English
The valuation on hat K is surjective iff the valuation on K is surjective.
Русский
Оценка на hat K сюръективна тогда и только тогда, когда оценка на K сюръективна.
LaTeX
$$$Function.Surjective(v: hat{K} \to Γ_0) \;\Leftrightarrow\; Function.Surjective(v: K \to Γ_0)$$$
Lean4
noncomputable instance valuedCompletion : Valued (hat K) Γ₀
where
v := extensionValuation
is_topological_valuation
s :=
by
suffices HasBasis (𝓝 (0 : hat K)) (fun _ => True) fun γ : Γ₀ˣ => {x | extensionValuation x < γ}
by
rw [this.mem_iff]
exact exists_congr fun γ => by simp
simp_rw [← closure_coe_completion_v_lt]
exact (hasBasis_nhds_zero K Γ₀).hasBasis_of_isDenseInducing Completion.isDenseInducing_coe