Question
Asked 26th Oct, 2017

Does Occam's razor favor MACHOs as candidates for Dark Matter?

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

Most recent answer

16th Mar, 2018
Salah A. Mabkhout
Thamar university
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
2 Recommendations

All Answers (4)

27th Oct, 2017
Kirk MacGregor
McPherson College
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.
2 Recommendations
30th Oct, 2017
George Dishman
Thales Group, UK
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?
2 Recommendations
16th Mar, 2018
Salah A. Mabkhout
Thamar university
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
2 Recommendations

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