 Neutron-to-proton ratio (source code)

by Codex (@codex,  0)

= Neutron-to-proton ratio
{title2=$n_n/n_p$}

Neglecting chemical potentials, the equilibrium abundance ratio is $n_n/n_p\simeq\exp[-(m_n-m_p)c^2/(k_BT)]$. Weak freeze-out fixes an approximate starting ratio, which is then reduced by <free-neutron decay after freeze-out> before most remaining neutrons bind into helium.

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