense that the rotationally supported assumption matters, than it does that it assumes zero pressure (even though zero pressure seems like a reasonable enough assumption at face value in a spiral galaxy system).

An earlier post also noted, and I don't think it should be dropped, the importance of assumptions about the geometry of the system (disk-like in Ludwig and the paper in #1 v. spherical in many other treatments) which is almost surely a material assumption.

As for (3), Deur's work, it is being described in this thread (#43) as a model which takes into account the "self-interaction" of gravity in general relativity . . . I also want to understand the relationship between the classical and quantum parts of Deur's research. Hopefully all this can be disentangled with sufficient patience and care.

One important aspect of Deur's earlier quantum oriented work is that it is modeled in a static equilibrium model that explicitly disregards GEM effects that arise from the motion of the particles in the system. Systems not near equilibrium are expressly noted by Deur in those papers to be beyond the scope of applicability of his quantum oriented work.

(Incidentally, there is some MOND scholarship by Stacey McGaugh and others that also observes that MOND does not hold in systems not close to equilibrium and even uses a poor MOND fit as a flag that a system might be out of equilibrium. I won't cite it here as MOND itself is really off topic to this thread. This is notable, however, because, in the geometry of a spiral galaxy Deur's approach with pure GR closely approximates MOND, and Deur's approach could provide a solid GR theoretical basis for the MOND conclusions while expanding its domain of applicability in systems like galaxy clusters where MOND underperforms by resorting to the different geometry of the mass in these systems.)

In Deur's classical work, different simplifications, in addition to or in lieu of the static equilibrium assumption of the quantum work, are used in ways that less transparently differentiate gravitational field self-interaction from GEM effects. Crosta and Balasin in #2, for example, also make a static equilibrium analysis that cannot be due to GEM effects (and like Deur, have not triggered refutation papers.)

(I'm also not entirely convinced that the GEM effects aren't, through some back door in the equations, basically harnessing gravitational field self-interactions, particularly if the initial conditions in the GEM works turns out to be the key different assumption. Deur's quantum work makes it seem unlikely to me that the reverse, that his self-interaction effect is really a backdoor implicating GEM effects, is true).

Deur's recently published classical paper at #1, Alexandre Deur, "Relativistic corrections to the rotation curves of disk galaxies" (April 10, 2020) (lated updated February 8, 2021 in version accepted for publication in Eur. Phys. Jour. C)., uses a mean field approximation to do the GR analysis.

Some different methodological tools were used in the working paper, A. Deur, Corey Sargent, Balša Terzić, "Significance of Gravitational Nonlinearities on the Dynamics of Disk Galaxies" (August 31, 2019, last revised January 11, 2020) (pre-print). Latest update May 18, 2020. https://arxiv.org/abs/1909.00095v3

Some key points from the body text:

The rotation curves of several disk galaxies were computed in (Deur 2009) based on Eq. (1) and using numerical lattice calculations in the static limit (Deur 2017). . . . Although based directly on the GR’s Lagrangian, the lattice approach is limited since it is computationally costly and applies only to simple geometry, limiting the study to only a few late Hubble type galaxies at one time. To study the correlation from MLS2016 over the wide range of disk galaxy morphologies, we developed two models based on: 1) the 1/r gravitational force resulting from solving Eq. (1) for a disk of axisymmetrically distributed matter; and 2) the expectation that GR field self-interaction effects cancel for spherically symmetric distributions, such as that of a bulge, restoring the familiar 1/r 2 force.

and from the appendix:

The direct calculation of the effects of field self-interaction based on Eq. (1) employs the Feynman path integral formalism solved numerically on a lattice. While the method hails from quantum field theory, it is applied in the classical limit, see (Deur 2017). The first and main step is the calculation of the potential between two essentially static (v c) sources in the non-perturbative regime. Following the foremost non-perturbative method used in QCD, we employ a lattice technique using the Metropolis algorithm, a standard Monte-Carlo method (Deur 2009, 2017). The static calculations are performed on a 3-dimensional space lattice (in contrast to the usual 4-dimensional Euclidian spacetime lattice of QCD) using the 00 component of the gravitational field ϕµν. This implies that the results are taken to their classic limit, as it will be explained below. Furthermore, the dominance of ϕ00 over the other components of the gravitational field simplifies Eq (1) in which [ϕ n∂ϕ∂ϕ] → anϕ n 00∂ϕ00∂ϕ00, with an a set of proportionality constants. One has a0 ≡ 1 and one can show that a1 = 1 (Deur 2017).

 

[kodama]

A lot of theories and models are being discussed at once in this thread, but (in my opinion) without any clarity or precision. It would help if we could pick out a few, and actually understand them, and how they differ. I would nominate (1) the textbook weak-field models described by Ciotti in #44 (2) Ludwig's model, as an exemplar of gravitomagnetic models (3) whatever it is that Deur is doing.

Regarding (1) and (2), Ciotti apparently carries out gravitomagnetic calculations in the context of ordinary textbook models, and obtains that the force is minuscule. But cautiously, he does not say that this refutes Ludwig, since he knows that Ludwig has a different starting point. He says only that it would be very surprising if a different kind of approximation led to such a different result from the textbook results, for weak fields.

So this raises the question that Robin Hanson tried to answer (#41, #42): exactly what is different about Ludwig's assumptions, that makes them capable of producing such a different result? Hanson proposed that it is the assumption of zero pressure, an assumption shared by several other papers cited in this thread. I am wondering if it's initial conditions: maybe if you start with large gravitomagnetic forces, they will continue to be generated, but if you don't, they won't become so strong? Surely, careful study of Ludwig's work, and careful comparison with the textbook models in Ciotti, can yield a definite answer to the question above.

As for (3), Deur's work, it is being described in this thread (#43) as a model which takes into account the "self-interaction" of gravity in general relativity; and it was even suggested (#31) that the conventional wisdom, that gravitational energy in general relativity cannot be localized, has inhibited the study of gravitational self-interaction... I am skeptical about this second claim. There has been plenty of research on nonlinearity in general relativity; there has been plenty of research on stress-energy pseudotensors and partially localized definitions of energy; are there really dramatic new empirical consequences waiting to be revealed, once these two lines of research are considered together?... I also want to understand the relationship between the classical and quantum parts of Deur's research. Hopefully all this can be disentangled with sufficient patience and care.

does the energy in empty space, the cosmological constant, gravitate, and contribute to "self-interaction" of gravity in general relativity

for that matter, does the cosmological constant interact with GEM at cosmological distances

if the space of an entire galaxy that contains the cosmological constant also rotates with the galaxy, doesn't this also produce a GEM effect and also a self-interaction of gravity effect

 

[ohwilleke]

does the energy in empty space, the cosmological constant, gravitate, and contribute to "self-interaction" of gravity in general relativity

for that matter, does the cosmological constant interact with GEM at cosmological distances

if the space of an entire galaxy that contains the cosmological constant also rotates with the galaxy, doesn't this also produce a GEM effect and also a self-interaction of gravity effect

Deur is modeling GR without a cosmological constant.

 

[kodama]

Deur is modeling GR without a cosmological constant.

Emergent Gravity and the Dark Universe arXiv:1611.02269​

we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional `dark' gravitational force describing the `elastic' response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton's constant and the Hubble acceleration scale a_0 =cH_0, and provide evidence for the fact that this additional `dark gravity~force' explains the observed phenomena in galaxies and clusters currently attributed to dark matter.

301 citations

Verlinde's entropic gravity proposal makes the cosmological constant central to his MOND like proposal and has 301 citations.

the energy in empty space should curve space time in GR and may even have a GEM component to it. MOND ao is related to the cc.

 

[Nik_2213]

{ My head hurts, my head hurts, my head hurts... }

Does any of these support or falsify the few String Theory versions using Teleparallel Gravity ??

 

[ohwilleke]

{ My head hurts, my head hurts, my head hurts... }

That is the joy of BSM physics! No other reason to do it really.

Does any of these support or falsify the few String Theory versions using Teleparallel Gravity ??

Not really. All of them assume basic GR and not the teleparallel gravity twist on GR.

If one or more of these work, however, it tends to weakens one of the motivations for String Theory, which is to provide a dark matter candidate particle. indeed, some narrow sense Sting Theory investigators claim that the low energy approximation of String Theory must be Supersymmetry, and one of the big arguments for the desirability of BSM Supersymmetry physics has been that it created a dark matter particle candidate. But, if it turns out that dark matter isn't necessary because it is really a GR effect, then this makes new particles that could fill out a dark sector a problem rather than a solution.

 

[mitchell porter]

like Deur, have not triggered refutation papers

I have a feeling there are far more papers with mistakes out there, than there are papers specifically spelling out the mistakes...

Anyway: the issue with all the papers in this thread, or the counterintuitive claim that they share, is the claim of strong GR effects in circumstances where (as Ciotti explains) one only expects weak effects. Any search for a mistake in a specific paper, needs to start by identifying what the alleged mechanism of the strong effects is. For example, in Ludwig it's a gravitomagnetic force that's a million times greater than what you would normally expect (I get this factor from the calculation by Garrett Lisi).

How about Deur? In "Significance of Gravitational Nonlinearities on the Dynamics of Disk Galaxies", Deur et al say:

... one may question the relevance of field self-interaction at large galactic radii r. At these distances, the missing mass problem is substantial, while the small matter density should make the self-interaction effects negligible. The answer is in the behavior of the gravitational field lines; once they are distorted at small r due to the larger matter density, they evidently remain so even if the matter density becomes negligible (no more field self-interaction, i.e., no further distortion of the field lines), preserving a form of potential different from that of Newton. Thus, even if the gravity field becomes weak, the deviation from Newton’s gravity remains.

When it comes to understanding the specific mechanism that Deur proposes, I feel that the key paper is "Self-interacting scalar fields at high temperature". He constructs scalar field theories meant to resemble QCD and GR, and argues that the force potentials they contain will have the same form in the more complex theories. That argument is certainly a natural point of scrutiny - the full theories have extra degrees of freedom, and that can completely change the dynamics.

 

[malawi_glenn]

one of the motivations for String Theory, which is to provide a dark matter candidate particle

Never read that in my string theory books.
Supersymmetric QFT particle models however can provide dark matter candidates, in some region of the models parameter spaces, but they do not have to do that per se.

some narrow sense Sting Theory investigators claim that the low energy approximation of String Theory must be Supersymmetry, and one of the big arguments for the desirability of BSM Supersymmetry physics has been that it created a dark matter particle candidate

What is a string theory "investigator"? Not someone who is a researcher? Who are these narrow sense people, and why are they narrow sensed? Supersymmetry is required in string theory to accommodate fermion particles in the low energy limit, not dark matter candidates.

 

[ohwilleke]

What is a string theory "investigator"? Not someone who is a researcher?

An investigator is basically a scientist but might include, for example, a mathematician who doesn't identify as a scientist. I chose the word to avoid using the word "scientist" for that reason. Researcher means the same thing.

Who are these narrow sense people, and why are they narrow sensed?

The narrow sense people are the people who are working directly with M-theory equations and have a very specific technical definition of what counts as string theory and this definition typically mandates supersymmetry as the low energy limit.

The broad sense people, who also often call themselves string theorists, are people who use concepts from string theory, like a massless spin-2 graviton, or 11 dimensional space, or a minimum sized one dimensional particle, or computational methods, but don't necessarily put it in the context of a specific overall comprehensive theoretical structure intended to be a complete Theory of Everything.

Supersymmetry is required in string theory to accommodate fermion particles in the low energy limit, not dark matter candidates.

Supersymmetry, by definition, supplies BSM fundamental particles. They don't always provide dark matter candidates and that wasn't the original justification for supersymmetry. But supersymmetry advocates generally touts the existence of dark matter candidates as one of the reasons to take the theory seriously and to find it desirable to pursue. If one or more of the supersymmetric fundamental particles cannot decay to SM particles, the lightest supersymmetric particle (LSP) is a prime dark matter candidate (although less so now that direct detection experiments have ruled out supersymmetric WIMPS since supersymmetric WIMPS have to interact via the weak force at the same strength as a neutrino).

Now that supersymmetric particles haven't been discovered at the masses where they would be expected to address the hierarchy problem that motivated supersymmetry in the first place, the feature that they generically provide DM candidates has become much more important in making the case of supersymmetry and by association, string theory.

 

[ohwilleke]

When it comes to understanding the specific mechanism that Deur proposes, I feel that the key paper is "Self-interacting scalar fields at high temperature". He constructs scalar field theories meant to resemble QCD and GR, and argues that the force potentials they contain will have the same form in the more complex theories. That argument is certainly a natural point of scrutiny - the full theories have extra degrees of freedom, and that can completely change the dynamics.

This would seem like more of a concern if the same result weren't reproduced with classical GR.

 

[malawi_glenn]

An investigator is basically a scientist but might include, for example, a mathematician who doesn't identify as a scientist. I chose the word to avoid using the word "scientist" for that reason. Researcher means the same thing.

Use standard lingo instead.

Supersymmetry, by definition, supplies BSM fundamental particles.

Yes but that is residual. You made it sound like (super)string theory was motivated by the need of having a dark matter particle candidate.

 

[ohwilleke]

Use standard lingo instead.

investigator is very standard lingo. I've lived in and around academia since I was a toddler. It is used all the time.

Yes but that is residual. You made it sound like (super)string theory was motivated by the need of having a dark matter particle candidate.

I said, "it tends to weakens one of the motivations for String Theory, which is to provide a dark matter candidate particle" and it is one of the modern motivations for String Theory.

 

[malawi_glenn]

it is one of the modern motivations for String Theory

I guess I have to contact my old friends at the university again and make them list the top 5 motivations for string theory. What does "modern" mean in this context?
My newest String Theory book is from 2012 (Peter Wests book), is there any newer I should get you think?

 

[ohwilleke]

I guess I have to contact my old friends at the university again and make them list the top 5 motivations for string theory. What does "modern" mean in this context?
My newest String Theory book is from 2012 (Peter Wests book), is there any newer I should get you think?

It is a motivation in arguments that there is any observational support for thinking that there is an observational evidence to motivate BSM physics that Sting Theory could explain, and hence for taking it seriously. I agree that it didn't motivate the initial formulation of the theory.

 

[mitchell porter]

This would seem like more of a concern if the same result weren't reproduced with classical GR.

Are you referring to "Relativistic corrections to the rotation curves of disk galaxies"?

Deur says in the summary that the method in this paper is "less directly based on GR’s equations than the path integral approach" (the latter refers to lattice calculations of the kind discussed in the "scalar fields" paper). He describes this new method as "a mean-field technique combined with gravitational lensing". I haven't quite figured out how it works. Although he talks about curvature, I don't see a metric anywhere in the paper.

From what I can see, he models the galaxy as a disk-shaped distribution of mass, then calculates how lines of flight radiating outward from the center would be warped by this mass distribution, then says that this is how gravitational field lines would behave due to self-interaction, and calculates a gravitational force from the flux of field lines. There must be a way of judging whether this is what GR actually predicts... At least Deur's paradigm is getting clearer to me now.

 

[malawi_glenn]

It is a motivation in arguments that there is any observational support for thinking that there is an observational evidence to motivate BSM physics that Sting Theory could explain, and hence for taking it seriously. I agree that it didn't motivate the initial formulation of the theory.

Do you have any other source where a string theorist lists dark matter particle candidate as a modern motivation?

 

[kodama]

Do you have any other source where a string theorist lists dark matter particle candidate as a modern motivation?

Brian Green and Michio Kaku mention WIMPS and dark matter in their popular books

 

[malawi_glenn]

Brian Green and Michio Kaku mention WIMPS and dark matter in their popular books

I am sure they do, but popular books are ... well ... not a good source of information ...
Let's say I want to fund a string theory research (investigation) group, and I need to write a funding proposal. Should I use those books as a source?

Remember the movie "limitless"? Where the main characters friend /or was it sister...) said he/she read Brian Greenes book in just one day? Why not read GREENs books on Superstring theory? The real deal so to say. I just thought this was a fun anectode.

 

[Davephaelon]

When I first came across Deur's work based on self-interacting gravitons, in analogy with QCD, I was astounded by its elegant simplicity in explaining, for example, the excess orbital velocities of galaxies within a galaxy cluster. Here he invokes flux tubes to account for the additional gravitational attraction between 'point like' galaxies above what would be expected in classical Newtonian gravity. But as evidenced by gravitational lensing a cluster's gravity is enhanced beyond its periphery. It struck me that the extra gravitational potential from the flux tube mechanism would only apply between galaxies but not add to the gravity potential beyond the cluster. It's inconceivable that professor Deur could have overlooked this, so the explanation is probably in one of his papers, which are pretty technical. I'm a bit groggy this morning, but will check later in the morning Ohwilleke's excellent, more layman friendly, write-up on Deur's work to see if I can find something on this.

 

[Davephaelon]

Oops, I see that I already made a query on the issue of explaining enhanced gravity from lensing data beyond the outer boundaries of both galaxies and galaxy clusters, in Deur's SI paradigm, on the thread titled "Do gravitons interact with gravitons". Scanning the responses over there, I see that there is a stackexchange write-up in the last post linked by rcarbajal68 that addresses this issue. I'll give that a lookover.

 

[mitchell porter]

I continue to think it's extremely unlikely that general relativity actually predicts what Deur says it predicts.

More precisely:

@ohwilleke is our best authority on Deur's work. He says (#65 in this thread) that Deur claims these effects occur even in the classical theory. I tried to work out the alleged mechanism in #70.

It must be possible to judge whether this is a reasonable claim, even without exact solutions. Hawking and Penrose proved their singularity theorems by reasoning about geodesics. Surely there's some way to place bounds on what amplified nonlinearity in classical GR can accomplish (perhaps something involving Lyapunov exponents?).

Then there's the quantum version of Deur's arguments. Here the paper I mention in #62 might contain the detailed arguments. Again I am skeptical - yes, gravitons should interact with gravitons, but the interaction ought to be extraordinarily weak, because of the extreme smallness of the gravitational coupling constant. Maybe there's more opportunity for extremely strong nonperturbative effects, e.g. if the gravitational coupling constant runs to large values at small enough scales.

But overall I'm still skeptical here, too. If I ever get around to checking, I might start by investigating whether the approximation of a tensor field (the metric) by a scalar, is messing up the dynamics by introducing an unjustified constraint. (Reducing a tensor to a scalar is a massive truncation of the physical state space, and needs to have a dynamical justification, i.e. there needs to be some cause actively preventing the other degrees of freedom from acquiring forbidden values.)

By the way, what I'm saying is not quite the same as saying that Deur is completely wrong. His calculations could be wrong in general relativity (classical or quantum), but might be right in some other theory of gravity.

 

[ohwilleke]

I continue to think it's extremely unlikely that general relativity actually predicts what Deur says it predicts.

Fair. I certainly don't have the capacity to evaluate that rigorously. There are quite a few papers that he has published in peer reviewed journals and he is a professional full time physicist, so surely this work isn't wildly off the mark. But GR is notorious for being an area where very subtle issues of characterization can make a big difference.

By the way, what I'm saying is not quite the same as saying that Deur is completely wrong. His calculations could be wrong in general relativity (classical or quantum), but might be right in some other theory of gravity.

This is indeed an important point. If you've got gravitational equations that can describe phenomena attributed to dark matter and dark energy over a very great range of applicability, is relativistic in the general sense, can reproduce the CMB and address issues like the impossible early galaxies problem, even if it deviates from Einstein's Field Equations as conventionally applied, then Deur still has a winner, even if he somewhat misunderstands the nature of why his calculations work, and Einstein's Field Equations are probably not quite the right description of reality even though they are really close and excellent in some domains of applicability like strong gravitational fields.

The possibility that the results are really primarily a quantum gravity specific effect are among the possibilities that could make sense.

On the other hand, it is frustrating that there isn't more third-party examination of what is really one of the most promising dark matter particle theory alternatives, to vet it and consider it. The more there are published papers that are not refuted, the more he gets co-authors and publication in peer reviewed articles, and the more that dark matter particle theories and LambdaCDM fall short, the more this work deserves expert attention from GR specialists.

 

[ohwilleke]

There has been plenty of research on nonlinearity in general relativity; there has been plenty of research on stress-energy pseudotensors and partially localized definitions of energy; are there really dramatic new empirical consequences waiting to be revealed, once these two lines of research are considered together?... I also want to understand the relationship between the classical and quantum parts of Deur's research. Hopefully all this can be disentangled with sufficient patience and care.

Another thing that has impeded existing research is that the vast majority of GR papers, in order to make their analytical calculations tractable, assume spherically symmetrical systems, which when present, automatically eliminate the self-interaction effects (which makes sense if conventional wisdom tells you that effects from lack of spherically symmetry aren't important and leading textbooks say so in so many words).

One of the reasons Deur investigated non-sphericially symmetric systems, which GR researchers avoid for convenience in a very large share of work examining how conventional GR as opposed to modifications of it work, is that in QCD (which is his primary specialty in physics) you simply can't do that and get useful results, so he's used to strategies for modeling non-spherically symmetric systems mathematically with which the run of the mill GR researcher is not.

 

[timmdeeg]

This whole discussion doesn't seem to clarify how Deur's gravitational field self-interaction really works.

Apart from this the predictions regarding CMB and Supernovae data are astonishing:

FIG. 2: Power spectrum of the CMB temperature anisotropy FIG. 3: Left panel: Supernova apparent magnitudes vs. redshift.

I wonder if what he calls "the present calculation" shouldn't yield the values of the Hubble "constant" for the early universe und for our local universe too.

Does anyone know if and how Deur's work contributes to resolve the ongoing Hubble-Tension?

 

[ohwilleke]

Does anyone know if and how Deur's work contributes to resolve the ongoing Hubble-Tension?

He hasn't written on the topic yet.

The Hubble constant is not definitionally constant in his work, as phenomena attributed to dark energy in his work are emergent from the emergence of galaxy and large scale structure rather than than being closely related to a cosmological constant term in the equations of GR. So, it might resolve the tension and at a minimum, some sort of tension wouldn't be surprising in his work.

 

[timmdeeg]

He hasn't written on the topic yet.

The Hubble constant is not definitionally constant in his work, as phenomena attributed to dark energy in his work are emergent from the emergence of galaxy and large scale structure rather than than being closely related to a cosmological constant term in the equations of GR. So, it might resolve the tension and at a minimum, some sort of tension wouldn't be surprising in his work.View attachment 315023

http://link.springer.com/content/pdf/10.1140/epjc/s10052-019-7393-0.pdf
Equation (17) yields for present time: 1 = [DM (0)ΩM + DRΩR + DΛΩΛ] − K a2 0 H2 0 , (22)

Sorry I didn't transfer this into Latex.

(17) yields the present time (late universe) Hubble constant expressed by the depletion function$D_M$, whereby $\Omega_R=0$ and $\Omega_{\Lambda}=0$ .

Deur doesn't show a value for $H_0$ explicitly. As he reproduces the supernovae data correctly would this imply the correctness of the late universe Hubble constant, presently around 73 (km/s)/Mpc?

But what if it turns out that the supernovae distance ladder has some systematic failure and thus $H_0$ changes accordingly. Would this eventually support Deur's self-interaction Hypothesis?

 

[ohwilleke]

http://link.springer.com/content/pdf/10.1140/epjc/s10052-019-7393-0.pdf
Equation (17) yields for present time: 1 = [DM (0)ΩM + DRΩR + DΛΩΛ] − K a2 0 H2 0 , (22)

Sorry I didn't transfer this into Latex.

(17) yields the present time (late universe) Hubble constant expressed by the depletion function$D_M$, whereby $\Omega_R=0$ and $\Omega_{\Lambda}=0$ .

Good catch.

Deur doesn't show a value for $H_0$ explicitly. He reproduces the supernovae date correctly. Would this imply the correctness of the late universe Hubble constant, presently around 73 (km/s)/Mpc?

But what if it turns out that the supernovae distance ladder has some systematic failure and thus $H_0$ changes accordingly. Would this eventually support Deur's self-interaction Hypothesis?

It would take a lot more careful analysis and review of that paper for me to tell. Deur's approach does address consistently with the evidence and contrary to LambdaCDM address the impossible early galaxies problem as well as CMB, so it may very well be consistent.

 

[kodama]

He hasn't written on the topic yet.

if dark matter is discovered and explains everything it is said to does that mean Deur is wrong

 

[ohwilleke]

if dark matter is discovered and explains everything it is said to does that mean Deur is wrong

Yes. That would be awesome if it happened. I don't think it will in the next three decades or so.

 

[kodama]

Yes. That would be awesome if it happened. I don't think it will in the next three decades or so.

sterile neutrinos, axions, wimps, even black hole and x17-z'

 

[timmdeeg]

It would proof that Deur's GR field self-interaction mimicking several times the amount of baryonic matter isn't more than a notion but a wrong one.

It seems in GR there is no rigorous calculation instead there is the analogy to QCD whereby Deur refers to a similarity of the Lagrangian. Whereas in QCD the field-interaction exists and is described undoubtedly.

I'm not sure about this: Would field-self-interaction in GR necessarily imply the existence of gravitons?

Is all this the weak point which causes silence in the community?

 

[Davephaelon]

I am greatly impressed by Deur's hypothesis, inasmuch as it conforms to Occam's Razor of minimal assumptions yielding maximum explanatory power. It's remarkable that with gravitational self-interaction alone one can resolve most of the puzzles that have confronted astrophysicists tracing back almost a century. But I say this as one who doesn't have a deep understanding of GR, so I cannot gauge whether his extrapolation of QCD phenomena into the cosmic arena is fully valid. Hopefully, physicists who are specialists in GR will examine his papers and provide us a more rigorous assessment of the plausibility of the ideas expressed in them.

 

[timmdeeg]

if dark matter is discovered and explains everything it is said to does that mean Deur is wrong

Or the other way round. Would dark matter be disproved if astronomers discover that what seems to be dark matter depends on symmetry properties of a matter distribution as predicted by Deur's field self-interaction SI?

... the expectation that GR field selfinteraction effects cancel for spherically symmetric distributions ...

In contrast in flat galaxies SI doesn't cancel mimicking a large amount of dark matter hence.

 

[ohwilleke]

It seems in GR there is no rigorous calculation instead there is the analogy to QCD whereby Deur refers to a similarity of the Lagrangian. Whereas in QCD the field-interaction exists and is described undoubtedly.

There are calculations using a mean-field approximation of classical GR fields and using the GR Lagrangian, in a static approximation (i.e. ignoring particle momentum contributions and electromagnetic flux contributions to the mass-energy tensor on the right hand side of Einstein's equations). QCD motivates the approach taken but isn't actually being used at all to make the calculations.

As a practical matter, it isn't possible to calculate GR effects analytically (i.e. by working out equations rather than doing N-body calculations or some other numerical method) in complex systems like a galaxy.

I'm not sure about this: Would field-self-interaction in GR necessarily imply the existence of gravitons?

No.

Is all this the weak point which causes silence in the community?

Probably not. More likely it is due to (1) the fact that Deur is primarily a QCD physicist publishing outside his primary subfield community in a different subfield of physics (the astronomy of galaxies, GR, and astrophysics), and (2) that non-rigorously derived conventional wisdom in GR is that non-Newtonian GR effects are negligible in galaxy and galaxy cluster scale systems.

 

[ohwilleke]

sterile neutrinos, axions, wimps, even black hole and x17-z'

Narrow sense WIMPs (e.g. supersymmetric WIMPs), and primordial black holes are basically entirely ruled out by existing observations.

Previous experimental hints of sterile neutrinos have likewise been all but ruled out and have found alternative explanations, although neutrino physics researchers continue to look for sterile neutrinos as explanations for new anomalies. Right handed neutrino theories are also exceedingly popular among theorists trying to devise grand unified theories, and among physicists proposing see saw mechanism for neutrino mass.

Any sterile neutrino dark matter candidate has to propose a creation method for them other than thermal freeze out, because something with a sterile neutrino mass suggested by neutrino research would give rise to "hot dark matter" which is inconsistent with the amount of galaxy scale structure observed.

Also, generically, even if sterile neutrinos (or any more massive DM particle) had mean velocities consistent with warm dark matter or cold dark matter, any dark matter particle solution needs to have some kind of self-interaction and/or interaction with ordinary matter sufficient to explain the dark matter halo shapes/distributions that are inferred from astronomy observations. Without that you get NFW halo distributions which are contrary to astronomy observations, and you don't explain the tight link between inferred DM distributions and observed baryonic matter distributions. These problems are generically a problem with a wide array of particle dark matter candidates.

The X17 boson proposed to explain some subtle kinematics of nuclear matter decays interacts too strongly with other matter to be a dark matter candidate.

Likewise, a Z' boson with a different mass than a Z boson, but weak force interactions of a similar magnitude to a Z boson is likewise ruled out by direct DM detection searches, at least in the 1 GeV to 1000 GeV mass range that is usually assumed for a Z' boson, although like any hypothetical particle you can assign pretty much any properties to it to try to fit the data.

Axion-like particle (ALP) dark matter candidate properties are even more ill-defined, and while all are very light there are many, many orders of magnitude of parameter space open. Lots and lots of direct searches from ALP have come up empty, but most of the searches cover only tiny parts of the parameter space. ALPs are also ill motivated in the large part of the parameters space currently being proposed that have nothing to do with the original justification for them to cause the QCD force to have no CP violation.

At some point, ALP DM and effects of gravitons in a quantum gravity regime become hard to distinguish, so the search for ALPs if, in fact, DM effects are really gravitational, may be one of the longest lived DM candidates.

 

[ohwilleke]

This whole discussion doesn't seem to clarify how Deur's gravitational field self-interaction really works.

I have put together an annotated bibliography of the relevant papers along with some prefatory explanations that draw mostly upon one of his power point presentations, to allow anyone who is interested to get a better grasp of these points.

 

[timmdeeg]

I have put together an annotated bibliography of the relevant papers along with some prefatory explanations that draw mostly upon one of his power point presentations, to allow anyone who is interested to get a better grasp of these points.

Very informative, thanks.

 

[kodama]

The X17 boson proposed to explain some subtle kinematics of nuclear matter decays interacts too strongly with other matter to be a dark matter candidate.

High Energy Physics - Experiment​

[Submitted on 29 Sep 2022]

Dark sector studies with the PADME experiment​

A.P. Caricato, M. Martino, I. Oceano, S. Spagnolo, G. Chiodini, F. Bossi, R. De Sangro, C. Di Giulio, D. Domenici, G. Finocchiaro, L.G. Foggetta, M. Garattini, A. Ghigo, P. Gianotti, T. Spadaro, E. Spiriti, C. Taruggi, E. Vilucchi, V. Kozhuharov, S. Ivanov, Sv. Ivanov, R. Simeonov, G. Georgiev, F. Ferrarotto, E. Leonardi, P. Valente, E. Long, G.C. Organtini, G. Piperno, M. Raggi, S. Fiore, P. Branchini, D. Tagnani, V. Capirossi, F. Pinna, A. Frankenthal

The Positron Annihilation to Dark Matter Experiment (PADME) uses the positron beam of the DAΦNE Beam-Test Facility, at the Laboratori Nazionali di Frascati (LNF) to search for a Dark Photon A′. The search technique studies the missing mass spectrum of single-photon final states in e+e−→A′γ annihilation in a positron-on-thin-target experiment. This approach facilitates searches for new particles such as long lived Axion-Like-Particles, protophobic X bosons and Dark Higgs. This talk illustrated the scientific program of the experiment and its first physics results. In particular, the measurement of the cross-section of the SM process e+e−→γγ at s√=21 MeV was shown.

Subjects:	High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Cite as:	arXiv:2209.14755 [hep-ex]
	(or arXiv:2209.14755v1 [hep-ex] for this version)
	https://doi.org/10.48550/arXiv.2209.14755

High Energy Physics - Phenomenology​

[Submitted on 19 Sep 2022]

Resonant search for the X17 boson at PADME​

Luc Darmé, Marco Mancini, Enrico Nardi, Mauro Raggi

We discuss the experimental reach of the Frascati PADME experiment in searching for new light bosons via their resonant production in positron annihilation on fixed target atomic electrons. A scan in the mass range around 17 MeV will thoroughly probe the particle physics interpretation of the anomaly observed by the ATOMKI nuclear physics experiment. In particular, for the case of a spin-1 boson, the viable parameter space can be fully covered in a few months of data taking.

Comments:	8 pages, 5 figures and 1 table
Subjects:	High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as:	arXiv:2209.09261 [hep-ph]
	(or arXiv:2209.09261v1 [hep-ph] for this version)
	https://doi.org/10.48550/arXiv.2209.09261

if x17 exist as a spin-1 boson it could be part of a larger dark sector

" In particular, for the case of a spin-1 boson, the viable parameter space can be fully covered in a few months of data taking. "

we'll see possible announced within a year (In particular, for the case of a spin-1 boson)

 

[ohwilleke]

High Energy Physics - Experiment​

[Submitted on 29 Sep 2022]

Dark sector studies with the PADME experiment​

A.P. Caricato, M. Martino, I. Oceano, S. Spagnolo, G. Chiodini, F. Bossi, R. De Sangro, C. Di Giulio, D. Domenici, G. Finocchiaro, L.G. Foggetta, M. Garattini, A. Ghigo, P. Gianotti, T. Spadaro, E. Spiriti, C. Taruggi, E. Vilucchi, V. Kozhuharov, S. Ivanov, Sv. Ivanov, R. Simeonov, G. Georgiev, F. Ferrarotto, E. Leonardi, P. Valente, E. Long, G.C. Organtini, G. Piperno, M. Raggi, S. Fiore, P. Branchini, D. Tagnani, V. Capirossi, F. Pinna, A. Frankenthal

Subjects:	High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
Cite as:	arXiv:2209.14755 [hep-ex]
	(or arXiv:2209.14755v1 [hep-ex] for this version)
	https://doi.org/10.48550/arXiv.2209.14755

High Energy Physics - Phenomenology​

[Submitted on 19 Sep 2022]

Resonant search for the X17 boson at PADME​

Luc Darmé, Marco Mancini, Enrico Nardi, Mauro Raggi

Comments:	8 pages, 5 figures and 1 table
Subjects:	High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as:	arXiv:2209.09261 [hep-ph]
	(or arXiv:2209.09261v1 [hep-ph] for this version)
	https://doi.org/10.48550/arXiv.2209.09261

if x17 exist as a spin-1 boson it could be part of a larger dark sector

" In particular, for the case of a spin-1 boson, the viable parameter space can be fully covered in a few months of data taking. "

we'll see possible announced within a year (In particular, for the case of a spin-1 boson)

The odds of it not being ruled out are on the order of 0.01%

 

[kodama]

The odds of it not being ruled out are on the order of 0.01%

0.01% is pretty good compare with other BSM physics like EW scale SUSY, LUX dark matter detection, etc.

"the viable parameter space can be fully covered in a few months of data taking. "

0.01% for a chance of one of the biggest mysteries solved with in a year's time

0.01% seems much higher than other BSM HE-physics

the excitement is we should get some evidence for or ruled out within a year's time. i plan to check for updates once a month.

 

[Hornbein]

It seems to me that this question could be answered by examining rotation curves in spherical galaxies. Surely this has been done.

 

[ohwilleke]

It seems to me that this question could be answered by examining rotation curves in spherical galaxies. Surely this has been done.

Few galaxies are totally spherical, but observations have done the next best thing.

Deur has shown rather rigorously that the more spherical a galaxy is the less inferred dark matter content it has:

Observations indicate that the baryonic matter of galaxies is surrounded by vast dark matter halos, which nature remains unknown. This document details the analysis of the results published in MNRAS 438, 2, 1535 (2014) reporting an empirical correlation between the ellipticity of elliptical galaxies and their dark matter content. Large and homogeneous samples of elliptical galaxies for which their dark matter content is inferred were selected using different methods. Possible methodological biases in the dark mass extraction are alleviated by the multiple methods employed. Effects from galaxy peculiarities are minimized by a homogeneity requirement and further suppressed statistically. After forming homogeneous samples (rejection of galaxies with signs of interaction or dependence on their environment, of peculiar elliptical galaxies and of S0-type galaxies) a clear correlation emerges. Such a correlation is either spurious --in which case it signals an ubiquitous systematic bias in elliptical galaxy observations or their analysis-- or genuine --in which case it implies in particular that at equal luminosity, flattened medium-size elliptical galaxies are on average five times heavier than rounder ones, and that the non-baryonic matter content of medium-size round galaxies is small. It would also provides a new testing ground for models of dark matter and galaxy formation.

A. Deur, "A correlation between the dark content of elliptical galaxies and their ellipticity" (October 13, 2020).

Milgrom concluded that elliptical galaxies would have a much lower mass to light ratio than spiral ones back in 1983 with MOND (which is also true), but Deur's finding is more fine grained.

 

[Hornbein]

That seems "highly suggestive."

 

[ohwilleke]

That seems "highly suggestive."

Of course, the thing is that the strong correlation that is observed between galaxy shape and mass to light ratio, which implies in a dark matter particle scenario, the proportion of dark matter and ordinary matter in ay particular galaxy, has no good explanation.

Elliptical galaxies, generally speaking, tend to be larger than spiral galaxies. In a standard galaxy mass assembly scenario in the dark matter particle paradigm, they are formed by the mergers of smaller galaxies. So, they really ought to have all of the DM of their ancestors, rather than than much less.

 

[mitchell porter]

This whole discussion doesn't seem to clarify how Deur's gravitational field self-interaction really works.

In #62, #70, #76, I tried to identify Deur's methods of calculation. And a reminder, Ciotti #44 is the most thorough statement so far, of why one would not expect classical GR to produce such effects. So that's the gap one could try to bridge.

Also, even if that's not how GR works, one could try to design a modified gravity in which Deur's calculations *are* correct.