This is a quick post to announce that on Monday, April 7 there will be a virtual panel discussion about dark matter and MOND involving Scott Dodelson and myself. It will be moderated by Orin Harris at Northeastern Illinois University starting at 3pm US Central time*. I asked Orin if I should advertise it more widely, and he said yes – apparently their Zoom set up has a capacity for a thousand attendees.
See their website for further details. If you wish to attend, you need to register in advance.
*That’s 4PM EDT to me, which is when I’m usually ready for a nap.
Mildly disappointing that this is (or seems to be) only about cosmological aspects. A similar discussion, focusing strictly on whether particle Dark Matter is/isn’t plausible for explaining galactic rotation curves and galactic lensing, would be “entertaining”. 😉
I have not been asked to limit my discussion to cosmological aspects.
Then I hope you get to enlighten the Scott and audience about the astonishing results of Tobias Mistele and your colleagues. I’d bet that Scott hasn’t even heard of them, or else doesn’t comprehend their full implications.
I wonder whether Orin knows about those results. I haven’t heard any science-oriented youtuber (except Sabine) even mention them.
Thanks for the Invite.
In debating dark matter particles versus modified gravity, I think that the pro-MOND side should raise the question of why there are no readily discernible dark matter halos around the Sun & the planet Jupiter.
In a pro-MOND versus anti-MOND debate, an anti-MOND advocate might ask: What is the new foundational paradigm that justifies MOND? Let us assume that gravitational energy is conserved. Given the preceding assumption, my guess is that MOND inertia explains MOND’s empirical successes.
Google “milgrom mond inertia”. What new physics might explain MOND inertia?
Hypothesis: The Higgs field continually emerges from string vibrations — this continual emergence creates 2 different forms of inertia: mass-energy inertia and MOND inertia.
“What is the new foundational paradigm that justifies MOND?”
Nobody knows (yet). It’s still just Nature sticking its middle finger in our smug faces. 🙂
As for string theory and associated crackpot handwaving,…
I say “show us the math”. I.e., publish the idea in a reputable peer-reviewed journal.
If MOND is inertial, that changes the way that we calculate mass. A MOND or Dark Matter halo about Jupiter would be manifest as a variance in the mass of Jupiter. The only mass determination of Jupiter is Newtonian via moon and probe orbital characteristics. There are so many harmonics in these calculations, I don’t think this is a productive place to search for an inertial field. (Not that I haven’t tried;)
Jupiter’s orbit is so far in the Newtonian regime that the usual approach to inferring its mass should be safe in MOND.
Didn’t even see this until after the panel met. Will there be video for us later?
Yes – I’m told there will be a recording on Youtube in a week or so. Will post it then.
what do you think is the source of the unexplained 511 keV line emission in the Galactic Center ?
Anomalous Ionization in the Central Molecular Zone by Sub-GeV Dark Matter
Pedro De la Torre Luque1,2,3,*, Shyam Balaji4,†, and Joseph Silk5,6,7,‡
Phys. Rev. Lett. 134, 101001 – Published 10 March, 2025
We demonstrate that the anomalous ionization rate observed in the Central Molecular Zone can be attributed to MeV dark matter annihilations into 𝑒+𝑒− pairs for galactic dark matter profiles with
:https://doi.org/10.1103/PhysRevLett.134.101001.
Not that.
It has been known for a long time that there is an electron-positron annihilation signal at the Galactic Center. That it could somehow be a decay product of dark matter is an idea that recurs every so often like a fizzled out comet: predictable in its return if disappointing in its apparition. There are any number of astrophysical processes that can do this. I’m old enough to remember a time when people would be embarrassed to make such a claim without first discounting all the obvious astrophysical sources. Somewhen in the 00’s that sociology flipped to claiming every obscure signal is DM just in case it works out so you can claim you were the first to discover it.
“If MOND is inertial, that changes the way we calculate mass.” Consider 3 conjectures:
(1) Milgrom is the Kepler of contemporary cosmology — on the basis of MOND’s (approximately) successful predictions.
(2) The main problem with string theory is that the string theorists fail to realize that Milgrom is the Kepler of contemporary cosmology.
(3) The foundations of physics needs a contemporary equivalent of a Newton or Einstein to explain MOND in terms of string theory.
Does string theory need one or more new symmetries and/or more than 11 dimensions?
Dodelson, Scott, Manoj Kaplinghat, and Ewan Stewart. “Solving the coincidence problem: Tracking oscillating energy.” Physical Review Letters 85, no. 25 (2000): 5276. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.85.5276
Note that in the 3rd edition of “Modern Cosmology” (2024) by Scott Dodelson & Fabian Schmidt, there is no mention of Milgrom or MOND.
https://books.google.com/books/about/Modern_Cosmology.html?id=TpUmEQAAQBAJ
Think of Green-Schwarz-Witten string theory as having 4 dimensions of spacetime, 6 dimensions of curled-up space, and 1 dimension of stringy uncertainty (needed to model the probability of a big bang occurring in flat space). Is there an extended model of string theory in which there are 11 “standard” dimensions plus 2 dimensions of curled-up time and 3 dimensions of curled-up MOND-inertia? Could a big bang occur in 3 possible time-directions with respect to 1 dimension of stringy uncertainty & with one dimension of MOND-inertia corresponding to each dimension of time?
David Merritt’s book “A Philosophical Approach to MOND” made a thorough review of cosmology texts and found that none mentioned the empirically established acceleration scale, let alone MOND.
Does string theory need a new stringy symmetry that explains MOND inertia? Consider the following hypothesis: For each 4-volume of spacetime near the Planck scale, there is a non-zero probability that nature will create a big bang within that particular 4-volume. In order to create a big bang, nature needs to overcome the MOND inertia that prevents big bangs from happening. If nature overcomes the fundamental MOND inertia then an inflaton field is generated. If nature does not overcome the fundamental MOND inertia then a negative pressure in the form of dark energy is generated. This hypothetical process is somehow described by a MOND inertial symmetry for string theory.
Symmetry at boundaries should be explored further as a way to describe observations in like dimensions. Complementary frames offer noncommensurate views of the same phenomenon, and there will be limitations to what is conserved in each view. There is something very interesting in this discussion of inertial observers that needs to be explored further.
https://iopscience.iop.org/article/10.1088/1367-2630/ab76f7
Dragan and Ekert summarize their work in the above linked text as,
“We argue that ruling out a superluminal family of observers from special relativity, regardless whether such observers exist or not, is not necessary; it leads to a classical description of a particle moving along a well-defined single trajectory. In contrast, if one keeps both subluminal and superluminal solutions then non-deterministic behavior and non-classical motion of particles arise as a natural consequence.
The superluminal solutions appear quite naturally in general relativity. For instance a Schwarzschild solution to Einstein equations written in Schwarzschild coordinates has a peculiar property that time and radial coordinates change their metric signs at the event horizon. This is normally dismissed by arbitrarily stating that the Schwarzschild solutions only make sense above the event horizon, although written in (freely falling) Kruskal coordinates, they are smooth at the horizon. In order to resolve this puzzle we point out that Schwarzschild coordinates correspond to stationary observers placed at fixed distances from the horizon. Such observers can be subluminal only above the horizon, and under the horizon they would require superluminal motions. The sign flip in the metric therefore signifies the transition from a subluminal to a superluminal family of stationary observers residing under the event horizon in a fixed distance from the singularity.
We believe that our approach is more than a mathematical exercise and, if taken seriously, it may offer new valuable insights into deep connections between quantum theory and special relativity.”