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Hironaka.Resolution.Analytic.ModelTransport.IdealSheaf

Ideal sheaves along an analytic isomorphism across the models #

The second layer of the model transport (Hironaka/Resolution/Analytic/ModelTransport/). An analytic isomorphism g : N ≃ M between manifolds modelled on E' and E — for the main theorems the identity M.transport ψ → M of Hironaka/Resolution/Analytic/ModelTransport/Manifold.lean and the identities of its open subsets — carries every stalk-level notion of the analytic main theorems from M to N:

The pointwise bodies of HasOnlyNormalCrossingsWith and IsNormalCrossingsDivisor are transported on the ring side (exists_regularSystem_normalCrossings_map, exists_regularSystem_monomial_map); the two directions of each iff are the lemma at the stalk isomorphism and at its inverse. These are chart-independence statements: the predicates of the vocabulary are defined on stalks and see no coordinates.

The germ map of a local analytic isomorphism across the models is bijective: the germ map of a local inverse is a two-sided inverse (germMap_bijective_of_isLocalDiffeomorphAt of Hironaka/Manifold/IdealSheaf/DerivLocality.lean with the two models free; the same proof, the models only in its binders).

Ideals along a ring isomorphism #

The minimal primes of the image of an ideal under a ring isomorphism are the images of its minimal primes (Ideal.comap_minimalPrimes_eq_of_surjective along the inverse).

A ring isomorphism preserves and reflects non-zero-divisors.

theorem Hironaka.Manifold.exists_regularSystem_normalCrossings_map {R : Type u_1} {S : Type u_2} [CommRing R] [CommRing S] (e : R ≃+* S) [IsLocalRing R] [IsLocalRing S] (I J : Ideal R) (h : ∃ (n : ℕ) (z : Fin n → R), (Ideal.span (Set.range z) = IsLocalRing.maximalIdeal R ∧ ↑n = ringKrullDim R) ∧ (∀ P ∈ I.minimalPrimes, ∃ (i : Fin n), P = Ideal.span {z i}) ∧ ∃ (s : Finset (Fin n)), J = Ideal.span (z '' ↑s)) :
∃ (n : ℕ) (z : Fin n → S), (Ideal.span (Set.range z) = IsLocalRing.maximalIdeal S ∧ ↑n = ringKrullDim S) ∧ (∀ P ∈ (Ideal.map e I).minimalPrimes, ∃ (i : Fin n), P = Ideal.span {z i}) ∧ ∃ (s : Finset (Fin n)), Ideal.map e J = Ideal.span (z '' ↑s)

The pointwise body of HasOnlyNormalCrossingsWith (Hironaka's normal crossings at the stalk, [Hir64, Definition 2, p. 141]: a regular system of parameters containing an equation of each minimal prime of I and equations for J) transports along a ring isomorphism of the stalks: the image of a regular system is a regular system (IsLocalRing.map_ringEquiv_maximalIdeal, ringKrullDim_eq_of_ringEquiv), the minimal primes correspond (minimalPrimes_map_ringEquiv).

theorem Hironaka.Manifold.exists_regularSystem_monomial_map {R : Type u_1} {S : Type u_2} [CommRing R] [CommRing S] (e : R ≃+* S) [IsLocalRing R] [IsLocalRing S] (J : Ideal R) (h : ∃ (n : ℕ) (z : Fin n → R) (α : Fin n → ℕ), (Ideal.span (Set.range z) = IsLocalRing.maximalIdeal R ∧ ↑n = ringKrullDim R) ∧ J = Ideal.span {∏ i : Fin n, z i ^ α i}) :
∃ (n : ℕ) (z : Fin n → S) (α : Fin n → ℕ), (Ideal.span (Set.range z) = IsLocalRing.maximalIdeal S ∧ ↑n = ringKrullDim S) ∧ Ideal.map e J = Ideal.span {∏ i : Fin n, z i ^ α i}

The pointwise body of IsNormalCrossingsDivisor (Bierstone–Milman's normal-crossings divisor at the stalk, [BM97, Theorem 1.10]: a monomial in a regular system of parameters) transports along a ring isomorphism of the stalks.

theorem Hironaka.Manifold.ideal_map_symm_map {R : Type u_1} {S : Type u_2} [CommRing R] [CommRing S] (e : R ≃+* S) (I : Ideal R) :

The image under the inverse of the image is the ideal.

The pull-back along an analytic isomorphism across the models #

The stalk isomorphism 𝒪_{M, g b} ≃+* 𝒪_{N, b} of an analytic isomorphism across the models: its germ map, bijective by germMap_bijective_of_isLocalDiffeomorphAt'.

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    theorem Diffeomorph.coe_stalkRingEquiv {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} {E' : Type u_2} [NormedAddCommGroup E] [NormedSpace 𝕜 E] [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {M : AnalyticManifold 𝕜 E} {N : AnalyticManifold 𝕜 E'} (g : Diffeomorph (modelWithCornersSelf 𝕜 E') (modelWithCornersSelf 𝕜 E) N.carrier M.carrier ⊤) (b : N.carrier) :
    ⇑(g.stalkRingEquiv b) = ⇑(Manifold.germMap ⇑g ⋯ b)

    The stalk isomorphism is the germ map on points.

    @[reducible, inline]
    noncomputable abbrev AnalyticManifold.IdealSheaf.pullbackDiffeomorph {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} {E' : Type u_2} [NormedAddCommGroup E] [NormedSpace 𝕜 E] [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {M : AnalyticManifold 𝕜 E} {N : AnalyticManifold 𝕜 E'} (g : Diffeomorph (modelWithCornersSelf 𝕜 E') (modelWithCornersSelf 𝕜 E) N.carrier M.carrier ⊤) (J : M.IdealSheaf) :

    The pull-back of an ideal sheaf along an analytic isomorphism across the models (IdealSheaf.pullback, which takes two models).

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      The stalk of the pull-back is the image of the stalk under the stalk isomorphism.

      The support of the pull-back is the preimage of the support.

      The unit ideal pulls back to the unit ideal.

      The pull-back of a product is the product of the pull-backs.

      The zero ideal sheaf pulls back to the zero ideal sheaf.

      Pulling back along g and then along g⁻¹ is the identity.

      The pull-back along an analytic isomorphism is injective.

      @[reducible, inline]
      abbrev Hironaka.Manifold.IsModelSquare {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} {E' : Type u_2} [NormedAddCommGroup E] [NormedSpace 𝕜 E] [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {M : AnalyticManifold 𝕜 E} {N : AnalyticManifold 𝕜 E'} (g : Diffeomorph (modelWithCornersSelf 𝕜 E') (modelWithCornersSelf 𝕜 E) N.carrier M.carrier ⊤) {M' : AnalyticManifold 𝕜 E} {N' : AnalyticManifold 𝕜 E'} (g' : Diffeomorph (modelWithCornersSelf 𝕜 E') (modelWithCornersSelf 𝕜 E) N'.carrier M'.carrier ⊤) (f : AnalyticMap M' M) (f' : AnalyticMap N' N) :

      The square f ∘ g' = g ∘ f' of two analytic isomorphisms across the models and two analytic maps: the hypothesis of the transport lemmas of Hironaka/Resolution/Analytic/ModelTransport/Square.lean and SquareChart.lean.

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        The pull-back along an analytic map (comap) transports along a square of analytic isomorphisms across the models.

        IsNonsingular (the regularity of the local rings 𝒪_x / J_x) along the isomorphism: the quotients are isomorphic rings (Ideal.quotientEquiv, IsRegularLocalRing.of_ringEquiv).

        The simple locus regularLocus along the isomorphism, the pointwise form of isNonsingular_pullbackDiffeomorph_iff: the quotients 𝒪_b / (g^*J)_b and 𝒪_{g b} / J_{g b} are isomorphic rings.

        IsReduced along the isomorphism (Ideal.IsRadical.comap).

        IsInvertible along the isomorphism: the generating non-zero-divisor is carried by the stalk isomorphism.

        HasOnlyNormalCrossings along the isomorphism.

        The order along the isomorphism (ord_pullback_of_isLocalDiffeomorphAt, which takes two models).

        @[reducible, inline]
        noncomputable abbrev AnalyticManifold.IdealSheaf.transport {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} {E' : Type u_2} [NormedAddCommGroup E] [NormedSpace 𝕜 E] [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {M : AnalyticManifold 𝕜 E} (ψ : E ≃L[𝕜] E') (J : M.IdealSheaf) :

        An ideal sheaf on M read on the re-modelled M: the same sections, pulled back along the identity M.transport ψ → M.

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