this post was submitted on 09 Jun 2024
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From forming bound states to normal scattering, many possibilities abound for matter-antimatter interactions. So why do they annihilate? There’s a quantum reason we simply can’t avoid.

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[–] neidu2@feddit.nl 14 points 5 months ago (18 children)

I'm a smoothbrain, so I like to think about it as them simply canceling each other out. What I'm more curious about though, is why there's so much matter compared to antimatter.

[–] macarthur_park@lemmy.world 23 points 5 months ago (6 children)

You’re not alone; matter-antimatter asymmetry is one of the big open questions in physics. Most particle processes treat matter and antimatter identically, but there are a few areas where matter and antimatter have slightly different interactions. These occurrences are violations of Charge Parity symmetry aka CP Violation.

There must have been a certain amount of CP violation during the early phases of the Big Bang to explain our matter-dominated universe. But the known amounts of CP Violation are nowhere near enough to explain the asymmetry in matter and antimatter. There are some proposed mechanisms that would violate CP symmetry in sufficient quantities, but these haven’t been experimentally observed. There are ongoing searches to detect these processes, or related processes that would be possible if these existed. Neutrinoless double beta decay searches are one example of these detection efforts.

In summary, there’s a guaranteed Nobel Prize to whoever can answer your question.

[–] drail@fedia.io 9 points 5 months ago

I work on a 0nuBB search doing detector R&D, this is spot on, but has 2 extra components. The three elements needed for explaining the asymmetry are:

  1. CP Violation
  2. Lepton or Baryon Number violation
  3. Interactions out of thermal equilibrium

These are the Sakharov conditions for Baryogenesis/Leptogenesis. #1 has been observed via the weak interaction but not in large enough quantities and is not observed via strong interactions, #2 is what proton decay and 0nuBB searches look for, and #3 can be, at least partially, explained by the expansion of the universe as a non-equilibrium interaction.

To get from leptogenesis to baryogenesis requires theretical physics I only barely understand using particles call sphaelerons that convert leptons to baryons.

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