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DerivedAlgGeo.AlgebraicGeometry.Surface.Enriques.PaperExtension

Mutation, curve chains, Ext computations, and extension for the Enriques papers #

This is the geometric adapter for the next layer of arXiv:1912.04332v2 and arXiv:2104.13610v2.

The remaining geometric gaps stay visible. The current Cartier-divisor API has no predicate saying that an effective divisor is an irreducible curve, and PaperCurveChainData still supplies residual orthogonality of each curve quotient. It no longer supplies the triangles themselves. Likewise, the abstract dg cone and its pointwise transform triangle are now functorial, with DGFunctor.HomogeneousNatTrans.ConeData as the construction root and FourierMukai.CounitKernelConeData as the adjunction-counit specialization. Constructing the paper's extended Fourier--Mukai kernel still waits on the geometric H⁰ model, the paper's ordinary kernel morphism with its exact counit-transform equation, an enhancement, and exactness of kernel evaluation (#853--#855); it is not silently identified with the counit specialization. Its categorical consequences continue to use the existing kernel/adjunction roots immediately.

Projection existence and mutation triangles #

The geometric admissibility input for the residual component.

The papers obtain this from an admissible semiorthogonal decomposition. It is kept supplied here because the current Enriques construction proves only that the residual right orthogonal is triangulated.

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    The paper's objectwise mutation triangle

    S_i ⟶ L_{i1} ⟶ L_{\mathcal K}(L_{i1}).

    The first term is definitionally the residual projection object and the first map is its adjunction counit.

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      (-2)-curve chains #

      A supplied A_n chain of effective Cartier divisors with the numerical intersection matrix of (-2)-curves.

      Effectivity and the intersection matrix are genuine repository notions. Irreducibility/reducedness are not yet expressible, so the word "curve" in the declaration name records the intended geometric realization rather than an unavailable extra predicate.

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        The sum of the first j divisors in the chain.

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          The source divisor in the normalized sequence for the next curve is the preceding prefix.

          The canonical bounded-derived triangle for one step of the divisor chain, after tensoring by an arbitrary base line bundle. Its first two vertices are L ⊗ O(prefix j) and L ⊗ O(prefix (j+1)).

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            The geometric data behind a block decomposition in Paper II, Proposition 1.4 and Lemma 1.9.

            memberClass is the formula L_{ij} = L_{i1} ⊗ O(R_{i1}+⋯+R_{i,j-1}) in the Picard group. The Picard formula proves that each supplied line-bundle representative is isomorphic to the corresponding tensor product by O(prefix j); the adapter chooses such isomorphisms. The divisor-derived triangle is therefore constructed below rather than stored. Only residual orthogonality of its quotient remains supplied.

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              The Picard-class formula chooses an isomorphism from each selected bundle to the first bundle tensored by the corresponding Cartier prefix.

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                Identify a block member with its canonical tensor-by-prefix derived object, combining the block presentation and the Picard-class formula.

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                  The canonical divisor-derived triangle underlying the j-th step of a paper block.

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                    Identify the source of the canonical step triangle with the j-th block member.

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                      Identify the target of the canonical step triangle with the next block member.

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                        The canonical divisor triangle transported to the paper's chosen block representatives. Its first morphism is the required successive block map.

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                          Canonical comparison from the divisor step triangle to its transport onto the selected block representatives.

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                            Construct the complete projection-chain triangle data from Cartier sequences, Picard-class identifications, and the supplied quotient orthogonality.

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                              Paper II, Remark 2.3(ii): every member of a block has the same residual projection as its first member.

                              Unlike the earlier supplied statement seam, this is proved from the successive divisor triangles and their residual-orthogonality.

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                                Ext computations and classification constructors #

                                Paper I's Ext computations for the ten projected objects, separated from their Serre-shift identifications and the completeness argument.

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                                  theorem AlgebraicGeometry.EnriquesSurface.IsotropicCollection.PaperIProjectionExtData.toProjectionClassificationData {k : Type u} [Field k] {Y : Scheme} [Y.Over (Spec (CommRingCat.of k))] [IsSmoothProperVariety k Y] {C : SmoothProperVariety.CanonicalSheafData k Y 2} [SmoothProperVariety.IsEnriquesSurface k Y C] {D : Cohomology.FiniteCohomology k Y} {S : D.LinearConnectingSystem} {T : IsotropicCollection D S} {exceptional : T.ExceptionalityData} {semiorthogonal : T.SemiorthogonalityData} {P : T.PaperCategoryData exceptional semiorthogonal} {B : T.PaperBlockData exceptional semiorthogonal (Fin 10)} {Q : T.PaperResidualProjectionData exceptional semiorthogonal} (A : T.PaperIProjectionExtData B Q) (singleton : ∀ (i : Fin 10), B.blocks.length i = 1) (serreShift : ∀ (i : Fin 10), Nonempty (P.residualSerre.serre.S.obj (B.projectedObject Q i) ≅ (CategoryTheory.shiftFunctor (T.ResidualCategory exceptional semiorthogonal) 3).obj (B.projectedObject Q i))) (complete : ∀ (E : T.ResidualCategory exceptional semiorthogonal), CategoryTheory.SerreFunctor.IsSphericalObject P.residualSerre.serre 3 E ↔ ∃ (i : Fin 10), CategoryTheory.SerreFunctor.IsShiftOf E (B.projectedObject Q i)) :

                                  Assemble Paper I's projection classification package from the Ext calculation, the Serre action, and the remaining completeness theorem.

                                  structure AlgebraicGeometry.EnriquesSurface.IsotropicCollection.PaperIIProjectionExtData {k : Type u} [Field k] {Y : Scheme} [Y.Over (Spec (CommRingCat.of k))] [IsSmoothProperVariety k Y] {C : SmoothProperVariety.CanonicalSheafData k Y 2} [SmoothProperVariety.IsEnriquesSurface k Y C] {D : Cohomology.FiniteCohomology k Y} {S : D.LinearConnectingSystem} (T : IsotropicCollection D S) {exceptional : T.ExceptionalityData} {semiorthogonal : T.SemiorthogonalityData} (P : T.PaperCategoryData exceptional semiorthogonal) {I : Type t} [Fintype I] (B : T.PaperBlockData exceptional semiorthogonal I) (Q : T.PaperResidualProjectionData exceptional semiorthogonal) :

                                  Paper II's block-sensitive self-Ext and cross-Ext computations.

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                                    The Ext and Serre computations make a singleton projection spherical.

                                    The Ext and Serre computations make a longer-block projection pseudoprojective.

                                    Assemble Paper II's full classification package after supplying only the two global completeness statements.

                                    Fourier--Mukai extension between two Enriques surfaces #

                                    @[reducible, inline]
                                    abbrev AlgebraicGeometry.EnriquesSurface.IsotropicCollection.PaperResidualKernelEquivalence {k : Type u} [Field k] {Y₁ Y₂ : Scheme} [Y₁.Over (Spec (CommRingCat.of k))] [Y₂.Over (Spec (CommRingCat.of k))] [IsSmoothProperVariety k Y₁] [IsSmoothProperVariety k Y₂] {C₁ : SmoothProperVariety.CanonicalSheafData k Y₁ 2} {C₂ : SmoothProperVariety.CanonicalSheafData k Y₂ 2} [SmoothProperVariety.IsEnriquesSurface k Y₁ C₁] [SmoothProperVariety.IsEnriquesSurface k Y₂ C₂] {D₁ : Cohomology.FiniteCohomology k Y₁} {D₂ : Cohomology.FiniteCohomology k Y₂} {S₁ : D₁.LinearConnectingSystem} {S₂ : D₂.LinearConnectingSystem} (T₁ : IsotropicCollection D₁ S₁) (T₂ : IsotropicCollection D₂ S₂) {exceptional₁ : T₁.ExceptionalityData} {exceptional₂ : T₂.ExceptionalityData} {semiorthogonal₁ : T₁.SemiorthogonalityData} {semiorthogonal₂ : T₂.SemiorthogonalityData} {I J : Type t} [Fintype I] [Fintype J] (B₁ : T₁.PaperBlockData exceptional₁ semiorthogonal₁ I) (B₂ : T₂.PaperBlockData exceptional₂ semiorthogonal₂ J) {W : Type u} [CategoryTheory.Category.{u_1, u} W] (corr : CategoryTheory.Triangulated.FourierMukai.Correspondence (DerivedCat Y₁) (DerivedCat Y₂) W) :
                                    Type (u + 1)

                                    A Fourier--Mukai-type equivalence between the residual categories of two Enriques block decompositions. The block residuals are identified with the previously constructed neutral residual components by PaperBlockData.residual_eq.

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                                      @[reducible, inline]
                                      abbrev AlgebraicGeometry.EnriquesSurface.IsotropicCollection.PaperExceptionalBlockExtensionData {k : Type u} [Field k] {Y₁ Y₂ : Scheme} [Y₁.Over (Spec (CommRingCat.of k))] [Y₂.Over (Spec (CommRingCat.of k))] [IsSmoothProperVariety k Y₁] [IsSmoothProperVariety k Y₂] {C₁ : SmoothProperVariety.CanonicalSheafData k Y₁ 2} {C₂ : SmoothProperVariety.CanonicalSheafData k Y₂ 2} [SmoothProperVariety.IsEnriquesSurface k Y₁ C₁] [SmoothProperVariety.IsEnriquesSurface k Y₂ C₂] {D₁ : Cohomology.FiniteCohomology k Y₁} {D₂ : Cohomology.FiniteCohomology k Y₂} {S₁ : D₁.LinearConnectingSystem} {S₂ : D₂.LinearConnectingSystem} (T₁ : IsotropicCollection D₁ S₁) (T₂ : IsotropicCollection D₂ S₂) {exceptional₁ : T₁.ExceptionalityData} {exceptional₂ : T₂.ExceptionalityData} {semiorthogonal₁ : T₁.SemiorthogonalityData} {semiorthogonal₂ : T₂.SemiorthogonalityData} {I J : Type t} [Fintype I] [Fintype J] (B₁ : T₁.PaperBlockData exceptional₁ semiorthogonal₁ I) (B₂ : T₂.PaperBlockData exceptional₂ semiorthogonal₂ J) {W W' : Type u} [CategoryTheory.Category.{u_1, u} W] [CategoryTheory.Category.{u_2, u} W'] (corr : CategoryTheory.Triangulated.FourierMukai.Correspondence (DerivedCat Y₁) (DerivedCat Y₂) W) (corr' : CategoryTheory.Triangulated.FourierMukai.Correspondence (DerivedCat Y₂) (DerivedCat Y₁) W') (R : T₁.PaperResidualKernelEquivalence T₂ B₁ B₂ corr) :
                                      Type (max (max (max t (u + 1)) u) (u + 1))

                                      The conclusion of the papers' finite extension argument, specialized to the exceptional blocks of two Enriques surfaces. Its ambientEquivalence is the promoted equivalence of ambient derived categories, and its objectIso uses one common shift on every member of a block.

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