Retrieving "Grand Unification Theory" from the archives

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1. Peccei Quinn Theory

   Linked via "grand unification"

   $$ ma \propto \frac{f{\pi} m{\pi} \sqrt{z}}{Fa} $$
   where $f{\pi}$ and $m{\pi}$ are the pion decay constant and mass, respectively, and $z$ is a dimensionless factor representing the ratio of up and down quark masses. Theoretical estimations place the expected value of ${F_a}$ to be near the scale of grand unification, often around $10^{12}$ GeV, which implies an axion mass in the range of $10^{-6}$ to $10^{-3}$ eV [4].
   Axions interact primarily with photons via a term in t…

2. Weak Isospin

   Linked via "grand unification"

   The term "isospin" was first introduced by Heisenberg in the context of nucleon-pion interactions, where the proton and neutron were viewed as two states of the same particle, the nucleon, with $I=1/2$. While this strong interaction analogy is useful, the weak isospin formulation is distinctly tied to the left-handed chirality) of the weak force, contrasting sharply with the strong force’s treatment …