Module

ImageSubmoduleRestriction.lean

Nyll.SchemeTheory.Modules.ImageSubmoduleRestriction
2 declarations indexed from sourceView source ↗

The actual image on an open where its source generates

If a morphism into a prescribed native submodule becomes epimorphic on an open, the image of its composite into the ambient sheaf restricts to that exact prescribed submodule. The reverse inclusion is constructed by the epimorphism--monomorphism lifting property in the actual sheaf category.

Imports5
Imported by2

Declarations

SheafOfModules.overSheafIso_inv_ι
Source context 5 commands

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

noncomputable section
universe u v
open CategoryTheory
namespace SheafOfModules
variable {C : Type u} [Category.{v} C] {J : GrothendieckTopology C}
  {R : Sheaf J RingCat.{u}}
theorem overSheafIso_inv_ι {M : SheafOfModules.{u} R}
    (N : M.Submodule) (U : C) :
    (Submodule.overSheafIso N U).inv ≫ (N.over U).ι = N.ι.over U
SheafOfModules.imageSubmodule_over_eq_of_epi

An actual local epimorphism onto P gives literal equality between P and the restriction of its image in the ambient sheaf.

Source context 6 commands

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

noncomputable section
universe u v
open CategoryTheory
namespace SheafOfModules
variable {C : Type u} [Category.{v} C] {J : GrothendieckTopology C}
  {R : Sheaf J RingCat.{u}}
variable [HasSheafify J AddCommGrpCat.{u}] [J.WEqualsLocallyBijective AddCommGrpCat.{u}]
  [∀ U : C, HasSheafify (J.over U) AddCommGrpCat.{u}]
  [∀ U : C, (J.over U).WEqualsLocallyBijective AddCommGrpCat.{u}]
theorem imageSubmodule_over_eq_of_epi {A M : SheafOfModules.{u} R}
    (P : M.Submodule) (f : A ⟶ P.toSheafOfModules) (U : C) [Epi (f.over U)] :
    (imageSubmodule (f ≫ P.ι)).over U = P.over U