The Italian research center SISSA has announced a paper proposing a new property, called "non-minimal coupling" [PDF - 232Kb] to address the mystery of the nature of dark matter:
In the Universe, dark matter and standard matter "talk" to each other using a secret language. This "discussion" happens thanks to gravity, scientists say, but not in a way they can fully comprehend. A new SISSA study published in "The Astrophysical Journal" sheds light on this long-standing issue.
The authors of the research, Ph.D Student Giovanni Gandolfi and supervisors Andrea Lapi and Stefano Liberati, propose a special property for dark matter called a "non-minimal coupling with gravity". This new type of interaction can modify dark matter gravitational influence on standard 'baryonic' matter.
[...] To prove the hypothesis, the assumption has been tested and then confirmed with experimental data from thousands of spiral galaxies.
[...] The new study suggests the existence of a new feature of dark matter, named 'non-minimal coupling', which "can be described as a new type of interaction between dark matter and gravity" the authors affirm. "It tells us a lot about the way the two components "communicate". If the non-minimal coupling is present, standard matter "perceives" spacetime in a way which is different from the one "experienced" by the dark matter.
[...] The new study proposes a solution to one of the most discussed problems in astrophysics, researchers say: "Among other things, the positions of those who argue that dark matter does not exist, and therefore gravity must be modified, are based on the difficulty of finding an explanation to this problem, which is one of the last missing pieces for a global comprehension of dark matter".
But there is more. "This feature of dark matter is not a piece of new exotic fundamental physics" the author say. "One can explain the existence of this non- minimal coupling with known physics alone".
Journal Reference:
Giovanni Gandolfi et al Empirical Evidence of Nonminimally Coupled Dark Matter in the Dynamics of Local Spiral Galaxies? [open] 2022 ApJ 929 48
DOI: 10.3847/1538-4357/ac5970
(Score: 1, Informative) by Anonymous Coward on Thursday May 05 2022, @06:41PM (8 children)
is silence. Just like you'd expect from something that isn't.
(Score: 3, Insightful) by Freeman on Thursday May 05 2022, @06:51PM (3 children)
Seems about as reasonable to me as most conclusions and research regarding Dark Matter.
Joshua 1:9 "Be strong and of a good courage; be not afraid, neither be thou dismayed: for the Lord thy God is with thee"
(Score: 3, Funny) by DannyB on Thursday May 05 2022, @08:32PM
Can mere humans even comprehend the compiler errors of the secret dark matter language?
How often should I have my memory checked? I used to know but...
(Score: 0) by Anonymous Coward on Thursday May 05 2022, @09:30PM (1 child)
So what's going on in the Coma cluster of galaxies? Why don't spiral galaxies fly apart? Why do galaxies that are doing gravitational lensing bend light in a way that suggests they have much more mass than is visible? We've got all these measurements of different things, including cosmic microwave background fluctuations that are all consistent with there being a lot of missing mass that is non-baryonic, weakly interacting, and cold. I suppose you could start applying ad hoc changes to gravity models and start applying different relationships acting on different length scales, but that is a hard sell if you're up against an alternative that is largely consistent with all the scenarios. I haven't really figured out why some people have such a hard time with the idea of dark matter. It isn't like there were a bunch of Higgs boson "deniers" around for 50 years before that turned up.
(Score: 3, Funny) by pvanhoof on Friday May 06 2022, @05:43AM
Maybe we should start a flat dark matter society. Dark matter is flat! Dark matter in fact is flying upwards, pushing us all down.
(Score: 0) by Anonymous Coward on Thursday May 05 2022, @10:28PM (3 children)
Then I'm sure you'll provide us with your own hypothesis that explains the observed data.
Yeah, I thought so.
(Score: 1) by BigDog934 on Friday May 06 2022, @06:03PM (2 children)
(Score: 0) by Anonymous Coward on Friday May 06 2022, @11:40PM (1 child)
How does it work?
(Score: 1) by BigDog934 on Saturday May 07 2022, @03:44AM
Well, near as I can tell, it's blah, blah, blah, Rindler horizon, blah, blah, blah, Unruh radiation, blah, blah, blah, Hubble-scale Casimir effect, blah, blah, blah, so, obviously, Quantised Inertia predicts galaxy rotation perfectly without the need for dark matter or any adjustment.
Seriously, read the link. Go to the blog. Anything I put here would be redundant or confused or wrong or all of these things.
(Score: -1, Redundant) by Anonymous Coward on Thursday May 05 2022, @07:09PM
Flooby Dust
(Score: 2) by PinkyGigglebrain on Thursday May 05 2022, @09:42PM
Does it have a secret handshake too?
"Beware those who would deny you Knowledge, For in their hearts they dream themselves your Master."
(Score: 1, Interesting) by Anonymous Coward on Thursday May 05 2022, @09:56PM (1 child)
The idea of non-minimal coupling is that quantum effects can make real particles behave in some ways as though they aren't quite point-like. For example, electrons have a minimal coupling to (interact with) the electromagnetic force described in the Dirac equation. But current flowing through a loop of wire creates a magnetic field, and real electrons behave just a little bit like that. Correcting for this gives you the (more complete) Pauli equation. This is a non-minimal coupling. The effect is small but measurable, and very well established.
I'm not sure what sort of non-minimal coupling is being proposed... since non minimal coupling is a quantum effect, I don't understand how this could work with gravity. And since we can't observe dark matter directly, I'm not sure what experimental evidence they would be able to find. I guess that's why they wrote the paper.
There is an abstract :
https://iopscience.iop.org/article/10.3847/1538-4357/ac5970 [iop.org]
(Score: 3, Informative) by Immerman on Friday May 06 2022, @05:38PM
Well, there's a lot of support for the idea that gravity is a quantum phenomena transmitted by the hypothetical graviton.
The alternative, that gravity is NOT quantum, causes some real conflicts with QM.
For example - as a quantum particle, an electron is inherently non-local - aka it can be (and normally is) in a superposition of states having different locations. The most famous example being that it must simultaneously pass through both slits in a two-slit experiment.
However, an electron also has mass and thus a gravitational field - and if gravity is NOT fundamentally quantum, then the gravitational field can't be in a superposition of states, it can only pull things toward the single definite location where the electron currently is.
I've heard of only two possible ways to resolve non-quantum gravity with QM:
1) Some variation of Bohmian mechanics - essentially the electron is actually a non-quantum particle that always has a definite position and velocity, but is erratically guided by a massless quantum "pilot wave", which is what actually passes through both slits (etc.) to create the observed quantum effects (basically, the wave is a non-local hidden variable - a class of hidden variables we have not been able to rule out)
2) It's actually the tension between QM and gravity that causes quantum decoherence - essentially it's not possible for superposition to force the gravitational uncertainty above some poorly-understood threshold, and trying to do so will cause the wave function to collapse into something whose gravitational uncertainty remains below the threshold. That does offer the benefit of actually explaining why wave function collapse occurs at all - something that's been an ongoing mystery for QM (outside of the many-worlds interpretation, which says it never actually does).
(Score: 2) by Gaaark on Friday May 06 2022, @03:17AM
M.I.S.S.I.N.G.
When they sign the pre-nup, call me.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Friday May 06 2022, @07:36AM (3 children)
...so we make up a factor that makes formula better.
It worked to discover new planets, but it was wrong with epicycles.
(Score: 0) by Anonymous Coward on Friday May 06 2022, @04:08PM (2 children)
Historically, people have used better formulas to grope their way to a better understanding of reality. First there was an understanding of reality with earth at the center, and the heavens painted on a spherical shell. Formulas were developed to describe the movements of the heavens on the shell. These started out as earth centered circles, then sun centered circles, then sun centered ellipses. And it was only at this point, when we had formulas that closely matched reality, that we were able to come up with universal gravitation, an understanding of reality that closely matched the formulas.
(Score: 4, Insightful) by Immerman on Friday May 06 2022, @06:06PM (1 child)
Yep. And then they discovered flaws in Newtonian gravitation - e.g. the precession of Mercury's orbit while being completely unable to find the necessary planet Vulcan nearer to the sun that would explain it. Which hinted that those formula were incomplete, and which gave GR a large credibility boost when it *could* explain the observations.
Then we discovered anomalies in galactic rotation curves that GR couldn't explain without Dark Matter, which we've been completely unable to find, and which cannot readily explain the incredible correlation between rotation curves and visible matter - there's no credible theoretical reason that the amount and distribution of DM in a galaxy should correlate so closely with the amount of visible matter (possibly unless this proposal offers one). There's also the (apparent) cosmic inflation from Dark Energy - which GR technically describes, but only due to a "fudge factor" that Einstein added to his formulas so that they could describe the static universe that was believed to exist at the time.
All of which hints that GR is incomplete - and various alternative theories like MOND seek to offer formulas that better fit the observations.
Basically - formula offer an (often-imperfect) *description* of reality - not a perfect definition. Akin to how a photograph offers an incomplete and imperfect "description" of its subjects.
It used to be that scientists (and science teachers, at least at the university level) routinely qualified their claims with the understanding that all the "Laws" were only the current best-guess approximations of reality. But it's been almost a century now with no major revisions to any fundamental theories outside of Quantum Mechanics (which was improved into Quantum Field Theory), and scientists gradually dropped the qualifiers. I suppose when you're using the same theories as your teacher's teacher's teacher, it's easy to fall into the intellectual laziness of accepting them as Truth - despite that concept being antiethical to the principles of science.
(Score: 2) by crafoo on Friday May 06 2022, @07:35PM
Great post. Take heart. My professors routinely made the qualification your describe. It was a public university, no less. It's been awhile though, and I've heard universities are significantly worse now, so who knows.