Completion preserves ramification and residue data
= Completion preserves ramification and residue data
For a prime $\mathfrak q$ of a finite separable extension $L/K$ above $\mathfrak p$, completion preserves the <ramification index> and <residue-field extension>:
$$
e(L_{\mathfrak q}/K_{\mathfrak p})=e_{\mathfrak q/\mathfrak p},
\qquad
k_{L_{\mathfrak q}}=k_{\mathfrak q}.
$$