Module

JacobsonSection.lean

Nyll.SchemeTheory.FiniteEtale.Algebra.JacobsonSection
1 declaration indexed from sourceView source ↗

Finite étale algebras with a quotient section

A finite étale algebra with a section over a Jacobson quotient is the base algebra if its reduction is generated by base scalars. The section makes the reduced scalar map injective, and finite étale conservativity lifts the resulting isomorphism to the original base.

Declarations

Algebra.FiniteEtale.bijective_algebraMap_of_quotientSection

A finite étale algebra is the base algebra if it has a section over a Jacobson quotient and every element of its reduction is a base scalar.

Source context 4 commands

Surrounding namespaces, section variables, and local commands at this declaration.

@[expose] public section
open scoped TensorProduct
universe u v
namespace Algebra.FiniteEtale
theorem bijective_algebraMap_of_quotientSection
    {R : Type u} {A : Type v} [CommRing R] [CommRing A] [Algebra R A]
    [Module.Finite R A] [Algebra.Etale R A]
    (I : Ideal R) (hI : I ≤ Ideal.jacobson ⊥) (σ : A →ₐ[R] R ⧸ I)
    (hsurj : Function.Surjective
      (algebraMap (R ⧸ I) (A ⧸ I.map (algebraMap R A)))) :
    Function.Bijective (algebraMap R A)