English
For a prime p and an algebraically closed field k, the ring k has the structure of a PerfectRing k p.
Русский
При простом p и алгебраически замкнутом поле k кольцо k имеет структуру PerfectRing k p.
LaTeX
$$$\forall (k) [\mathrm{Field\;k}] [\mathrm{Fact}\;\mathrm{p.Prime}] [\mathrm{CharP}\;k\;p] [IsAlgClosed k],\; PerfectRing k p$$$
Lean4
noncomputable instance (priority := 100) perfectField [IsAlgClosed k] : PerfectField k :=
by
obtain _ | ⟨p, _, _⟩ := CharP.exists' k
exacts [.ofCharZero, PerfectRing.toPerfectField k p]