= Weak-decoupling temperature estimate
{title2=$T_d\sim[1.66\sqrt{g_*}/(G_F^2M_P)]^{1/3}$}
In <natural units> with unreduced <Planck mass> $M_P=G^{-1/2}$, the radiation-era <Hubble parameter> scales as $\sqrt{g_*}T^2/M_P$, while a low-energy <weak interaction> rate scales as $G_F^2T^5$. Their equality gives a decoupling scale of order one MeV. Distinct weak processes have distinct rate coefficients: <neutrino decoupling> and <cosmological weak freeze-out> of neutron-proton conversion are nearby events, not an identical precise temperature inferred from the power laws alone.
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