Dear All,
not only in our university, but almost in all well known to me lectures about Dark Matter, MACHOs (Massive Astrophysical Compact Halo Objects) are rather incidentally discussed while candidates as WIMPs, Axions or Sterile Neutrinos dominate the talks.
Is this - with nowadays knowledge and theoretical assumptions - justified?
With the description of a great abundance of primordial black holes MACHOs do serve a hypothetical answer for almost any questions like rotation curves, radial velocitiy, intermediate black holes, missing-satellite-problem, too-big-to-fail-problem, ...
Of course it is a highly speculative topic. BUT the WIMPs are too (if not even more). So shouldn't we - in accordance with the Principle of Occam's razor - favor MACHOs instead, because they are able to solve a lot of problems at once and at the same time we don't need to extend the Standard Model for introducing them?
Why do WIMPs and particle-like entities dominate? Did i miss a hint (for example some fundamental advantages of this models?). Or is it a general problem ultimately based on ignorance to a great extent?
Thank you
I agree with you that Occam's Razor privileges MACHOs as candidates for dark matter over WIMPs. The fact that MACHOs are compatible with the standard model seems to be an extremely strong point in their favor.
The best way to assess the possibility would be to start by surveying the observational evidence for dark matter and consider what fits all the resulting constraints. For example how would MACHOs as dark matter explain the evidence from primordial deuterium abundance?
"Or is it a general problem ultimately based on ignorance to a great extent?"
Yes it is:
- the virial theorem is wrongly applied, hence the "expected" velocity curves are wrongly calculated.
- gravitomagnetism, as confirmed by the Gravity Probe B experiment, allows to consider that angular momentum of a galaxy's spinning center is transmitted by gravity to all the orbits of the galaxy, making them swivel towards the equitorial plane. This is the same as the auto-reorientation of EM-solenoids in a given magnetic field.
- This transmission of angular moment gives a North-South pressure on the formed disc, ~1/R2 from the center.
- the problem of the deuterium abundance is due to the fact that a mass density treshold is necessary before one can get visible star formation. Further from the center, no star formation is seen because of ~1/R2 for the N-S pressure, but then, deuterium is abundant.
- when starting with a plausible mass distribution of a spherical galaxy, the obtained Newtonion integration of masses in the newly formed disc galaxy (after the swiveling of the orbits) results in the correct velocity curves.
Article Erroneous Use of the Virial Theorem for Elliptical-and Disc ...
Research Deduction of orbital velocities in disk galaxies. “Dark Matt...
No
MACHOs are dead: Decades of research have narrowed down the possibilities. Early favourites included not only black holes, but also other massive compact halo objects (MACHOs) made of ordinary matter. Brown dwarfs won't account for all of the so-called dark matter. A series of studies, however, gradually ruled out most of the possibilities. For example, researchers determined that black holes between about one-thousand billionth and one-billionth the mass of the Sun would destroy neutron stars. The presence of neutron stars in ancient globular clusters therefore suggests that primordial black holes of this size are extremely rare and could not account for all the dark matter in the Universe. Bird's theory was based on the fact that no one had yet ruled out larger black holes. But in the view of theoretical physicist John Ellis of King's College London, “MACHOs are dead.
According to the Criteria for scientific method and Occam's razor:
Criteria for scientific method:
(i). The model must fit the data and agree with observations.
(ii). The model must make predictions that allow it to be tested (falsifiable).
(iii). The model should be aesthetically pleasing
(Occam's razor: "If you have two theories that both explain the observed facts, then you should use the simplest with the fewest assumptions).
Dark Matter is an additional assumption. It would be better if we explained the flat rotation curve without invoking Dark Matter.
See: The Hyperbolic Universe Does Not Need Dark Matter
https://www.researchgate.net/publication/322490801_The_Hyperbolic_Universe_Does_Not_Need_Dark_Matter
Preprint The Modified Big Bang Theory
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