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TauCeti.Algebra.Category.ModuleCat.Sheaf.ExteriorPower.Basic

Basic exterior powers of sheaves of modules #

Given a site (C, J) carrying a sheaf of commutative rings R and n : ℕ, the n-th exterior power of a sheaf of R-modules M is obtained by taking sectionwise exterior powers ⋀[R(U)]^n M(U) (PresheafOfModulesOfCommRing.exteriorPower) and sheafifying, exactly as the tensor product TauCeti.SheafOfModules.tensorProduct sheafifies sectionwise tensor products. On a scheme X this gives SheafOfModules.exteriorPower X.sheaf n : X.Modules ⥤ X.Modules, the exterior powers of 𝒪ₓ-modules from which determinants of vector bundles are built.

Main declarations #

The restriction comparison lets local computations of exterior powers, such as those on the charts of a locally free sheaf, be carried out on the restriction to a covering object.

The n-th exterior power of sheaves of R-modules: the sectionwise exterior power of the underlying presheaf of modules, sheafified.

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    The first exterior power of a sheaf of modules is the sheaf itself, naturally.

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      Exterior powers of presheaves of modules commute with the pushforward of presheaves of modules underlying pushforwardModule F R: over X, both sides have sections ⋀[R(F X)]^n M(F X) and the same restriction maps.

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        @[simp]

        The forward map of pushforwardExteriorPowerIso is the sheafification--pushforward comparison followed by the sheafified presheaf-level comparison presheafPushforwardExteriorPowerIso, read through the defining identifications of the two exterior powers.

        pushforwardExteriorPowerIso is natural in the sheaf of modules.