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The Evidence is Building that Dark Matter is Made of Axions
(www.universetoday.com)
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this post was submitted on 20 Jun 2023
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Some context on axions.
For decades scientists noticed that quantum phenomena respect something called CP-symmetry, that is a really posh way to say "if you sub your particle with an antiparticle and invert its spatial coordinates, the laws of physics will stay the same". So for example it doesn't really matter if you have an electron at (1,1,1) or a positron at (-1,-1,-1), the effect is the same.
There are some exceptions (called CP violations) but for most part CP-symmetry is a real phenomenon. And one of those violations that could happen is when you're dealing with quarks (the junk that protons and neutrons are composed of). And if something can happen, in quantum mechanics, it will happen. So why don't CP violations happen?
Based on that, in 1977 Roberto Peccei and Helen Quinn predicted a new particle, that they named "axion" after some laundry detergent, as "it washed off the problem" (yup - scientists being silly with names, nothing new). That axion particle would be a really small particle, but with mass (unlike photons), and it compensates the predicted CP violation.
Now, to the link: apparently axions are a real thing, and they explain (at least partially) what dark matter is supposed to be.
Thank you for the thoughtful response, as I was genuinely interested to know what axion was.
As a side note, I remember reading about CP violations a while back (scientists love to use the metaphor of "how to distinguish left from right" to explaining those) and they were saying that CPT symmetry was inviolable, but they did also thought the same about Charge (C), Parity (P) and Time (T) before. Do you think we will ever see a CPT violation?
I don't think that we will, but people are still looking for it, albeit indirectly, and focusing on special relativity. Stuff like "are the photons still obeying Lorenz symmetry here? What about there? And there?". (Note: Lorenz symmetry violations would imply CPT violations.)