Documentation

Mathlib.AlgebraicGeometry.Restrict

Restriction of Schemes and Morphisms #

Main definition #

Open subset of a scheme as a scheme.

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      The restriction of a scheme to an open subset.

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          The global sections of the restriction is isomorphic to the sections on the open set.

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              def AlgebraicGeometry.Scheme.Opens.stalkIso {X : Scheme} (U : X.Opens) (x : U) :
              (↑U).presheaf.stalk x X.presheaf.stalk x

              The stalks of an open subscheme are isomorphic to the stalks of the original scheme.

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                  theorem AlgebraicGeometry.Scheme.Opens.germ_stalkIso_hom {X : Scheme} (U : X.Opens) {V : (↑U).Opens} (x : U) (hx : x V) :
                  theorem AlgebraicGeometry.Scheme.Opens.germ_stalkIso_inv {X : Scheme} (U : X.Opens) (V : (↑U).Opens) (x : U) (hx : x V) :
                  def AlgebraicGeometry.Scheme.openCoverOfISupEqTop {s : Type u_1} (X : Scheme) (U : sX.Opens) (hU : ⨆ (i : s), U i = ) :

                  If U is a family of open sets that covers X, then X.restrict U forms an X.open_cover.

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                      theorem AlgebraicGeometry.Scheme.openCoverOfISupEqTop_map {s : Type u_1} (X : Scheme) (U : sX.Opens) (hU : ⨆ (i : s), U i = ) (i : s) :
                      (X.openCoverOfISupEqTop U hU).map i = (U i).ι
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                      theorem AlgebraicGeometry.Scheme.openCoverOfISupEqTop_obj {s : Type u_1} (X : Scheme) (U : sX.Opens) (hU : ⨆ (i : s), U i = ) (i : s) :
                      (X.openCoverOfISupEqTop U hU).obj i = (U i)
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                      theorem AlgebraicGeometry.Scheme.openCoverOfISupEqTop_J {s : Type u_1} (X : Scheme) (U : sX.Opens) (hU : ⨆ (i : s), U i = ) :
                      def AlgebraicGeometry.opensRestrict {X : Scheme} (U : X.Opens) :
                      (↑U).Opens { V : X.Opens // V U }

                      The open sets of an open subscheme corresponds to the open sets containing in the subset.

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                          theorem AlgebraicGeometry.coe_opensRestrict_apply_coe {X : Scheme} (U : X.Opens) (a✝ : (↑U).Opens) :
                          ((opensRestrict U) a✝) = (fun (a : U) => a) '' a✝
                          noncomputable def AlgebraicGeometry.Scheme.homOfLE (X : Scheme) {U V : X.Opens} (e : U V) :
                          U V

                          If U ≤ V, then U is also a subscheme of V.

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                              theorem AlgebraicGeometry.Scheme.homOfLE_homOfLE (X : Scheme) {U V W : X.Opens} (e₁ : U V) (e₂ : V W) :
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                              theorem AlgebraicGeometry.Scheme.homOfLE_apply {X : Scheme} {U V : X.Opens} (e : U V) (x : U) :
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                              theorem AlgebraicGeometry.Scheme.homOfLE_app {X : Scheme} {U V : X.Opens} (e : U V) (W : (↑V).Opens) :
                              def AlgebraicGeometry.Scheme.Opens.iSupOpenCover {J : Type u_1} {X : Scheme} (U : JX.Opens) :
                              (↑(⨆ (i : J), U i)).OpenCover

                              The open cover of ⋃ Vᵢ by Vᵢ.

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                                  The functor taking open subsets of X to open subschemes of X.

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                                      The functor that restricts to open subschemes and then takes global section is isomorphic to the structure sheaf.

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                                          X ∣_ U ∣_ V is isomorphic to X ∣_ V ∣_ U

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                                              noncomputable def AlgebraicGeometry.Scheme.Hom.isoImage {X Y : Scheme} (f : X.Hom Y) [IsOpenImmersion f] (U : X.Opens) :
                                              U (f.opensFunctor.obj U)

                                              If f : X ⟶ Y is an open immersion, then for any U : X.Opens, we have the isomorphism U ≅ f ''ᵁ U.

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                                                  If f : X ⟶ Y is an open immersion, then X is isomorphic to its image in Y.

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                                                      (⊤ : X.Opens) as a scheme is isomorphic to X.

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                                                          noncomputable def AlgebraicGeometry.Scheme.isoOfEq (X : Scheme) {U V : X.Opens} (e : U = V) :
                                                          U V

                                                          If U = V, then X ∣_ U is isomorphic to X ∣_ V.

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                                                              theorem AlgebraicGeometry.Scheme.isoOfEq_hom (X : Scheme) {U V : X.Opens} (e : U = V) :
                                                              (X.isoOfEq e).hom = X.homOfLE
                                                              theorem AlgebraicGeometry.Scheme.isoOfEq_inv (X : Scheme) {U V : X.Opens} (e : U = V) :
                                                              (X.isoOfEq e).inv = X.homOfLE

                                                              The restriction of an isomorphism onto an open set.

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                                                                  noncomputable def AlgebraicGeometry.Scheme.Opens.isoOfLE {X : Scheme} {U V : X.Opens} (hUV : U V) :

                                                                  If U ≤ V are opens of X, the restriction of U to V is isomorphic to U.

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                                                                      For f : R, D(f) as an open subscheme of Spec R is isomorphic to Spec R[1/f].

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                                                                          Given a morphism f : X ⟶ Y and an open set U ⊆ Y, we have X ×[Y] U ≅ X |_{f ⁻¹ U}

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                                                                              The restriction of a morphism X ⟶ Y onto X |_{f ⁻¹ U} ⟶ Y |_ U.

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                                                                                  the notation for restricting a morphism of scheme to an open subset of the target scheme

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                                                                                      theorem AlgebraicGeometry.isPullback_opens_inf_le {X : Scheme} {U V W : X.Opens} (hU : U W) (hV : V W) :

                                                                                      Restricting a morphism onto the image of an open immersion is isomorphic to the base change along the immersion.

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                                                                                          The restrictions onto two equal open sets are isomorphic. This currently has bad defeqs when unfolded, but it should not matter for now. Replace this definition if better defeqs are needed.

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                                                                                              Restricting a morphism twice is isomorphic to one restriction.

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                                                                                                  Restricting a morphism twice onto a basic open set is isomorphic to one restriction.

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                                                                                                      The stalk map of a restriction of a morphism is isomorphic to the stalk map of the original map.

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                                                                                                          def AlgebraicGeometry.Scheme.Hom.resLE {X Y : Scheme} (f : X.Hom Y) (U : Y.Opens) (V : X.Opens) (e : V (TopologicalSpace.Opens.map f.base).obj U) :
                                                                                                          V U

                                                                                                          The restriction of a morphism f : X ⟶ Y to open sets on the source and target.

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                                                                                                              theorem AlgebraicGeometry.Scheme.Hom.map_resLE {X Y : Scheme} (f : X Y) {U : Y.Opens} {V V' : X.Opens} (e : V (TopologicalSpace.Opens.map f.base).obj U) (i : V' V) :
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                                                                                                              theorem AlgebraicGeometry.Scheme.Hom.resLE_map {X Y : Scheme} (f : X Y) {U U' : Y.Opens} {V : X.Opens} (e : V (TopologicalSpace.Opens.map f.base).obj U) (i : U U') :
                                                                                                              theorem AlgebraicGeometry.Scheme.Hom.resLE_congr {X Y : Scheme} (f : X Y) {U U' : Y.Opens} {V V' : X.Opens} (e : V (TopologicalSpace.Opens.map f.base).obj U) (e₁ : U = U') (e₂ : V = V') (P : CategoryTheory.MorphismProperty Scheme) :
                                                                                                              P (resLE f U V e) P (resLE f U' V' )
                                                                                                              theorem AlgebraicGeometry.Scheme.Hom.resLE_appLE {X Y : Scheme} (f : X Y) {U : Y.Opens} {V : X.Opens} (e : V (TopologicalSpace.Opens.map f.base).obj U) (O : (↑U).Opens) (W : (↑V).Opens) (e' : W (TopologicalSpace.Opens.map (resLE f U V e).base).obj O) :
                                                                                                              appLE (resLE f U V e) O W e' = appLE f ((opensFunctor U.ι).obj O) ((opensFunctor V.ι).obj W)

                                                                                                              The stalk map of f.resLE U V at x : V is is the stalk map of f at x.

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                                                                                                                  f.resLE U V induces f.appLE U V on global sections.

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                                                                                                                      noncomputable def AlgebraicGeometry.Scheme.OpenCover.restrict {X : Scheme} (𝒰 : X.OpenCover) (U : X.Opens) :
                                                                                                                      (↑U).OpenCover

                                                                                                                      The restriction of an open cover to an open subset.

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                                                                                                                          theorem AlgebraicGeometry.Scheme.OpenCover.restrict_map {X : Scheme} (𝒰 : X.OpenCover) (U : X.Opens) (x✝ : 𝒰.J) :
                                                                                                                          (𝒰.restrict U).map x✝ = 𝒰.map x✝ ∣_ U
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                                                                                                                          theorem AlgebraicGeometry.Scheme.OpenCover.restrict_J {X : Scheme} (𝒰 : X.OpenCover) (U : X.Opens) :
                                                                                                                          (𝒰.restrict U).J = 𝒰.J
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                                                                                                                          theorem AlgebraicGeometry.Scheme.OpenCover.restrict_obj {X : Scheme} (𝒰 : X.OpenCover) (U : X.Opens) (x✝ : 𝒰.J) :
                                                                                                                          (𝒰.restrict U).obj x✝ = ((TopologicalSpace.Opens.map (𝒰.map x✝).base).obj U)