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DerivedAlgGeo.CategoryTheory.Triangulated.FourierMukai.KernelCone

Dg cone diagrams of Fourier--Mukai kernels #

When the kernel category W of a correspondence carries a dg enhancement e : Enhancement W, a DGCategory.ConePresentation e.dgCat is a chosen cone diagram at the enhancement level, and e.coneTriangleFunctor reads it as a triangle of kernels. For each source object, the correspondence's kernel-evaluation functor maps that triangle to a triangle in the target category. More strongly, a globally shift-coherent exact kernel family turns a fixed kernel cone into a functor from source objects to distinguished transform triangles.

The kernel category is enhanced, not identified with an H⁰ on the nose: a geometric kernel category such as Dᵇ(Coh(X × Y)) is only equivalent to the H⁰ of its enhancement, and the comparison equivalence is exactly the datum Enhancement carries. The shift and exactness compatibility of that comparison are instance hypotheses here; supplying them for a concrete enhancement is part of the geometric realization, as is exactness of kernel evaluation itself.

The pointwise transform of the functorial dg cone family of an enhanced kernel category, evaluated at one source object. Its objects are the triangles obtained by applying kernel evaluation to the source, target, and cone kernels; its morphisms retain the maps induced by dg homotopy-coherent cone morphisms.

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    Exactness of a correspondence in the kernel variable, with shift comparisons globally natural in the source object.

    This is the Fourier--Mukai name for the generic Functor.ExactFamily carried by kernelTransform. Its shift structure is Mathlib's ordinary CommShift into the pointwise-shifted functor category, so source naturality and the zero/addition coherences are part of that canonical interface.

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      The pointwise transform-triangle functor obtained from a correspondence whose kernel-variable exactness has been chosen once.

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        A fixed enhanced kernel cone gives a triangle of transform functors, natural in the source object.

        This is the orientation needed by mutations and twists. The earlier coneTriangleFunctor E is recovered by evaluating this functor at E; it is retained because varying the cone presentation is useful independently.

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          Evaluation of the source-natural transform triangle is the previously constructed pointwise image of the kernel cone.

          The pointwise kernel-cone functor with its codomain restricted to distinguished triangles. Consumers that need exact families can use this functor directly instead of carrying a separate objectwise proof.

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            A fixed enhanced kernel cone as a source-indexed functor valued directly in distinguished triangles.

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