English
Let R be a commutative semiring. If the pi-localization map toPiLocalization R is onto, then the prime spectrum of R is finite.
Русский
Пусть R — коммутативное полукольцо. Если отображение к локализации поPi сюрьективно, то множество спектра простых идеалов кольца R конечно.
LaTeX
$$$\\\\operatorname{Surjective}(\\\\operatorname{toPiLocalization}(R)) \\\\Rightarrow \\\\operatorname{Finite}(\\\\operatorname{PrimeSpectrum}(R))$$$
Lean4
theorem finite_of_toPiLocalization_surjective (surj : Function.Surjective (toPiLocalization R)) :
Finite (PrimeSpectrum R) :=
by
replace surj := (mapPiLocalization_bijective _ ⟨toPiLocalization_injective R, surj⟩).2.comp surj
rw [← RingHom.coe_comp, mapPiLocalization_naturality, RingHom.coe_comp] at surj
exact finite_of_toPiLocalization_pi_surjective surj.of_comp