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Mathlib.AlgebraicGeometry.Modules.Sheaf

The category of sheaves of modules over a scheme #

In this file, we define the abelian category of sheaves of modules X.Modules over a scheme X, and study its basic functoriality.

The category of sheaves of modules over a scheme.

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    Morphisms between 𝒪ₓ-modules. Use Hom.app to act on sections.

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      The forgetful functor from 𝒪ₓ-modules to presheaves of modules. This is mostly useful to transport results from (pre)sheaves of modules to 𝒪ₓ-modules and usually shouldn't be used directly when working with actual 𝒪ₓ-modules.

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        The forgetful functor from 𝒪ₓ-modules to presheaves of modules is fully faithful.

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          The forgetful functor from 𝒪ₓ-modules to presheaves of abelian groups.

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            The underlying abelian presheaf of an 𝒪ₓ-module.

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              Notation for sections of a presheaf of module.

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                noncomputable def AlgebraicGeometry.Scheme.Modules.Hom.mapPresheaf {X : Scheme} {M N : X.Modules} (φ : M N) :

                The underlying map between abelian presheaves of a morphism of 𝒪ₓ-modules.

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                  The application of a morphism of 𝒪ₓ-modules to sections.

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                    @[simp]
                    theorem AlgebraicGeometry.Scheme.Modules.Hom.app_smul {X : Scheme} {M N : X.Modules} {U : X.Opens} (φ : M N) (r : (X.presheaf.obj (Opposite.op U))) (x : (M.presheaf.obj (Opposite.op U))) :
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                    theorem AlgebraicGeometry.Scheme.Modules.Hom.add_app {X : Scheme} {M N : X.Modules} {U : X.Opens} (φ ψ : M N) :
                    app (φ + ψ) U = app φ U + app ψ U
                    @[simp]
                    theorem AlgebraicGeometry.Scheme.Modules.Hom.sub_app {X : Scheme} {M N : X.Modules} {U : X.Opens} (φ ψ : M N) :
                    app (φ - ψ) U = app φ U - app ψ U
                    theorem AlgebraicGeometry.Scheme.Modules.hom_ext {X : Scheme} {M N : X.Modules} (f g : M N) (H : ∀ (U : X.Opens), Hom.app f U = Hom.app g U) :
                    f = g
                    theorem AlgebraicGeometry.Scheme.Modules.hom_ext_iff {X : Scheme} {M N : X.Modules} {f g : M N} :
                    f = g ∀ (U : X.Opens), Hom.app f U = Hom.app g U

                    The pushforward functor for categories of sheaves of modules over schemes.

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                      The pullback functor for categories of sheaves of modules over schemes.

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                        The pullback functor for categories of sheaves of modules over schemes is left adjoint to the pushforward functor.

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                          The pushforward of sheaves of modules by the identity morphism identifies to the identity functor.

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                            The pullback of sheaves of modules by the identity morphism identifies to the identity functor.

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                              The composition of two pushforward functors for sheaves of modules on schemes identify to the pushforward for the composition.

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                                The composition of two pullback functors for sheaves of modules on schemes identify to the pullback for the composition.

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                                  noncomputable def AlgebraicGeometry.Scheme.Modules.pushforwardCongr {X Y : Scheme} {f g : X Y} (hf : f = g) :

                                  Pushforwards along equal morphisms are isomorphic.

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                                    noncomputable def AlgebraicGeometry.Scheme.Modules.pullbackCongr {X Y : Scheme} {f g : X Y} (hf : f = g) :

                                    Inverse images along equal morphisms are isomorphic.

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                                      The pseudofunctor from Schemeᵒᵖ to the bicategory of adjunctions which sends a scheme X to the category X.Modules of sheaves of modules over X. (This contains both the covariant and the contravariant functorialities of these categories.)

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                                        Restriction of an 𝒪ₓ-module along an open immersion. This is isomorphic to the pullback functor (see restrictFunctorIsoPullback) but has better defeqs.

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                                          @[reducible, inline]
                                          noncomputable abbrev AlgebraicGeometry.Scheme.Modules.restrict {X Y : Scheme} (M : Y.Modules) (f : X Y) [IsOpenImmersion f] :

                                          The restriction of a module along an open immersion.

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                                            The restriction of a module along an open immersion.

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                                              Restriction is right adjoint to pushforward.

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                                                Restriction is naturally isomorphic to the inverse image.

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                                                  Restriction along the identity is isomorphic to the identity.

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                                                    Restriction along the composition is isomorphic to the composition of restrictions.

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                                                      Restriction along equal morphisms are isomorphic.

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                                                        Restriction along open immersions commutes with taking stalks.

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