Modified Newtonian Dynamics + dark matter sterile neutrinos or PBH?

[kodama]

TL;DR Summary

Modified Newtonian Dynamics + dark matter

what about Modified Newtonian Dynamics + dark matter both right and both correct

Are sterile neutrinos consistent with clusters, the CMB and MOND?​

Garry W. Angus

If a single sterile neutrino exists such that mνs∼11eV, it can serendipitously solve all outstanding issues of the Modified Newtonian Dynamics. With it one can explain the dark matter of galaxy clusters without influencing individual galaxies, match the angular power spectrum of the cosmic microwave background and potentially fit the matter power spectrum. This model is flat with Ωνs∼0.23 and the usual baryonic and dark energy components, thus the Universe has the same expansion history as the $\lcdm$ model and only differs at the galactic scale where the Modified Dynamics outperforms $\lcdm$ significantly.

arXiv:0805.4014 [

If no sterile neutrinos then Modified Newtonian Dynamics + primordial black holes

Primordial Black Holes as Dark Matter: Recent Developments​

Bernard Carr1 and Florian Kühnel2· Cited by 280

Abstract​

Although the dark matter is usually assumed to be made up of some form of elementary particle, primordial black holes (PBHs) could also provide some of it. However, various constraints restrict the possible mass windows to 1016–1017 g, 1020–1024 g, and 10–103M⊙. The last possibility is contentious but of special interest in view of the recent detection of black hole mergers by LIGO/Virgo. PBHs might have important consequences and resolve various cosmological conundra even if they account for only a small fraction of the dark matter density. In particular, those larger than 103M⊙ could generate cosmological structures through the seed or Poisson effect, thereby alleviating some problems associated with the standard cold dark matter scenario, and sufficiently large PBHs might provide seeds for the supermassive black holes in galactic nuclei. More exotically, the Planck-mass relics of PBH evaporations or stupendously large black holes bigger than 1012M⊙ could provide an interesting dark component.

arXiv:2006.02838

 

[Ken G]

Glad to see work is still being done on alternative scenarios, science should always keep exploring the boundaries.

 

[ohwilleke]

The basic problem is finding any good reason for the sterile neutrinos or PBHs to be only in the places where MOND fails, and there is really no good theory that produces that result.

 

[Ken G]

I agree the problem with MOND has generally been the need to "shoehorn in" various aspects, where what you want is something that answers a lot of questions with only a small number of new ideas. Still, the discovery of very old galaxies might make it harder to get structure formation without some kind of help, perhaps from PBHs.

 

[ohwilleke]

I agree the problem with MOND has generally been the need to "shoehorn in" various aspects, where what you want is something that answers a lot of questions with only a small number of new ideas. Still, the discovery of very old galaxies might make it harder to get structure formation without some kind of help, perhaps from PBHs.

Very vanilla relativistic generalizations of MOND (and more generally and generically essentially any gravity based solution to dark matter phenomena) solve the problem of very old galaxies. This was predicted at least as early as 1997 (more than twenty-five years ago). There are gaps in toy model MOND, without a doubt, but early galaxy formation is not one of them.

 

[Ken G]

Ah, so you're saying that when dark matter is invoked to help explain structure formation, it is really just saying that anything that serves the same other purposes as dark matter is likely to also solve the structure issue. No matter how you slice it, we need more effect of gravity, one way or another.

 

[ohwilleke]

Ah, so you're saying that when dark matter is invoked to help explain structure formation, it is really just saying that anything that serves the same other purposes as dark matter is likely to also solve the structure issue. No matter how you slice it, we need more effect of gravity, one way or another.

You can get structure formation in basically two ways: more matter or more gravity. If you have more gravity instead of more matter, structure formation proceeds more quickly.

 

[Adrian59]

TL;DR Summary: Modified Newtonian Dynamics + dark matter

If no sterile neutrinos then Modified Newtonian Dynamics + primordial black holes

I don't know whether you have seen the results from MicroBooNE:

ref: 1) The MicroBoone Collaboration. (2021). 'Search for Neutrino-induced Neutral Current and Radiative Decayin MicroBooNE and a FirstTest of the MiniBooNE Low Energy Excess Under Single Photon Hypothesis'. ArXiv: 2110.00409v1,

and 2) The MicroBooNE Collaboration. (2022). 'Search for an Excess of Electron Neutrino in MicroBooNE Using Multiple Final State Topologies'. ArXiv: 2110.14054v3.

They did not see any excess signal up to about 2.5 GeV which of course is on the lower mass scale for the direct searches.