Timeline for What gives mass to dark matter particles?
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| Jun 1, 2018 at 8:32 | comment | added | Luaan | @safesphere QFT doesn't need a reason for mass. Only the fields we know about require "a reason" for their mass (and that's only because of the weak interaction), but a massive particle that has no interactions with "our" matter (or even any other field) is perfectly consistent within QFT. Of course, just being consistent doesn't mean it's actually physical - but if it turns out dark matter doesn't interact weakly, it would be some evidence towards fields that are entirely invisible to us (except for gravity). And let's not forget that the Higgs boson is massive "without reason". | |
| May 31, 2018 at 19:21 | comment | added | Chris♦ | @safesphere A particle with no interactions at all is at least as unnatural, and if you posit a particle has no interactions, putting the mass in by hand is the only way for it to have mass. As for quantum gravity, the only honest answer is "nobody knows." Also, as an aside, I wouldn't say QFT works out easier for massless particles. Particles naturally acquire mass in a QFT. You can only have massless particles if there is some unbroken symmetry that protects the masslessness of the particle. | |
| May 31, 2018 at 17:10 | comment | added | safesphere | @Chris A mystery of nature is the existence of both massive and massless particles. QFT works out easier for massless, but needs a reason for the mass. It feels this reason must be fundamental. For example, the existence of a scalar field in the universe changing the nature of most, but not all particles. Like it or not, But it sounds fundamental. Now, adding mass by hand? Eh... It could technically work. Not sure how much of an insight it would bring. And if quantum gravity comes, would it be a gauge theory with a symmetry broken by the handmade mass? | |
| May 31, 2018 at 10:47 | comment | added | Luaan | @safesphere If you want a quick picture of what the interactions and particles would look like if the average value of the Higgs field were zero (it is thought that happens at extremely high energies, possibly during the very earliest time of our unvierse), profmattstrassler.com/articles-and-posts/… is a great summary. The site also has lots of deeper (though still very simple) explanations about the Standard Model and quantum physics in general. | |
| May 31, 2018 at 10:42 | comment | added | Luaan | @safesphere The Standard Model isn't a complete description of the universe. It just describes all the (non-gravitational) interactions between the quantum fields/particles you see around you. If dark matter doesn't interact with those fields/particles, it has nothing to do with the Standard Model. The reason the electron requires (something like) the Higgs field within SM is that it interacts weakly - and weak interaction breaks some pretty important symmetries. If you "take away" the Higgs, you get two "electron" fields - one of which is weakly interacting, and the other isn't. | |
| May 30, 2018 at 19:38 | history | edited | Chris♦ | CC BY-SA 4.0 |
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| May 30, 2018 at 19:06 | comment | added | Chris♦ | @safesphere If it has no interactions at all, there's no contradictions to just give it a mass "by hand" in the Lagrangian, since it doesn't interact with any gauge fields and so a mass term does not break gauge symmetry. | |
| May 30, 2018 at 18:30 | comment | added | safesphere | My question is specifically about the dark matter that interacts only gravitationally. Thus the hidden sector and all other interactions are excluded. Sorry, but you seem to be answering a more generic question than mine. There are no known ways in the Standard Model that I am aware of for only gravitationally interacting dark matter to acquire mass. | |
| May 30, 2018 at 18:24 | history | answered | Chris♦ | CC BY-SA 4.0 |