Documentation

Hironaka.AnalyticSpace.KSpace.Defs

K-local-ringed spaces #

Hironaka's analytic K-spaces, K = ℝ or ℂ, are K-local-ringed spaces: local-ringed spaces with a structural morphism to Spec K, forming the category ℜ/K of which the analytic K-spaces are the full subcategory An/K [Hir64, Ch. 0, §1, pp. 119–121]. This file defines them and the constructions the rest of the theory rests on: the open subspace X | U, and the K-local-ringed space (M, 𝒪_M) of an analytic manifold together with the K-morphism of an analytic map.

The K-structure #

The K-structure is data: a ring homomorphism K →+* Γ(X, 𝒪_X). By the adjunction between global sections and Spec on locally ringed spaces this is the same as a morphism X → Spec K, and it keeps K : Type while the carrier lives in an arbitrary universe. Morphisms of locally ringed spaces need not respect it: over ℂ the map f(z) ↦ conj (f (conj z)) is a ring automorphism of the convergent power series ring ℂ{z} that is not ℂ-linear, and over ℝ a nonzero ℚ-derivation d of ℝ gives the ring homomorphism r ↦ r + d(r) ε into ℝ[ε]/(ε²), different from the canonical one. The morphisms of K-local-ringed spaces are therefore the K-morphisms: morphisms of locally ringed spaces that commute with the structural homomorphisms on global sections. Every restriction map and every stalk map of a K-morphism is then K-linear (Hom.algebraMap_res, Hom.algebraMap_stalk).

Main definitions #

A K-local-ringed space [Hir64, Ch. 0, §1, p. 119]: a locally ringed space X together with its structural homomorphism algebraMap : K →+* Γ(X, 𝒪_X), the ring-homomorphism form of a morphism X → Spec K.

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    @[reducible, inline]

    The K-morphisms [Hir64, Ch. 0, §1, p. 121]: the morphisms of locally ringed spaces that commute with the structural homomorphisms on global sections.

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      @[instance_reducible]

      The category ℜ/K of K-local-ringed spaces [Hir64, Ch. 0, §1, p. 121].

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      theorem AnalyticSpace.KLocallyRingedSpace.Hom.ext {K : Type} [RCLike K] {X Y : KLocallyRingedSpace K} {f g : X ⟶ Y} (h : ↑f = ↑g) :
      f = g

      A K-morphism is determined by its underlying morphism of locally ringed spaces; the K-condition is a proposition.

      The underlying continuous map of a K-morphism.

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        @[reducible, inline]

        K-isomorphisms: the isomorphisms of the category ℜ/K (Hironaka's "K-isomorphic").

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          A factorization l of the K-morphism a through the K-morphism b is a K-morphism.

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            @[implicit_reducible]

            The open subspace X | U [Hir64, Ch. 0, §1, p. 120]: the restriction of the locally ringed space along the open embedding of U, with the K-structure obtained by restricting the constants.

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              The open immersion X | U ⟶ X as a K-morphism.

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                @[implicit_reducible]

                The locally ringed space (M, 𝒪_M) of an analytic manifold M modelled on E: 𝒪_M is the sheaf of analytic functions on M, whose stalks are local rings, and the constants give the K-structure. For M = Kⁿ this is Hironaka's (Kⁿ, 𝒜_{Kⁿ}), 𝒜_{Kⁿ} the sheaf of germs of analytic K-functions on Kⁿ, with the convergent power series rings K{z₁ - x₁, …, zₙ - xₙ} as stalks [Hir64, Ch. 0, §1].

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                  The K-morphism of an analytic map #

                  A map into an open subset U of a manifold is C^n iff it is C^n as a map into the manifold (Mathlib's ChartedSpace.liftPropWithinAt_subtypeVal_comp_iff, for every n).

                  The continuous map underlying an analytic map, as a morphism of TopCat.

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                    The sheaf map of an analytic map, 𝒪_N ⟶ f_* 𝒪_M: precomposition with f, an analytic function g on U ⊆ N going to g ∘ f on f⁻¹(U).

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                      The evaluation at x of the stalk map applied to a germ at f x is the evaluation of the germ at f x.

                      noncomputable def AnalyticSpace.KLocallyRingedSpace.ofManifoldHom {K : Type} [RCLike K] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace K E] {E' : Type u_2} [NormedAddCommGroup E'] [NormedSpace K E'] {M : Type u} [TopologicalSpace M] [ChartedSpace E M] {N : Type u} [TopologicalSpace N] [ChartedSpace E' N] (f : M → N) (hf : ContMDiff (modelWithCornersSelf K E) (modelWithCornersSelf K E') ⊤ f) :

                      The K-morphism induced by an analytic map f : M → N: base map f, sheaf map precomposition with f; the stalk maps are local since evaluation is preserved and a germ is a unit exactly when its value is nonzero; constants go to constants.

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