Module

QuasicoherentCokernel.lean

Nyll.SchemeTheory.Modules.QuasicoherentCokernel
3 declarations indexed from sourceView source ↗

Quasicoherence of actual cokernels

On an affine scheme, the actual morphism is transported through its canonical tilde isomorphisms. The existing tilde adjunction preserves its cokernel. Restriction and the shared affine-presentation criterion then give the result on arbitrary schemes.

Imports5
Imported by3

Declarations

AlgebraicGeometry.Scheme.Modules.affineTildeIso
Source context 4 commands

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

noncomputable section
universe u
open CategoryTheory Limits
namespace AlgebraicGeometry.Scheme.Modules
def affineTildeIso {R : CommRingCat.{u}}
    (M : (Spec R).Modules) [M.IsQuasicoherent] :
    (tilde.functor R).obj ((moduleSpecΓFunctor (R := R)).obj M) ≅ M
AlgebraicGeometry.Scheme.Modules.isQuasicoherent_cokernel_toSpec

The actual cokernel of a morphism between quasicoherent modules on an affine scheme is quasicoherent.

Source context 4 commands

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

noncomputable section
universe u
open CategoryTheory Limits
namespace AlgebraicGeometry.Scheme.Modules
theorem isQuasicoherent_cokernel_toSpec
    {R : CommRingCat.{u}} {M N : (Spec R).Modules}
    [M.IsQuasicoherent] [N.IsQuasicoherent] (φ : M ⟶ N) :
    (cokernel φ).IsQuasicoherent
AlgebraicGeometry.Scheme.Modules.isQuasicoherent_cokernel

The actual categorical cokernel of a morphism between quasicoherent modules on any scheme is quasicoherent.

Source context 4 commands

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

noncomputable section
universe u
open CategoryTheory Limits
namespace AlgebraicGeometry.Scheme.Modules
theorem isQuasicoherent_cokernel
    {X : Scheme.{u}} {M N : X.Modules}
    [M.IsQuasicoherent] [N.IsQuasicoherent] (φ : M ⟶ N) :
    (cokernel φ).IsQuasicoherent