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Symmetry between up and down quarks is more broken than expected

(phys.org)
87 points terminalbraid | 3 comments | 29 Mar 25 10:12 UTC | HN request time: 0.639s | source
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ars ◴[31 Mar 25 15:54 UTC] No.43536434[source]▶
BTW isospin is actually how many up vs down quarks they are. It's not a fundamental property like spin or charge.

It's an old term that was created before they knew that up and down quarks existed.

Personally I find the term outdated because there are 4 other quarks, and isospin only talks about two of them.

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1. floxy ◴[31 Mar 25 16:45 UTC] No.43537038[source]▶
https://www.youtube.com/watch?v=esayi49OAk4
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2. ars ◴[31 Mar 25 23:01 UTC] No.43540938[source]▶
This video just drive home that using isospin and hypercharge is like using epicycles to describe the motion of the planets: It works, but it's overly complicated, and it's better to just use the actual thing (quarks, and heliocentrism).
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3. pdonis ◴[01 Apr 25 02:49 UTC] No.43542315[source]▶
> using isospin and hypercharge is like using epicycles to describe the motion of the planets

No, it isn't; those are actual quantum numbers of the electroweak interaction below the symmetry breaking energy (the other such quantum number is electric charge).