Why not sterile particles as dark matter?

In summary, the conversation covers the possibility of dark matter consisting of WIMPs or sterile particles, with the preference being WIMPs due to their prediction by SUSY. However, the idea of SUSY is considered to be failed by some experts. The possibility of sterile particles being created through gravitational processes in the early universe is also discussed, but it may not be consistent with current cosmological data. The issue of sterile neutrinos and their production is also addressed, with the conclusion being that they have a production problem and may not be a viable option for dark matter. Other potential candidates such as axions or ultra light scalars are mentioned, but they also have their own limitations.
  • #1
bcrowell
Staff Emeritus
Science Advisor
Insights Author
Gold Member
6,724
429
It seems that the most popular hypothesis is that dark matter consists of WIMPs. Can the existing data be described with sterile particles rather than ones that interact through the weak force? Is the only reason to prefer WIMPs that they are predicted by SUSY? (To me, as a nonspecialist, SUSY seems like a failed idea.)
 
Physics news on Phys.org
  • #2
If the particles are truly sterile, how were they produced?
 
  • Like
Likes nikkkom, Demystifier and bcrowell
  • #3
Vanadium 50 said:
If the particles are truly sterile, how were they produced?

Ah...that makes sense...

I guess one possibility is they could have been created by gravitational processes in the very early universe, but then I suppose that in order to match the current density of dark matter, we would have needed a high density at early times, which would not be consistent with cosmological data. Or we could imagine sufficiently energetic gravitational processes in the more recent past, but that seems unlikely.

Why do the above considerations not apply to sterile neutrinos, though? We can have neutrino oscillations to produce them, I guess...? I don't understand how this can be consistent with the observed solar neutrino flux.

Is it possible to make their electroweak charge very small (much less than for neutrinos or quarks), but not zero? I would think that their rate of production would then be very small, but their rate of annihilation would also be very small. Wouldn't that imply that their equilibrium concentration could be significant? Or is there some principle similar to quantization of electric charge that says you can't have an electroweak charge less than the standard unit?
 
  • #4
There are only two problems with sterile neutrinos: "sterile" and "neutrinos".

Absolutely sterile we covered. You're right that almost sterile might be made to work, depending on how almost is almost. Neutrinos have the additional problem that they move too fast to create the large scale structure we see. If you try and make the sterile neutrino heavy to fix that, its oscillation probability goes way, way down, so you don't make very many. (ueV things mix poorly with GeV things)
 
  • Like
Likes fresh_42 and bcrowell
  • #5
Vanadium 50 said:
If the particles are truly sterile, how were they produced?

would axions or ultra light scalar qualify as sterile?
 
  • #6
Vanadium 50 said:
There are only two problems with sterile neutrinos: "sterile" and "neutrinos".

Absolutely sterile we covered. You're right that almost sterile might be made to work, depending on how almost is almost. Neutrinos have the additional problem that they move too fast to create the large scale structure we see. If you try and make the sterile neutrino heavy to fix that, its oscillation probability goes way, way down, so you don't make very many. (ueV things mix poorly with GeV things)

Yea typically sterile neutrinos that are used for the purpose of creating dark matter have a significant production problem. Most of the methods (resonant production etc) found in the literature don't really work well from a model building point of view (they typically lead to conflicts with structure formation), but the method that is still viable is relatively low kev mass neutrinos produced via the decay of a heavy scalar. Often this is wrapped into the physics of the inflaton, but in principle it could come from many different larger embeddings.
 
  • Like
Likes mfb

1. Why can't sterile particles be dark matter?

Sterile particles, also known as neutrinos, are too light and too fast-moving to be considered dark matter. They do not interact with other particles enough to be the main component of dark matter.

2. Can sterile particles be a small part of dark matter?

While sterile particles are not the main component of dark matter, they could potentially make up a small fraction of it. However, current research suggests that they are not likely to contribute significantly to the overall mass of dark matter in the universe.

3. What other properties of dark matter rule out sterile particles?

Aside from being too light and fast-moving, sterile particles also do not have the clustering behavior that is observed in dark matter. This means they would not be able to form the large structures, such as galaxies and galaxy clusters, that are seen in the universe.

4. Are there any other candidates for dark matter besides sterile particles?

There are many other potential candidates for dark matter, including weakly interacting massive particles (WIMPs) and axions. Scientists are still actively researching and evaluating different possibilities for what dark matter could be.

5. How do scientists study and search for dark matter?

Scientists use a variety of techniques to study and search for dark matter, such as observing its effects on the rotation of galaxies, measuring the bending of light in gravitational lensing, and looking for signals from dark matter interactions in underground detectors. They also use computer simulations and theoretical models to better understand the properties and behavior of dark matter.

Similar threads

Replies
7
Views
2K
  • Beyond the Standard Models
Replies
2
Views
1K
  • Beyond the Standard Models
Replies
1
Views
1K
  • Beyond the Standard Models
8
Replies
264
Views
14K
  • Beyond the Standard Models
Replies
4
Views
2K
  • Beyond the Standard Models
Replies
10
Views
1K
  • Beyond the Standard Models
Replies
2
Views
2K
  • Beyond the Standard Models
Replies
11
Views
2K
  • Beyond the Standard Models
Replies
11
Views
2K
  • Beyond the Standard Models
Replies
1
Views
2K
Back
Top