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DerivedAlgGeo.CategoryTheory.Triangulated.FourierMukai.DGAdjunctionTwistComparison

Comparing presented dg and Fourier--Mukai twists #

Suppose a strict dg adjunction is presented on ordinary categories by a pair of Fourier--Mukai transforms. A chosen dg cone on its counit and an independently chosen enhanced Fourier--Mukai cone then give two pointwise distinguished counit triangles with the same first two vertices and the same first map.

Mathlib's isoTriangleOfIso₁₂ supplies a noncanonical isomorphism between the two triangles at each target object. Its third component compares the ordinary transport of the actual dg twist with the Fourier--Mukai twist.

The unconditional completion is chosen separately at each object and therefore supplies no naturality. A separate PresentedCounitComparisonData interface records a genuinely supplied natural twist isomorphism and its two remaining triangle squares; from that input the file constructs the natural counit-triangle isomorphism. It does not construct this input or prove independence of either cone choice. Under an explicit equivalence hypothesis on the dg twist at H⁰, the comparison packages the selected kernel as a KernelAutoequivalence; it does not prove that hypothesis or sphericality. A further ShiftCompatibility refinement can select a Fourier--Mukai CommShift structure compatible with the comparison; exactness then transfers through Mathlib's existing Functor.isTriangulated_of_iso theorem.

At each target object, the presented dg counit triangle is noncanonically isomorphic to the independently chosen Fourier--Mukai counit triangle.

The isomorphism is the identity on the adjunction-composite and identity vertices. Its third component is the choice made by triangulated-category completion and is not asserted to be natural in Z.

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    @[simp]

    The first component of the counit-triangle comparison is the identity.

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    The second component of the counit-triangle comparison is the identity.

    noncomputable def CategoryTheory.Triangulated.FourierMukai.CounitKernelConeData.transportedTwistObjIso {A : Type uA} {B : Type uB} {X : Type uX} {Y : Type uY} {W₁ : Type u₁} {W₂ : Type u₂} {W : Type uW} [DGCategory A] [DGCategory B] [Category.{vX, uX} X] [Category.{vY, uY} Y] [Category.{v₁, u₁} W₁] [Category.{v₂, u₂} W₂] [Category.{vW, uW} W] {L : DGFunctor A B} {R : DGFunctor B A} {eA : H0 A ≌ X} {eB : H0 B ≌ Y} {C : Correspondence X Y W₁} {C' : Correspondence Y X W₂} {E : Correspondence Y Y W} {P : W₁} {Q : W₂} {e : Enhancement W} {D : ConvolutionData C' C E} {U : UnitKernelData E} [IsPretriangulated B] [Limits.HasZeroObject Y] [HasShift Y ℤ] [Preadditive Y] [∀ (n : ℤ), (shiftFunctor Y n).Additive] [Pretriangulated Y] [eB.functor.CommShift ℤ] [Limits.HasZeroObject W] [HasShift W ℤ] [Preadditive W] [∀ (n : ℤ), (shiftFunctor W n).Additive] [Pretriangulated W] [e.equiv.functor.CommShift ℤ] (adj : DGAdjunction L R) (H : DGAdjunction.H0Presentation eA eB (C.transform P) (C'.transform Q)) (K : adj.CounitConeData) (S : CounitKernelConeData C C' E e P (RightAdjointKernelData.ofH0Presentation H adj) D U) (hE : E.KernelEvaluationExact) [eB.functor.IsTriangulated] [e.equiv.functor.IsTriangulated] (Z : Y) :

    The resulting noncanonical objectwise comparison between the transported actual dg twist and the Fourier--Mukai twist.

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      Supplied natural comparison data #

      @[reducible, inline]
      abbrev CategoryTheory.Triangulated.FourierMukai.CounitKernelConeData.PresentedCounitComparisonData {A : Type uA} {B : Type uB} {X : Type uX} {Y : Type uY} {W₁ : Type u₁} {W₂ : Type u₂} {W : Type uW} [DGCategory A] [DGCategory B] [Category.{vX, uX} X] [Category.{vY, uY} Y] [Category.{v₁, u₁} W₁] [Category.{v₂, u₂} W₂] [Category.{vW, uW} W] {L : DGFunctor A B} {R : DGFunctor B A} {eA : H0 A ≌ X} {eB : H0 B ≌ Y} {C : Correspondence X Y W₁} {C' : Correspondence Y X W₂} {E : Correspondence Y Y W} {P : W₁} {Q : W₂} {e : Enhancement W} {D : ConvolutionData C' C E} {U : UnitKernelData E} [IsPretriangulated B] [Limits.HasZeroObject Y] [HasShift Y ℤ] [Preadditive Y] [∀ (n : ℤ), (shiftFunctor Y n).Additive] [Pretriangulated Y] [eB.functor.CommShift ℤ] [Limits.HasZeroObject W] [HasShift W ℤ] [Preadditive W] [∀ (n : ℤ), (shiftFunctor W n).Additive] [Pretriangulated W] [e.equiv.functor.CommShift ℤ] (adj : DGAdjunction L R) (H : DGAdjunction.H0Presentation eA eB (C.transform P) (C'.transform Q)) (K : adj.CounitConeData) (S : CounitKernelConeData C C' E e P (RightAdjointKernelData.ofH0Presentation H adj) D U) (hE : E.KernelEvaluationExact) :
      Type (max uY vY)

      The genuinely additional data required to supply a separate natural counit-cone comparison of the same triangle families considered objectwise above.

      This is a semantic abbreviation of the generic comparison between two first-map normalizations. It stores a natural isomorphism of the twist functors and compatibility with the two remaining triangle maps.

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        Supply a natural comparison of the transported dg and Fourier--Mukai twists, together with exactly the two triangle-map squares not fixed by the common adjunction counit.

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          The supplied comparison data determine a natural isomorphism between the presented dg and Fourier--Mukai counit-triangle families.

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            @[simp]

            The natural counit-triangle comparison is the identity on the adjunction composite vertex.

            @[simp]

            The natural counit-triangle comparison is the identity on the identity vertex.

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            The third component of the natural counit-triangle comparison is the supplied twist isomorphism.

            The induced natural isomorphism from the transported actual dg twist to the Fourier--Mukai twist.

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              @[simp]

              The projected twist isomorphism is the third-vertex isomorphism supplied by the endpoint-strict comparison data.

              The transported actual dg twist is a kernel functor once a natural comparison with the selected Fourier--Mukai twist has been supplied.

              An explicit equivalence hypothesis on H⁰ of the dg twist transfers to the selected Fourier--Mukai twist through the supplied natural comparison.

              @[reducible]

              The selected twist kernel, packaged as a kernel autoequivalence under the explicit equivalence hypothesis on H⁰ of the dg twist.

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                Compatibility with selected shift structures #

                @[reducible, inline]
                abbrev CategoryTheory.Triangulated.FourierMukai.CounitKernelConeData.PresentedCounitComparisonData.ShiftCompatibility {A : Type uA} {B : Type uB} {X : Type uX} {Y : Type uY} {W₁ : Type u₁} {W₂ : Type u₂} {W : Type uW} [DGCategory A] [DGCategory B] [Category.{vX, uX} X] [Category.{vY, uY} Y] [Category.{v₁, u₁} W₁] [Category.{v₂, u₂} W₂] [Category.{vW, uW} W] {L : DGFunctor A B} {R : DGFunctor B A} {eA : H0 A ≌ X} {eB : H0 B ≌ Y} {C : Correspondence X Y W₁} {C' : Correspondence Y X W₂} {E : Correspondence Y Y W} {P : W₁} {Q : W₂} {e : Enhancement W} {D : ConvolutionData C' C E} {U : UnitKernelData E} [IsPretriangulated B] [Limits.HasZeroObject Y] [HasShift Y ℤ] [Preadditive Y] [∀ (n : ℤ), (shiftFunctor Y n).Additive] [Pretriangulated Y] [eB.functor.CommShift ℤ] [Limits.HasZeroObject W] [HasShift W ℤ] [Preadditive W] [∀ (n : ℤ), (shiftFunctor W n).Additive] [Pretriangulated W] [e.equiv.functor.CommShift ℤ] (adj : DGAdjunction L R) (H : DGAdjunction.H0Presentation eA eB (C.transform P) (C'.transform Q)) (K : adj.CounitConeData) (S : CounitKernelConeData C C' E e P (RightAdjointKernelData.ofH0Presentation H adj) D U) (hE : E.KernelEvaluationExact) (N : PresentedCounitComparisonData adj H K S hE) :
                Type (max uY vY)

                The twist-specific specialization of the shared comparison-shift package. The source is fixed to the canonical shift structure on the transported H⁰ dg twist; the target structure remains independently selected by the realization.

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                  @[implicit_reducible]

                  The selected transported H⁰ shift structure on the dg twist.

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                    @[reducible, inline]

                    The selected shift structure on the Fourier--Mukai twist.

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                      The twist comparison respects its selected source and target shift structures.

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                        The Fourier--Mukai twist is triangulated relative to the selected target shift structure when the supplied comparison respects shifts.

                        theorem CategoryTheory.Triangulated.FourierMukai.CounitKernelConeData.PresentedCounitComparisonData.ShiftCompatibility.twistKernelAutoequivalenceIsTriangulated {A : Type uA} {B : Type uB} {X : Type uX} {Y : Type uY} {W₁ : Type u₁} {W₂ : Type u₂} {W : Type uW} [DGCategory A] [DGCategory B] [Category.{vX, uX} X] [Category.{vY, uY} Y] [Category.{v₁, u₁} W₁] [Category.{v₂, u₂} W₂] [Category.{vW, uW} W] {L : DGFunctor A B} {R : DGFunctor B A} {eA : H0 A ≌ X} {eB : H0 B ≌ Y} {C : Correspondence X Y W₁} {C' : Correspondence Y X W₂} {E : Correspondence Y Y W} {P : W₁} {Q : W₂} {e : Enhancement W} {D : ConvolutionData C' C E} {U : UnitKernelData E} [IsPretriangulated B] [Limits.HasZeroObject Y] [HasShift Y ℤ] [Preadditive Y] [∀ (n : ℤ), (shiftFunctor Y n).Additive] [Pretriangulated Y] [eB.functor.CommShift ℤ] [Limits.HasZeroObject W] [HasShift W ℤ] [Preadditive W] [∀ (n : ℤ), (shiftFunctor W n).Additive] [Pretriangulated W] [e.equiv.functor.CommShift ℤ] (adj : DGAdjunction L R) (H : DGAdjunction.H0Presentation eA eB (C.transform P) (C'.transform Q)) (K : adj.CounitConeData) (S : CounitKernelConeData C C' E e P (RightAdjointKernelData.ofH0Presentation H adj) D U) (hE : E.KernelEvaluationExact) (N : PresentedCounitComparisonData adj H K S hE) (h : ShiftCompatibility adj H K S hE N) [eB.functor.IsTriangulated] (hK : (DGAdjunction.CounitConeData.twist adj K).h0.IsEquivalence) :

                        The kernel autoequivalence of the selected Fourier--Mukai twist is an exact equivalence relative to the selected target shift package.