4.3. Analytic manifolds and analytic spaces
Lean names in this section are shown relative to AnalyticSpace, Manifold, AnalyticManifold, TopologicalSpace, Topology, Filter, Set.
The theorems of this chapter are the analytic resolution theorems of the library: Hironaka's principalization on a real-analytic manifold, Bierstone–Milman's principalization with the Jacobian condition, Włodarczyk's functorial principalization on a real- or complex-analytic manifold, Włodarczyk's embedded desingularization of a closed subspace of a real- or complex-analytic manifold, the resolution of real- and complex-analytic spaces, and its form for a single reduced complex space.
On a manifold that is not compact no finite succession of blow-ups can be expected to resolve
everything, and Hironaka states his global analytic theorems I′(n), II′(N), I″(n) and II″(N) for
locally finite successions indexed by a countable well-ordered set. The library uses instead the
form of Włodarczyk's locally finite principalization [Wlo09, Theorem 2.0.3]: a proper analytic
map \sigma \colon \tilde M \to M which, over an open neighbourhood U_K of every compact
K \subseteq M, is a finite succession of blow-ups, the successions for different compacts being
compatible (Definition 3.2.2.2). Over a compact manifold, K = M gives one finite
succession.
The objects of the manifold statements are analytic manifolds (Definition 3.1.1.1), locally finitely generated ideal sheaves of analytic functions (Definition 3.1.3.3), finite successions of monoidal transformations with their weak transforms, boundaries and strict transforms (Definition 3.2.1.1, Definition 3.2.1.3), and simple normal crossings boundaries (Definition 3.1.5.1), described in the part on analytic geometry. The section of each theorem states, before the theorem, the properties it asserts; a property asserted by several theorems is stated at the first of them in this chapter.
4.3.1. Main Theorem II″(N), compatible-family form
Main Theorem II″(N) principalizes an ideal sheaf on a real-analytic manifold over every compact subset. Its conditions on boundaries and orders are used again by Bierstone–Milman's principalization and by Włodarczyk's theorems.
Hironaka's conditions on boundaries and orders.
Hironaka's conditions on boundaries and orders, for a finite succession S of an analytic manifold
M with centres C_i; they are the analytic forms of those of the algebraic theorems
(Definition 4.2.1.1, Definition 4.2.3.1):
-
S.HasSncBoundaries B: the boundariesE_istarted atB(Definition 3.2.1.3) have simple normal crossings with the centres, and the last one has simple normal crossings (Definition 3.1.5.1) [Hir64, Main Theorem II′(N) (iii) and the first half of (iv)]; [Wlo09, Theorem 2.0.3 (2)]. Started at the unit ideal⊤, the empty boundary, theE_iare the exceptional divisors; -
S.HasConstantPositiveOrderAlongCenters J: for everyithe order of the weak transformJ_iis a positive constant alongC_i[Hir64, Main Theorem II′(N) (ii)].
Lean code for Definition4.3.1.1●2 definitions
Associated Lean declarations
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structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure FiniteSuccession.HasSncBoundaries {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (S : M.FiniteSuccession) (B : M.IdealSheaf) : Prop
structure FiniteSuccession.HasSncBoundaries {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (S : M.FiniteSuccession) (B : M.IdealSheaf) : Prop
The boundaries
E_iof the successionSstarted atB(S.boundarySeq B:E_0 = BandE_{i+1} = red(σ_{i+1}⁻¹(E_i) ∪ σ_{i+1}⁻¹(D_i))) have simple normal crossings with the centres, and the last one has simple normal crossings ([Hir64, Main Theorem II′(N) (iii) and the first half of (iv), p. 156]; [Wlo09, Theorem 2.0.3 (2)]).Fields
isSncBoundaryWith_center : ∀ (i : Fin S.length), (S.boundarySeq B i.castSucc).IsSncBoundaryWith (S.center i)
The boundary
E_iat the stage of thei-th centre has simple normal crossings with it.isSncBoundary_last : (S.boundarySeq B (Fin.last S.length)).IsSncBoundary
The last boundary
E_rhas simple normal crossings. -
defdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
def FiniteSuccession.HasConstantPositiveOrderAlongCenters {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (S : M.FiniteSuccession) (J : M.IdealSheaf) : Prop := ∀ (i : Fin S.length), ∃ c, 0 < c ∧ ∀ y ∈ IdealSheaf.support (S.center i), IdealSheaf.ord (S.weakTransformSeq J i.castSucc) y = ↑c
def FiniteSuccession.HasConstantPositiveOrderAlongCenters {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (S : M.FiniteSuccession) (J : M.IdealSheaf) : Prop := ∀ (i : Fin S.length), ∃ c, 0 < c ∧ ∀ y ∈ IdealSheaf.support (S.center i), IdealSheaf.ord (S.weakTransformSeq J i.castSucc) y = ↑c
The order of the weak transform
J_iofJ(S.weakTransformSeq J i) is a positive constant along the centreD_i, for everyi([Hir64, Main Theorem II′(N) (ii), p. 156]).
Let X be a real-analytic manifold, E_0 an ideal sheaf with only normal crossings (the reduced
divisor of a simple normal crossings family of smooth hypersurfaces of X), and J_0 an ideal
sheaf with nonzero stalks. Then there are a real-analytic manifold \tilde X and a proper
analytic map \sigma \colon \tilde X \to X which, over an open neighbourhood U_K of every
compact K \subseteq X and compatibly across compacts, is a finite succession of monoidal
transformations U_K = U_0 \leftarrow U_1 \leftarrow \cdots \leftarrow U_r with centres
D_i, such that for every compact K:
-
every centre
D_iis non-singular; -
the order of the weak transform
J_iofJ_0|_{U_K}is a positive constant alongD_i; -
the boundary
E_i(E_0|_{U_K}and thenE_{i+1} = \mathrm{red}(\sigma_{i+1}^{-1}(E_i) \cup \sigma_{i+1}^{-1}(D_i))) has only normal crossings withD_i; -
E_rhas only normal crossings andJ_r = \mathcal{O}_{U_r}.
The conclusion is that of Hironaka's Main Theorem II′(N) (p. 156). This is the real-analytic
counterpart of Main Theorem II(N) (Theorem 4.2.2.1): principalize a nonzero ideal sheaf by
blowing up non-singular centres along which the order of the weak transform is a positive
constant, keeping the boundary in simple normal crossings. The constant of (2) may depend on K
and i. For J_0 = \mathcal{O}_X condition (2) leaves every centre empty, and \sigma is
then an isomorphism.
Condition (2) is HasConstantPositiveOrderAlongCenters and condition (3) with the first half
of (4) HasSncBoundaries (Definition 4.3.1.1).
Lean code for Theorem4.3.1.2●1 theorem
Associated Lean declarations
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theoremdefined in Hironaka/Resolution/Analytic/Wlo09/HironakaAssembly.leancomplete
theorem exists_extensionCompatibleFamily_weakTransformSeq_eq_top {E : Type v} [NormedAddCommGroup E] [NormedSpace ℝ E] (X : AnalyticManifold ℝ E) (E₀ : X.IdealSheaf) (hE₀ : E₀.IsSncBoundary) (J₀ : X.IdealSheaf) (hJ₀ : IdealSheaf.IsNonzeroEverywhere J₀) : ∃ F, IsProperMap ⇑F.map ∧ ∀ (K : Compacts X.carrier), (∀ (i : Fin (F.seq K).length), ((F.seq K).center i).IsNonsingular) ∧ (F.seq K).HasConstantPositiveOrderAlongCenters (J₀.restrict (F.nhd K)) ∧ (F.seq K).HasSncBoundaries (E₀.restrict (F.nhd K)) ∧ (F.seq K).weakTransformSeq (J₀.restrict (F.nhd K)) (Fin.last (F.seq K).length) = ⊤
theorem exists_extensionCompatibleFamily_weakTransformSeq_eq_top {E : Type v} [NormedAddCommGroup E] [NormedSpace ℝ E] (X : AnalyticManifold ℝ E) (E₀ : X.IdealSheaf) (hE₀ : E₀.IsSncBoundary) (J₀ : X.IdealSheaf) (hJ₀ : IdealSheaf.IsNonzeroEverywhere J₀) : ∃ F, IsProperMap ⇑F.map ∧ ∀ (K : Compacts X.carrier), (∀ (i : Fin (F.seq K).length), ((F.seq K).center i).IsNonsingular) ∧ (F.seq K).HasConstantPositiveOrderAlongCenters (J₀.restrict (F.nhd K)) ∧ (F.seq K).HasSncBoundaries (E₀.restrict (F.nhd K)) ∧ (F.seq K).weakTransformSeq (J₀.restrict (F.nhd K)) (Fin.last (F.seq K).length) = ⊤
Hironaka's Main Theorem II″(N) for real-analytic manifolds [Hir64, Main Theorem II″(N), pp. 158–159], whose conclusion is that of Main Theorem II′(N), p. 156, in the compatible-family form of Włodarczyk's locally finite principalization [Wlo09, Theorem 2.0.3 (1) and (4)]. Let
Xbe a real-analytic manifold,E₀an ideal sheaf onXwith only normal crossings (IsSncBoundary), andJ₀an ideal sheaf onXwith nonzero stalks. Then there is a proper analytic mapσ : X̃ → Xwhich over an open neighbourhoodU_Kof every compactK ⊆ Xsplits, compatibly across compacts (ExtensionCompatibleFamily), into a finite succession of monoidal transformationsU_K = U_0 ← U_1 ← ⋯ ← U_rwith centresD_i ⊆ U_isuch that, for every compactK,-
(i) every centre
D_iis non-singular; -
(ii) the order of the weak transform
J_iofJ₀|_{U_K}is a positive constant alongD_i(FiniteSuccession.HasConstantPositiveOrderAlongCenters); -
(iii) with
E_0 = E₀|_{U_K}andE_{i+1} = red(σ_{i+1}⁻¹(E_i) ∪ σ_{i+1}⁻¹(D_i)), everyE_ihas only normal crossings withD_i, and, the first half of (iv),E_rhas only normal crossings (FiniteSuccession.HasSncBoundaries); -
the second half of (iv):
J_r = 𝒪_{U_r}, the unit ideal sheaf⊤.
The constant of (ii) may depend on
Kandi. Clause (i) holds for every finite succession (FiniteSuccession.center_isNonsingular); it is kept as Hironaka's (i). ForJ₀ = 𝒪_Xthe weak transforms are the unit ideal, of order0everywhere, so (ii) leaves every centre empty, andσis then an isomorphism.Source statement: [Hir64, Main Theorem II″(N), pp. 158–159]
Source statement: [Wlo09, Theorem 2.0.3 (1) and (4)]
-
The hypothesis hE₀ provides coordinates E \cong \mathbb{R}^n and a simple normal crossings
hypersurface family whose reduced ideal sheaf is E_0. Transporting X, J_0 and the family
along the coordinates gives a triple on the standard model, to which the order-reduction
algorithm is applied: the real-analytic form of the blow-up sequence functors of
[Kol07, Theorem 103] and, for marked ideals, [Kol07, Theorem 107], assembled functorially over
the exhaustion of the manifold by compacts. This yields a compatible family with proper blow-down
satisfying the conditions on the model, and each condition is carried back along the coordinates.
4.3.2. Real-analytic principalization with the Jacobian condition
Let M be a real-analytic manifold modelled on a finite-dimensional space and I an ideal sheaf
with nonzero stalks. Then there is a proper analytic map \sigma \colon \tilde M \to M which,
over a neighbourhood U_K of every compact K and compatibly across compacts, is a finite
succession of blow-ups U_K = U_0 \leftarrow \cdots \leftarrow U_r with non-singular centres,
such that
-
for every compact
K, the exceptional divisorsE_i(the boundaries started at the empty boundary) have simple normal crossings with the centres, the last oneE_rhas simple normal crossings, and the weak transform ofI|_{U_K}onU_ris the unit ideal; -
the pull-back
\sigma^* Iis a normal-crossings divisor; -
the product of the Jacobian ideal of
\sigmawith\sigma^* Iis a normal-crossings divisor; -
\sigmais an analytic isomorphism over the complement of the support ofI.
The Jacobian condition is what the change of variables in an integral needs: in local coordinates on
\tilde M both I \circ \sigma and the Jacobian determinant of \sigma are monomials times
units. The conditions on the successions are stated over each compact; the normal-crossings,
Jacobian and isomorphism conditions, being local on \tilde M, are stated on \sigma itself. For
I = \mathcal{O}_M the support of I is empty, so \sigma is an isomorphism.
The condition on the exceptional divisors is HasSncBoundaries ⊤
(Definition 4.3.1.1). The additional vocabulary is the Jacobian ideal,
analytic isomorphisms over a set and normal-crossings divisors (Definition 3.1.6.1,
Definition 3.1.5.1).
Lean code for Theorem4.3.2.1●1 theorem
Associated Lean declarations
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theoremdefined in Hironaka/Resolution/Analytic/BM97/JacobianAssembly.leancomplete
theorem exists_extensionCompatibleFamily_isNormalCrossingsDivisor_jacobianIdeal_mul_pullback {E : Type v} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] (M : AnalyticManifold ℝ E) (I : M.IdealSheaf) (hI : IdealSheaf.IsNonzeroEverywhere I) : ∃ F, IsProperMap ⇑F.map ∧ ∀ (K : Compacts M.carrier), (∀ (i : Fin (F.seq K).length), ((F.seq K).center i).IsNonsingular) ∧ (F.seq K).HasSncBoundaries ⊤ ∧ (F.seq K).weakTransformSeq (I.restrict (F.nhd K)) (Fin.last (F.seq K).length) = ⊤ ∧ IdealSheaf.IsNormalCrossingsDivisor (IdealSheaf.pullback ⇑F.map ⋯ I) ∧ (F.map.jacobianIdeal * IdealSheaf.pullback ⇑F.map ⋯ I).IsNormalCrossingsDivisor ∧ F.map.IsIsoOver (IdealSheaf.support I)ᶜ
theorem exists_extensionCompatibleFamily_isNormalCrossingsDivisor_jacobianIdeal_mul_pullback {E : Type v} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] (M : AnalyticManifold ℝ E) (I : M.IdealSheaf) (hI : IdealSheaf.IsNonzeroEverywhere I) : ∃ F, IsProperMap ⇑F.map ∧ ∀ (K : Compacts M.carrier), (∀ (i : Fin (F.seq K).length), ((F.seq K).center i).IsNonsingular) ∧ (F.seq K).HasSncBoundaries ⊤ ∧ (F.seq K).weakTransformSeq (I.restrict (F.nhd K)) (Fin.last (F.seq K).length) = ⊤ ∧ IdealSheaf.IsNormalCrossingsDivisor (IdealSheaf.pullback ⇑F.map ⋯ I) ∧ (F.map.jacobianIdeal * IdealSheaf.pullback ⇑F.map ⋯ I).IsNormalCrossingsDivisor ∧ F.map.IsIsoOver (IdealSheaf.support I)ᶜ
Real-analytic principalization with the Jacobian clause [BM97, Theorem 1.10 and the sentence following it], in the compatible-family form of [Wlo09, Theorem 2.0.3 (1), (2) and (4)]. Let
Mbe a real-analytic manifold modelled on a finite-dimensional real vector space andIan ideal sheaf onMwith nonzero stalks. Then there is a proper analytic mapσ : M̃ → Mwhich over an open neighbourhoodU_Kof every compactK ⊆ Msplits, compatibly across compacts (ExtensionCompatibleFamily), into a finite succession of monoidal transformationsU_K = U_0 ← ⋯ ← U_rwith centresD_i, such that-
for every compact
K: every centreD_iis smooth; the exceptional divisorsE_i, the boundaries started at the empty boundaryE_0 = ⊤, have simple normal crossings with the centres, and the last oneE_rhas simple normal crossings (FiniteSuccession.HasSncBoundaries); and the weak transform ofI|_{U_K}onU_ris the unit ideal sheaf; -
the pull-back
σ*(I)is a normal-crossings divisor (IdealSheaf.IsNormalCrossingsDivisor); -
the product of the Jacobian ideal of
σ(AnalyticMap.jacobianIdeal: the ideal sheaf generated locally, in analytic coordinates, by the Jacobian determinant ofσ) withσ*(I)is a normal-crossings divisor; -
σis an analytic isomorphism over the complement of the support ofI(AnalyticMap.IsIsoOver), the support being Kollár's cosupportcosupp I[Kol07, Theorem 21 (2)].
The clauses on the successions are stated over each compact; the normal-crossings, Jacobian and isomorphism clauses, being local on
M̃, are stated onσitself. ForI = 𝒪_Mthe support ofIis empty, soσis an isomorphism by the last clause.Source statement: [BM97, Theorem 1.10]
Source statement: [Wlo09, Theorem 2.0.3] (compatible-family form)
-
As for Theorem 4.3.1.2: the model space is identified with \mathbb{R}^n, I is
transported to the model, where it forms a triple with the empty boundary family, and the
order-reduction algorithm yields a compatible family whose blow-down is proper, whose successions
satisfy the conditions of Main Theorem II″(N) for the empty boundary, and whose last weak transform
is the unit ideal. The normal-crossings, Jacobian and isomorphism conditions are proved for that
family and carried back along the identification.
4.3.3. Functorial principalization on analytic manifolds
Włodarczyk's functorial principalization assigns a compatible family of finite successions (Definition 3.2.2.2) to every ideal sheaf on every manifold, modelled on any finite-dimensional space, by one rule. It asserts of each value that it is a locally finite principalization, and of the rule that it commutes with local analytic isomorphisms, over the compact sets and globally (every local analytic isomorphism lifts to the spaces of the values), and with closed embeddings of analytic manifolds, over the compact sets.
Locally finite principalization.
I.IsLocallyFinitelyPrincipalizedBy F, for an ideal sheaf I on M and a compatible family F
with map \mathrm{prin}_I, says that F is a locally finite principalization of I in
Włodarczyk's sense. Write F.seq K for the succession over the neighbourhood U_K of a compact
K, with composite \sigma_K and exceptional divisors E_i. Then \mathrm{prin}_I is proper;
every U_K has compact closure; the centres are smooth; (F.seq K).HasSncBoundaries ⊤
(Definition 4.3.1.1); the total transform \sigma_K^*(I|_{U_K}) is near
every point the ideal of an effective combination of the components of E_r
(IsMulBoundaryMonomial with the unit ideal as its first factor,
Definition 3.1.5.2); the total transform \mathrm{prin}_I^*(I) is a normal-crossings
divisor; and \mathrm{prin}_I is an isomorphism off the support of I [Wlo09, Theorem 2.0.3 (1)–(3); Lemma 4.0.3]. It is the analogue on manifolds of Triple.IsPrincipalizedBy on
schemes (Definition 4.2.4.2), with properness and the compact closures of the U_K
added and each condition stated over every compact.
Lean code for Definition4.3.3.1●1 definition
Associated Lean declarations
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structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure IdealSheaf.IsLocallyFinitelyPrincipalizedBy {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (I : M.IdealSheaf) (F : M.ExtensionCompatibleFamily) : Prop
structure IdealSheaf.IsLocallyFinitelyPrincipalizedBy {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (I : M.IdealSheaf) (F : M.ExtensionCompatibleFamily) : Prop
The compatible family
Fis a locally finite principalization of the ideal sheafIonM[Wlo09, Theorem 2.0.3 (1)–(3)]: withprin_I = F.map : M̃ → M, and over the neighbourhoodU_Kof a compactK ⊆ Mthe successionF.seq K : U_K = U_0 ← U_1 ← ⋯ ← U_rwith compositeσ_K : U_r → U_Kand exceptional divisorsE_i(the boundaries(F.seq K).boundarySeq ⊤ istarted at the empty boundary⊤):prin_Iis proper; everyU_Khas compact closure; the centresC_iare smooth; everyE_ihas simple normal crossings withC_iandE_rhas simple normal crossings; the total transformσ_K^*(I|_{U_K})is, near every point, the ideal of an effective combination of the components ofE_rthrough it; the total transformprin_I^*(I)onM̃is a normal-crossings divisor; andprin_Iis an isomorphism over the complement of the support ofI. The compatibility of the successions over two compacts is a field ofExtensionCompatibleFamily. The analogue on manifolds ofTriple.IsPrincipalizedByon schemes, whose fields are Kollár's clauses (1)–(3) for a single blow-up sequence.Fields
isProperMap : IsProperMap ⇑F.map
prin_I : M̃ → Mis proper (the preamble of Theorem 2.0.3).isCompact_closure_nhd : ∀ (K : Compacts M.carrier), IsCompact (closure ↑(F.nhd K))
Every neighbourhood
U_Khas compact closure. Theng(U_K)lies in a compact for every analytic mapgout ofM, so that the commutation with local analytic isomorphisms (IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms) applies to every compact ofM.isNonsingular_center : ∀ (K : Compacts M.carrier) (i : Fin (F.seq K).length), ((F.seq K).center i).IsNonsingular
(1) The centres
C_iare smooth (automatic for every finite succession,FiniteSuccession.center_isNonsingular).hasSncBoundaries : ∀ (K : Compacts M.carrier), (F.seq K).HasSncBoundaries ⊤
(2) Every exceptional divisor
E_ihas simple normal crossings with the centreC_i, andE_rhas simple normal crossings.isMulBoundaryMonomial_pullback : ∀ (K : Compacts M.carrier), IdealSheaf.IsMulBoundaryMonomial (IdealSheaf.pullback ⇑(F.seq K).composite ⋯ (I.restrict (F.nhd K))) ⊤ ((F.seq K).boundarySeq ⊤ (Fin.last (F.seq K).length))
(3) The total transform
σ_K^*(I|_{U_K})is the ideal of a divisorẼ_Uwhich near every point is an effective combination of the components ofE_r(IsMulBoundaryMonomialwith the unit ideal⊤as its first factor).isNormalCrossingsDivisor_pullback : IdealSheaf.IsNormalCrossingsDivisor (IdealSheaf.pullback ⇑F.map ⋯ I)
(3) on
M̃: the total transformprin_I^*(I)is a normal-crossings divisor.isIsoOver_compl_support : F.map.IsIsoOver (IdealSheaf.support I)ᶜ
prin_Iis an isomorphism over the complement of the support ofI([Wlo09, Lemma 4.0.3]; [Kol07, Theorem 35 (3)]).
The inputs: pairs of a manifold and an ideal sheaf.
-
IdealSheafPair[complete] -
IdealSheafPair.pullback[complete]
A pair (M, I) is an analytic manifold M over \mathbb{K}, modelled on a
finite-dimensional space E, with an ideal sheaf I on M with nonzero stalks: the input of
Włodarczyk's principalization, Kollár's triple (X, I, \emptyset) with an empty boundary
(Definition 4.2.4.1). The model space is part of the input, so that one assignment covers the
manifolds of every dimension. T.pullback g hg is the pair (N, g^* I) over a local analytic
isomorphism g \colon N \to M of manifolds modelled on one space, the source of the morphism of
pairs over g [Wlo09, Theorem 3.5.1].
Lean code for Definition4.3.3.2●2 definitions
Associated Lean declarations
-
IdealSheafPair[complete]
-
IdealSheafPair.pullback[complete]
-
IdealSheafPair[complete] -
IdealSheafPair.pullback[complete]
-
structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure IdealSheafPair (𝕜 : Type) [RCLike 𝕜] : Type (max (u + 1) (v + 1))
structure IdealSheafPair (𝕜 : Type) [RCLike 𝕜] : Type (max (u + 1) (v + 1))
A pair
(M, I), the input of Włodarczyk's functorial principalization [Wlo09, Theorem 2.0.3]: an analytic manifoldMover𝕜, modelled on a finite-dimensional spaceE, with an ideal sheafIonMwith nonzero stalks (so on every connected component). Kollár's triple(X, I, ∅)[Kol07, Notation 64] with an empty boundary, on an analytic manifold; the model space is part of the input, so that one assignment covers the manifolds of every dimension.Fields
E : Type v
The model space.
normedAddCommGroup : NormedAddCommGroup self.E
normedSpace : NormedSpace 𝕜 self.E
finiteDimensional : FiniteDimensional 𝕜 self.E
M : AnalyticManifold 𝕜 self.E
The manifold.
I : self.M.IdealSheaf
The ideal sheaf.
isNonzeroEverywhere : IdealSheaf.IsNonzeroEverywhere self.I
Ihas nonzero stalks. -
abbrevdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
abbrev IdealSheafPair.pullback {𝕜 : Type} [RCLike 𝕜] (T : IdealSheafPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g) : IdealSheafPair 𝕜 := { E := T.E, normedAddCommGroup := T.normedAddCommGroup, normedSpace := T.normedSpace, finiteDimensional := ⋯, M := N, I := IdealSheaf.pullback ⇑g ⋯ T.I, isNonzeroEverywhere := ⋯ }
abbrev IdealSheafPair.pullback {𝕜 : Type} [RCLike 𝕜] (T : IdealSheafPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g) : IdealSheafPair 𝕜 := { E := T.E, normedAddCommGroup := T.normedAddCommGroup, normedSpace := T.normedSpace, finiteDimensional := ⋯, M := N, I := IdealSheaf.pullback ⇑g ⋯ T.I, isNonzeroEverywhere := ⋯ }
The pull-back
(N, g^*I)of the pair(M, I)along a local analytic isomorphismg : N → Mof manifolds modelled onE: the source of the morphism of pairs overg[Wlo09, Theorem 3.5.1]. The pulled-back ideal sheaf has nonzero stalks (IdealSheaf.isNonzeroEverywhere_comap).
Compatible family assignments.
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HasUnderlyingManifold[complete] -
CompatibleFamilyAssignment[complete] -
IdealSheafPair.hasUnderlyingManifold[complete]
A type C of inputs has underlying manifolds when every input has an underlying analytic
manifold over \mathbb{K} on a finite-dimensional model space (HasUnderlyingManifold, the
counterpart of HasUnderlyingScheme, Definition 2.4.4.1); the pairs
are such a type. A compatible family assignment on C (CompatibleFamilyAssignment) is a
compatible family of finite successions of blow-ups (Definition 3.2.2.2) of the
underlying manifold of every input: Włodarczyk's \mathrm{prin} and \mathrm{res} as rules on
all pairs, the counterpart on manifolds of a blow-up sequence functor [Kol07, Definition 31].
Its properties are the clauses of the functorial theorems.
Lean code for Definition4.3.3.3●3 definitions
Associated Lean declarations
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HasUnderlyingManifold[complete]
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CompatibleFamilyAssignment[complete]
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IdealSheafPair.hasUnderlyingManifold[complete]
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HasUnderlyingManifold[complete] -
CompatibleFamilyAssignment[complete] -
IdealSheafPair.hasUnderlyingManifold[complete]
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classdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
A type
Cof inputs each with an underlying analytic manifold over𝕜, modelled on a finite-dimensional space (the analogue ofHasUnderlyingSchemefor the algebraic inputs).Methods
model : C → Type v
The model space of the underlying manifold of an input.
normedAddCommGroup : (T : C) → NormedAddCommGroup (HasUnderlyingManifold.model T)
normedSpace : (T : C) → NormedSpace 𝕜 (HasUnderlyingManifold.model T)
finiteDimensional : ∀ (T : C), FiniteDimensional 𝕜 (HasUnderlyingManifold.model T)
manifold : (T : C) → AnalyticManifold 𝕜 (HasUnderlyingManifold.model T)
The underlying manifold of an input.
-
abbrevdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
abbrev CompatibleFamilyAssignment {𝕜 : Type} [RCLike 𝕜] (C : Type w) [HasUnderlyingManifold C 𝕜] : Type (max (max (u + 1) v) w) := (T : C) → (HasUnderlyingManifold.manifold T).ExtensionCompatibleFamily
abbrev CompatibleFamilyAssignment {𝕜 : Type} [RCLike 𝕜] (C : Type w) [HasUnderlyingManifold C 𝕜] : Type (max (max (u + 1) v) w) := (T : C) → (HasUnderlyingManifold.manifold T).ExtensionCompatibleFamily
A compatible family assignment on the inputs
C: a compatible family of finite successions of blow-ups (ExtensionCompatibleFamily) of the underlying manifold of every input — Włodarczyk'sprinandresas rules on all pairs, the counterpart on manifolds of a blow-up sequence functor (BlowUpSequenceFunctor, [Kol07, Definition 31]). Its properties are the clauses of the functorial theorems. -
defdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
def IdealSheafPair.hasUnderlyingManifold {𝕜 : Type} [RCLike 𝕜] : HasUnderlyingManifold (IdealSheafPair 𝕜) 𝕜
def IdealSheafPair.hasUnderlyingManifold {𝕜 : Type} [RCLike 𝕜] : HasUnderlyingManifold (IdealSheafPair 𝕜) 𝕜
The push-forward of an ideal sheaf along a closed embedding.
I.IsPushforwardAlong J τ, for ideal sheaves I on M and J on N and an analytic map
\tau \colon N \to M between analytic manifolds modelled on E' and on E: \tau is a
closed embedding of analytic manifolds, that is an analytic embedding (Mathlib's
IsSmoothEmbedding at \omega: an analytic immersion, of the form u \mapsto (u, 0) in
suitable charts near every point, which is a homeomorphism onto its image) with closed image; the
ideal of its image is contained in I (at every point, the vanishing ideal of \tau(N),
Definition 3.1.3.4, lies in the stalk of I); and J = \tau^* I. So N carries the
analytic structure induced on the closed subset \tau(N) (every analytic map with values in
\tau(N) factors analytically through \tau; for a finite-dimensional model of M,
\tau(N) is a closed submanifold, Definition 3.1.4.1), and the closed subspace of I
lies in \tau(N) and is the image of the closed subspace of J: Kollár's "closed embedding of
smooth schemes" and his hypothesis \mathcal{O}_X / I_X = j_*(\mathcal{O}_Y / I_Y) on the ideal
sheaves in his commutation with closed embeddings, for an empty boundary; the embedding of
Włodarczyk's "embeddings of ambient varieties".
Lean code for Definition4.3.3.4●1 definition
Associated Lean declarations
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IdealSheaf.IsPushforwardAlong[complete]
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IdealSheaf.IsPushforwardAlong[complete]
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structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure IdealSheaf.IsPushforwardAlong {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {E' : Type u_2} [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {M : AnalyticManifold 𝕜 E} {N : AnalyticManifold 𝕜 E'} (I : M.IdealSheaf) (J : N.IdealSheaf) (τ : C^⊤⟮𝓘(𝕜, E'), N.carrier; 𝓘(𝕜, E), M.carrier⟯) : Prop
structure IdealSheaf.IsPushforwardAlong {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {E' : Type u_2} [NormedAddCommGroup E'] [NormedSpace 𝕜 E'] {M : AnalyticManifold 𝕜 E} {N : AnalyticManifold 𝕜 E'} (I : M.IdealSheaf) (J : N.IdealSheaf) (τ : C^⊤⟮𝓘(𝕜, E'), N.carrier; 𝓘(𝕜, E), M.carrier⟯) : Prop
The ideal sheaf
IonMis the push-forward of the ideal sheafJonNalong the closed embedding of analytic manifoldsτ : N → M:τis an analytic embedding (Mathlib'sIsSmoothEmbeddingatω: an analytic immersion, of the formu ↦ (u, 0)in suitable charts near every point, which is a homeomorphism onto its image) with closed image,Icontains the ideal of the closed submanifoldτ(N)(the vanishing idealvanishingStalk, stalk by stalk), andJ = τ^*I. So the closed subspace ofIlies inτ(N)and is the image of the closed subspace ofJ. The imageτ(N)is a closed submanifold ofM(IsClosedAnalyticEmbedding.exists_isClosedSubmanifold, for a finite-dimensional model) andNcarries the analytic structure induced on it: every analytic map intoMwith values inτ(N)factors analytically throughτ(IsClosedAnalyticEmbedding.exists_comp_eq).Fields
isSmoothEmbedding : IsSmoothEmbedding 𝓘(𝕜, E') 𝓘(𝕜, E) ⊤ ⇑τ
τis an analytic embedding: an analytic immersion which is a homeomorphism onto its image.isClosed_range : IsClosed (range ⇑τ)
The image of
τis closed inM.vanishingStalk_le : ∀ (x : M.carrier), vanishingStalk (range ⇑τ) x ≤ IdealSheaf.stalkIdeal I x
The ideal of the image of
τlies inI: at every point the germs vanishing onτ(N)lie in the stalk ofI.pullback_eq : J = IdealSheaf.pullback ⇑τ ⋯ I
J = τ^*I.
Commuting with local analytic isomorphisms.
IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms P, for a compatible family assignment
P on the pairs: the last sentence of [Wlo09, Theorem 2.0.3] for local analytic isomorphisms,
in two forms. Over every pair of compact sets: for a local analytic isomorphism
g \colon N \to M of manifolds modelled on one space, the pair (N, g^* I) and compacts
K' \subseteq N, K \subseteq M with g(U_{K'}) \subseteq U_K, the succession of
P(N, g^* I) over U_{K'} is the pull-back along g of the succession of P(M, I) over
U_K, up to blow-ups with empty centre (Definition 3.2.4.1), the form of
[Wlo09, Theorem 3.5.1 (2)]. Globally: writing \mathrm{prin}_I \colon \tilde M \to M and
\mathrm{prin}_J \colon \tilde N \to N for the maps of P(M, I) and P(N, J), J = g^* I,
there is an analytic map \tilde g \colon \tilde N \to \tilde M with
\mathrm{prin}_I \circ \tilde g = g \circ \mathrm{prin}_J which is a local analytic
isomorphism, maps the fibre of \mathrm{prin}_J over every point y bijectively onto the fibre
of \mathrm{prin}_I over g(y), and is the only continuous map \tilde N \to \tilde M over
g: the "natural lifting" of [Wlo09, Theorem 2.0.1 (3)], whose fibre bijection is the
identification of \tilde N with the fibre product N \times_M \tilde M stated pointwise, and
whose uniqueness makes the lift of a composite the composite of the lifts. The two forms are
bundled as the two conditions of Kollár's 34.1 are in CommutesWithSmoothMorphisms
(Definition 4.2.4.3).
Lean code for Definition4.3.3.5●1 definition
Associated Lean declarations
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structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms {𝕜 : Type} [RCLike 𝕜] (P : CompatibleFamilyAssignment (IdealSheafPair 𝕜)) : Prop
structure IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms {𝕜 : Type} [RCLike 𝕜] (P : CompatibleFamilyAssignment (IdealSheafPair 𝕜)) : Prop
A compatible family assignment
Pon the pairs(M, I)commutes with local analytic isomorphisms, in two forms. Over every pair of compact sets: for a local analytic isomorphismg : N → Mof manifolds modelled on one space, the familyP(N, g^*I)is the pull-back ofP(M, I)alongg(ExtensionCompatibleFamily.IsPullbackAlong): for compactsK' ⊆ N,K ⊆ Mwithg(U_{K'}) ⊆ U_K, the succession ofP(N, g^*I)overU_{K'}is the pull-back alonggof the succession ofP(M, I)overU_K, up to blow-ups with empty centre. Globally: writingprin_I : M̃ → Mandprin_J : Ñ → Nfor the maps ofP(M, I)andP(N, J),J = g^*I, there is an analytic mapg̃ : Ñ → M̃overg(prin_I ∘ g̃ = g ∘ prin_J) which is a local analytic isomorphism, maps the fibre ofprin_Jover everyy ∈ Nbijectively onto the fibre ofprin_Ioverg y, and is the only continuous mapÑ → M̃overg; the fibre bijection with the local isomorphism is the identification ofÑwith the fibre productN ×_M M̃, stated without forming it.Fields
isPullbackAlong : ∀ (T : IdealSheafPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g), (P (T.pullback g hg)).IsPullbackAlong (P T) g
The family
P(N, g^*I)is the pull-back ofP(M, I)alongg, over every pair of compacts.exists_lift : ∀ (T : IdealSheafPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g), ∃ g', (∀ (q : (P (T.pullback g hg)).space.carrier), (P T).map (g' q) = g ((P (T.pullback g hg)).map q)) ∧ IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g' ∧ ∀ (y : N.carrier), BijOn (⇑g') (⇑(P (T.pullback g hg)).map ⁻¹' {y}) (⇑(P T).map ⁻¹' {g y}) ∧ ∀ (φ : (P (T.pullback g hg)).space.carrier → (P T).space.carrier), Continuous φ → (∀ (q : (P (T.pullback g hg)).space.carrier), (P T).map (φ q) = g ((P (T.pullback g hg)).map q)) → φ = ⇑g'
There is an analytic map
g̃ : Ñ → M̃overg, a local analytic isomorphism bijective between the fibres overyand overg y, and the only continuous map overg.
Commuting with closed embeddings.
IdealSheafPair.CommutesWithClosedEmbeddings P, for a compatible family assignment P on the
pairs: for pairs (M, I) and (N, J) and a closed embedding of analytic manifolds
\tau \colon N \to M along which I is the push-forward of J
(Definition 4.3.3.4), and compacts K' \subseteq N, K \subseteq M with
\tau(U_{K'}) \subseteq U_K, the succession of P(M, I) over U_K is the push-forward along
\tau of the succession of P(N, J) over U_{K'}, up to blow-ups whose centres lie outside
the part over \tau(U_{K'}) (Definition 3.2.5.1). This is the rest of the
last sentence of [Wlo09, Theorem 2.0.3], "commutes with … embeddings of ambient varieties", read
as Kollár's commutation with closed embeddings [Kol07, Theorem 35 (5)] in the form of
[Kol07, 34.3], B(X, I_X, E) = j_* B(Y, I_Y, E|_Y) for an empty E, over every pair of
compact sets; the counterpart on manifolds of CommutesWithClosedEmbeddingsOfEmptyBoundary
(Definition 4.2.4.5).
Lean code for Definition4.3.3.6●1 definition
Associated Lean declarations
-
defdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
def IdealSheafPair.CommutesWithClosedEmbeddings {𝕜 : Type} [RCLike 𝕜] (P : CompatibleFamilyAssignment (IdealSheafPair 𝕜)) : Prop := ∀ (T T' : IdealSheafPair 𝕜) (τ : C^⊤⟮𝓘(𝕜, T'.E), T'.M.carrier; 𝓘(𝕜, T.E), T.M.carrier⟯), T.I.IsPushforwardAlong T'.I τ → (P T).IsPushforwardAlong (P T') τ
def IdealSheafPair.CommutesWithClosedEmbeddings {𝕜 : Type} [RCLike 𝕜] (P : CompatibleFamilyAssignment (IdealSheafPair 𝕜)) : Prop := ∀ (T T' : IdealSheafPair 𝕜) (τ : C^⊤⟮𝓘(𝕜, T'.E), T'.M.carrier; 𝓘(𝕜, T.E), T.M.carrier⟯), T.I.IsPushforwardAlong T'.I τ → (P T).IsPushforwardAlong (P T') τ
A compatible family assignment
Pon the pairs(M, I)commutes with closed embeddings: for pairs(M, I)and(N, J)and a closed embedding of analytic manifoldsτ : N → Malong whichIis the push-forward ofJ(IdealSheaf.IsPushforwardAlong:τ(N)a closed submanifold,I ⊇ 𝓘_{τ(N)},J = τ^*I), the familyP(M, I)is the push-forward ofP(N, J)alongτ(ExtensionCompatibleFamily.IsPushforwardAlong): for compactsK' ⊆ N,K ⊆ Mwithτ(U_{K'}) ⊆ U_K, the succession ofP(M, I)overU_Kis the push-forward alongτof the succession ofP(N, J)overU_{K'}, up to blow-ups whose centres lie outside the part overτ(U_{K'}).
Let \mathbb{K} be \mathbb{R} or \mathbb{C}. There is a compatible family assignment P
on the pairs (M, I) of an analytic manifold M over \mathbb{K}, modelled on a
finite-dimensional space, and an ideal sheaf I on M with nonzero stalks
(Definition 4.3.3.2, Definition 4.3.3.3) — to each pair a
map \mathrm{prin}_I \colon \tilde M \to M which over an open neighbourhood U_K of every
compact K \subseteq M is, compatibly across compacts, a finite succession of blow-ups
U_K = U_0 \leftarrow U_1 \leftarrow \cdots \leftarrow U_r with composite \sigma_K —
such that:
-
every value
P(M, I)is a locally finite principalization ofI(Definition 4.3.3.1): with exceptional divisorsE_i,\mathrm{prin}_Iis proper, everyU_Khas compact closure, and (1) the centres are smooth; (2) everyE_ihas simple normal crossings with the centre at its stage, andE_rhas simple normal crossings; (3) the total transform\sigma_K^*(I|_{U_K})is near every point the ideal of an effective combination of the components ofE_r, and the total transform\mathrm{prin}_I^*(I)is a normal-crossings divisor; moreover\mathrm{prin}_Iis an isomorphism off the support ofI; -
Pcommutes with local analytic isomorphisms (Definition 4.3.3.5): for a local analytic isomorphismg \colon N \to Mof manifolds modelled on one space and the pair(N, g^* I), over compactsK' \subseteq N,K \subseteq Mwithg(U_{K'}) \subseteq U_Kthe succession ofP(N, g^* I)overU_{K'}is the pull-back alonggof the succession ofP(M, I)overU_K, up to blow-ups with empty centre; and there is a unique continuous map\tilde g \colon \tilde N \to \tilde Movergbetween the spaces ofP(N, g^* I)andP(M, I), a local analytic isomorphism mapping every fibre of\mathrm{prin}_{g^*I}bijectively onto the fibre of\mathrm{prin}_Iover the image point, so that\tilde N = N \times_M \tilde M; -
Pcommutes with closed embeddings (Definition 4.3.3.6): for pairs(M, I)and(N, J)and a closed embedding of analytic manifolds\tau \colon N \to Malong whichIis the push-forward ofJ(Definition 4.3.3.4), and compactsK' \subseteq N,K \subseteq Mwith\tau(U_{K'}) \subseteq U_K, the succession ofP(M, I)overU_Kis the push-forward along\tauof the succession ofP(N, J)overU_{K'}, up to blow-ups whose centres lie outside the part over\tau(U_{K'}).
Włodarczyk's (4), that the factorization over a larger compact restricts to the factorization over
a smaller one, is the compatibility of the family. This is the analytic counterpart of Kollár's
functorial principalization (Theorem 4.2.4.6) for an empty boundary: the
principalization is chosen for all pairs at once, by one rule, compatibly with local analytic
isomorphisms and with closed embeddings. The three properties are
IdealSheaf.IsLocallyFinitelyPrincipalizedBy,
IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms and
IdealSheafPair.CommutesWithClosedEmbeddings, the second through the pull-back of a
succession up to empty blow-ups (Definition 3.2.4.1) and the third through the
push-forward along a closed embedding (Definition 3.2.5.1).
Lean code for Theorem4.3.3.7●1 theorem
Associated Lean declarations
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exists_functorial_principalization[complete]
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exists_functorial_principalization[complete]
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theoremdefined in Hironaka/Resolution/Analytic/Wlo09/FunctorialPrincipalization.leancomplete
theorem exists_functorial_principalization (𝕜 : Type) [RCLike 𝕜] : ∃ P, (∀ (T : IdealSheafPair 𝕜), T.I.IsLocallyFinitelyPrincipalizedBy (P T)) ∧ IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms P ∧ IdealSheafPair.CommutesWithClosedEmbeddings P
theorem exists_functorial_principalization (𝕜 : Type) [RCLike 𝕜] : ∃ P, (∀ (T : IdealSheafPair 𝕜), T.I.IsLocallyFinitelyPrincipalizedBy (P T)) ∧ IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms P ∧ IdealSheafPair.CommutesWithClosedEmbeddings P
Włodarczyk's functorial locally finite principalization [Wlo09, Theorem 2.0.3], over
𝕜 = ℝor𝕜 = ℂ, the analytic counterpart of Kollár's functorial principalization [Kol07, Theorem 35] for an empty boundary. There is a compatible family assignmentPon the pairs(M, I)of an analytic manifoldMover𝕜, modelled on a finite-dimensional space, and an ideal sheafIonMwith nonzero stalks (CompatibleFamilyAssignment (IdealSheafPair 𝕜)) — to each pair an analytic mapprin_I : M̃ → Mwhich over an open neighbourhoodU_Kof every compactK ⊆ Msplits, compatibly across compacts, into a finite succession of blow-upsU_K = U_0 ← U_1 ← ⋯ ← U_rwith smooth centresC_i ⊆ U_iand compositeσ_K : U_r → U_K— such that-
every value
P(M, I)is a locally finite principalization ofI(IdealSheaf.IsLocallyFinitelyPrincipalizedBy): with exceptional divisorsE_i(the boundaries started at the empty boundary⊤),prin_Iis proper and everyU_Khas compact closure; (1) every centreC_iis smooth; (2) everyE_ihas simple normal crossings withC_i, andE_rhas simple normal crossings (FiniteSuccession.HasSncBoundaries); (3) the total transformσ_K^*(I|_{U_K})is, near every point, the ideal of an effective combination of the components ofE_rthrough it (IdealSheaf.IsMulBoundaryMonomial, with the unit ideal⊤as its first factor), and the total transformprin_I^*(I)onM̃is a normal-crossings divisor (IdealSheaf.IsNormalCrossingsDivisor); andprin_Iis an isomorphism over the complement of the support ofI(AnalyticMap.IsIsoOver); -
Pcommutes with local analytic isomorphisms (IdealSheafPair.CommutesWithLocalAnalyticIsomorphisms): for a local analytic isomorphismg : N → Mof manifolds modelled on one space and the pair(N, g^*I)(IdealSheafPair.pullback), over every pair of compactsK' ⊆ N,K ⊆ Mwithg(U_{K'}) ⊆ U_Kthe succession ofP(N, g^*I)overU_{K'}is the pull-back alonggof the succession ofP(M, I)overU_K, up to blow-ups with empty centre (FiniteSuccession.IsPullbackUpToEmptyAlong; [Wlo09, Theorem 3.5.1 (2)]); and there is a unique continuous mapg̃ : Ñ → M̃overgbetween the spaces ofP(N, g^*I)andP(M, I), which is analytic, a local analytic isomorphism, and maps every fibre ofprin_{g^*I}bijectively onto the fibre ofprin_Iover the image point, so thatÑis the fibre productN ×_M M̃; -
Pcommutes with closed embeddings (IdealSheafPair.CommutesWithClosedEmbeddings): for pairs(M, I)and(N, J)and a closed embedding of analytic manifoldsτ : N → M(an analytic embedding with closed image) along whichIis the push-forward ofJ— the ideal of the closed submanifoldτ(N)lies inI, andJ = τ^*I(IdealSheaf.IsPushforwardAlong) — and compactsK' ⊆ N,K ⊆ Mwithτ(U_{K'}) ⊆ U_K, the succession ofP(M, I)overU_Kis the push-forward alongτof the succession ofP(N, J)overU_{K'}, up to blow-ups whose centres lie outside the part overτ(U_{K'})(FiniteSuccession.IsPushforwardUpToEmptyAlong; [Kol07, 34.3]).
Włodarczyk's (4), that the factorization over a larger compact restricts to the factorization over a smaller one, is the compatibility of the family: the succession over
K ⊆ K', restricted toU_K, is an extension of the succession overK, the same blow-ups with isomorphisms interspersed (ExtensionCompatibleFamily.isExtensionOf_restrict; [Wlo09, Definition 3.2.6]). Centres of codimension one are admitted, as in [Wlo09, Remark (1) after Theorem 2.0.3]: the blow-up of such a centre is an isomorphism, and the centre becomes a component of the exceptional divisor.Source statement: [Wlo09, Theorem 2.0.3, p. 35]
Source statement: [Kol07, Theorem 35] (analytic manifolds, empty boundary; item 44)
-
The model space is identified with \mathbb{K}^n. On a manifold modelled on \mathbb{K}^n the
value at I is Kollár's order reduction of the marked ideal (M, I, \emptyset, 1)
[Kol07, 72], over \mathbb{R} or \mathbb{C} alike: the marked family of the concrete
order-reduction tower at the mark 1 ([Kol07, Theorem 107], the three-step construction of
[Kol07, 111]), over the relatively compact opens, glued along the exhaustion of the manifold.
Over every relatively compact open its value is a smooth blow-up sequence of order at least 1
for (I, \emptyset) whose marked transform has order less than 1 at the end; so its
exceptional divisors are simple normal crossings families having simple normal crossings with the
centres, which gives (1) and (2), the total transform of I is Kollár's monomial in the final
exceptional divisor [Kol07, 72], which gives (3), and the centres lie over the support of I,
which gives the isomorphism off the support. The marked family commutes with local analytic
isomorphisms [Kol07, Theorem 107 (2)]: the value of g^* I over a relatively compact open of
N is the pull-back of the value of I over its image with the empty blow-ups erased, and by the
compatibility of the family the pull-back up to empty blow-ups of the value over any larger
relatively compact open. On a manifold modelled on E the value is the value on the re-modelled
manifold carried back along the identification, with every condition and the pull-back relation;
the assignment on the pairs reads this construction at the model space, the manifold and the
ideal sheaf of each pair.
The lift \tilde g is glued from the pull-back relation: over the neighbourhood U_{K'} of a
compact of N, the compact closure of g(U_{K'}) lies in some U_K, the relation supplies a
local analytic isomorphism between the last stages over g, bijective on the fibres, and through
the identifications of the last stages with the preimages of U_{K'} and U_K it is a map from
a piece of \tilde N to \tilde M over g; two such maps agree on an overlap, because a map
over g is determined on the dense set over which the composite blow-down of U_K is injective
and \tilde M is Hausdorff, so the pieces glue, and the same argument gives the uniqueness.
The commutation with closed embeddings is Kollár's Claim 71.2 [Kol07, 72]: the marked family at
the mark 1 in dimension n commutes with closed embeddings of empty divisor through the marked
family in dimension n - s. For a hypersurface this is [Kol07, Theorem 107 (3)] at the mark
1, which the three-step construction satisfies because an ideal containing the ideal of a
hypersurface has order at most 1, so that its marked order reduction at the mark 1 is a single
round of the order reduction of [Kol07, Theorem 103], whose commutation with closed embeddings
is [Kol07, Theorem 103 (3)]; the general codimension follows along a flag of hypersurfaces
[Kol07, 108]. On the standard models a closed embedding \tau \colon N \to M identifies N
with the bundled closed submanifold \tau(N), by the universal property of the embedding, which
fixes the dimension of N; the value over U_K is the push-forward of the value over the trace
of U_K on \tau(N), the value over U_{K'} is the pull-back up to empty blow-ups of that
value through the identification, and the embeddings of the relation are the inclusions of the
stages of the push-forward after the lifts of the pull-back, which are bijective on the fibres over
U_{K'}. The relation is carried back from the re-modelled manifolds along the identifications of
the two models.
4.3.4. Embedded desingularization of analytic spaces
Włodarczyk's embedded desingularization of a closed subspace of a manifold is stated, like his principalization, over every compact subset, and as an assignment on all pairs of a manifold and a closed subspace. It asserts that the succession over every compact desingularizes the subspace, and that the assignment commutes with local analytic isomorphisms.
Embedded desingularization of a subspace.
For a finite succession S of an analytic manifold M with centres C_i, and the closed
subspace Y with ideal sheaf I, I.IsDesingularizedBy S says, with composite \sigma,
exceptional divisors E_i and strict transforms Y_i, \tilde Y = Y_r: the centres are smooth;
S.HasSncBoundaries ⊤ (Definition 4.3.1.1); no point of a centre lies
over a point of \operatorname{Reg}(Y); the support of E_r is the preimage of
\operatorname{Sing}(Y) = Y \setminus \operatorname{Reg}(Y); \tilde Y is smooth and
IsSncBoundaryTransversalTo holds for E_r and \tilde Y; and
\sigma^*(I_Y) = I_{\tilde Y} \cdot I_{\tilde E} (IsMulBoundaryMonomial,
Definition 3.1.5.2) [Wlo09, Theorem 2.0.2 (1)–(3), (6)]. It is the analogue on manifolds
of EmbeddedPair.IsDesingularizedBy on schemes (Definition 4.2.10.2).
Lean code for Definition4.3.4.1●1 definition
Associated Lean declarations
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IdealSheaf.IsDesingularizedBy[complete]
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IdealSheaf.IsDesingularizedBy[complete]
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structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure IdealSheaf.IsDesingularizedBy {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (I : M.IdealSheaf) (S : M.FiniteSuccession) : Prop
structure IdealSheaf.IsDesingularizedBy {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (I : M.IdealSheaf) (S : M.FiniteSuccession) : Prop
The closed subspace
YofMwith ideal sheafIis desingularized by the finite successionS : M = U_0 ← U_1 ← ⋯ ← U_rwith compositeσ : U_r → M[Wlo09, Theorem 2.0.2 (1)–(3), (6)]. With exceptional divisorsE_i(the boundariesS.boundarySeq ⊤ istarted at the empty boundary⊤) and strict transformsY_iofY(S.strictTransformSubspaceSeq I i),Ỹ = Y_r: the centresC_iare smooth; everyE_ihas simple normal crossings withC_iandE_rhas simple normal crossings; no point of a centre lies over a point ofReg(Y)(regularLocus); the support ofE_ris the preimage ofSing(Y) = Y ∖ Reg(Y);Ỹis smooth and has simple normal crossings withE_r; andσ^*(I_Y) = I_Ỹ · I_ẼwithẼa combination of the components ofE_r. The analogue on manifolds ofEmbeddedPair.IsDesingularizedByon schemes.Fields
isNonsingular_center : ∀ (i : Fin S.length), (S.center i).IsNonsingular
The centres
C_iare smooth (Włodarczyk's "smooth closed centers"; automatic for every finite succession,FiniteSuccession.center_isNonsingular).hasSncBoundaries : S.HasSncBoundaries ⊤
(1) Every exceptional divisor
E_ihas simple normal crossings with the centreC_i, andE_rhas simple normal crossings.stageMap_notMem_regularLocus : ∀ (i : Fin S.length), ∀ x ∈ IdealSheaf.support (S.center i), (S.stageMap i.castSucc) x ∉ I.regularLocus
(2) The centres are disjoint from
Reg(Y): no point of a centreC_ilies over a point whereY(notY_i) is smooth.support_boundarySeq_last : IdealSheaf.support (S.boundarySeq ⊤ (Fin.last S.length)) = ⇑S.composite ⁻¹' (IdealSheaf.support I \ I.regularLocus)
The support of the exceptional divisor
E_ris the exceptional locus, read as the preimageσ⁻¹(Sing Y)of the singular locusSing Y = Y ∖ Reg(Y)(the preamble of Theorem 2.0.2).isNonsingular_strictTransform : (S.strictTransformSubspaceSeq I (Fin.last S.length)).IsNonsingular
(3) The strict transform
Ỹ = Y_ris smooth.isSncBoundaryTransversalTo_strictTransform : (S.boundarySeq ⊤ (Fin.last S.length)).IsSncBoundaryTransversalTo (S.strictTransformSubspaceSeq I (Fin.last S.length))
(3)
Ỹhas simple normal crossings withE_r, transversally.isMulBoundaryMonomial_pullback : IdealSheaf.IsMulBoundaryMonomial (IdealSheaf.pullback ⇑S.composite ⋯ I) (S.strictTransformSubspaceSeq I (Fin.last S.length)) (S.boundarySeq ⊤ (Fin.last S.length))
(6)
σ^*(I_Y) = I_Ỹ · I_Ẽ,Ẽa combination of the components ofE_rnear every point.
Locally finite embedded desingularization.
I.IsLocallyFinitelyDesingularizedBy F, for the ideal sheaf I of a closed subspace Y of
M and a compatible family F with map \mathrm{res}_{Y,M}, says that F is a locally
finite embedded desingularization of Y in Włodarczyk's sense: \mathrm{res}_{Y,M} is proper,
it is an isomorphism over the complement of the singular locus
\operatorname{Sing}(Y) = Y \setminus \operatorname{Reg}(Y), and for every compact K the
succession F.seq K over the neighbourhood U_K desingularizes Y \cap U_K
(I.IsDesingularizedBy, Definition 4.3.4.1), has no empty centre and has
every centre of codimension at least two, or of codimension one inside the exceptional divisor of
its stage, and \tilde M carries an exceptional divisor E and a strict transform \tilde Y
gluing the last exceptional divisors and strict transforms of the successions: over every compact
K, read on the last stage U_r of F.seq K through its identification F.toSpace K with
\mathrm{res}_{Y,M}^{-1}(U_K), E is E_r and \tilde Y the strict transform Y_r of
Y \cap U_K (Definition 3.2.1.3). Then E is the reduced ideal sheaf of a
simple normal crossings family of hypersurfaces, with which \tilde Y has simple normal
crossings, transversally (Definition 3.1.5.2), and
\mathrm{res}_{Y,M}^*(I_Y) = I_{\tilde Y} \cdot I_{\tilde E} with \tilde E near every point
an effective combination of the components of E. His clause (5) is the compatibility of the
family (Definition 3.2.2.2).
Lean code for Definition4.3.4.2●1 definition
Associated Lean declarations
-
structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure IdealSheaf.IsLocallyFinitelyDesingularizedBy {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (I : M.IdealSheaf) (F : M.ExtensionCompatibleFamily) : Prop
structure IdealSheaf.IsLocallyFinitelyDesingularizedBy {𝕜 : Type} [RCLike 𝕜] {E : Type u_1} [NormedAddCommGroup E] [NormedSpace 𝕜 E] {M : AnalyticManifold 𝕜 E} (I : M.IdealSheaf) (F : M.ExtensionCompatibleFamily) : Prop
The compatible family
Fis a locally finite embedded desingularization of the closed subspaceYofMwith ideal sheafI[Wlo09, Theorem 2.0.2]: withres_{Y,M} = F.map : M̃ → M, and over the neighbourhoodU_Kof a compactK ⊆ Mthe successionF.seq K,res_{Y,M}is proper, it is an isomorphism over the complement of the singular locusSing(Y) = Y ∖ Reg(Y), everyF.seq KdesingularizesY ∩ U_K(IsDesingularizedBy, clauses (1)–(3) and (6)), has no empty centre and has every centre of codimension at least two or of codimension one inside the exceptional divisor of its stage, and there are onM̃an exceptional divisorEand a strict transformỸgluing the last exceptional divisors and the last strict transforms of the successions: over every compactK, read on the last stageU_rofF.seq Kthrough its identificationtoSpace Kwithres_{Y,M}⁻¹(U_K),EisE_randỸis the strict transformY_rofY ∩ U_K. ThenEis the reduced ideal sheaf of a simple normal crossings family of hypersurfaces ofM̃with whichỸhas simple normal crossings, transversally, andres_{Y,M}^*(I_Y) = I_Ỹ · I_ẼwithẼnear every point an effective combination of the components ofE. His clause (5), the compatibility of the successions over two compacts, is a field ofExtensionCompatibleFamily.Fields
isProperMap : IsProperMap ⇑F.map
res_{Y,M} : M̃ → Mis proper (the preamble of Theorem 2.0.2).isIsoOver_compl_sing : F.map.IsIsoOver (IdealSheaf.support I \ I.regularLocus)ᶜ
res_{Y,M}is an isomorphism over the complement ofSing(Y) = Y ∖ Reg(Y), more than Włodarczyk's "bimeromorphic": overReg(Y)by his clause (2), overM ∖ Yby [Wlo09, Lemma 4.0.3].isDesingularizedBy_seq : ∀ (K : Compacts M.carrier), (I.restrict (F.nhd K)).IsDesingularizedBy (F.seq K)
Over the neighbourhood
U_Kof every compact, the succession desingularizesY ∩ U_K: [Wlo09, Theorem 2.0.2 (1)–(3), (6)].center_ne_top : ∀ (K : Compacts M.carrier) (i : Fin (F.seq K).length), (F.seq K).center i ≠ ⊤
No centre of any succession is empty: the ideal sheaf of no centre is the unit ideal (the empty blow-up convention [Kol07, 32]; Włodarczyk's centres are nonempty, [Wlo09, Remark (2) after Theorem 2.0.3]).
two_le_codim_or_boundarySeq_le_center : ∀ (K : Compacts M.carrier) (i : Fin (F.seq K).length), 2 ≤ (F.seq K).codim i ∨ (F.seq K).codim i = 1 ∧ ∀ (x : ↑↧((F.seq K).stage i.castSucc).carrier), IdealSheaf.stalkIdeal ((F.seq K).boundarySeq ⊤ i.castSucc) x ≤ IdealSheaf.stalkIdeal ((F.seq K).center i) x
Every centre
C_ihas codimension at least two, or has codimension one and lies in the exceptional divisorE_iof its stage, the reduced ideal sheaf ofE_ilying in its ideal sheaf: then its blow-up is an isomorphism and it becomes a component of the exceptional divisor [Wlo09, Remarks (1) and (2) after Theorem 2.0.3].exists_divisor_strictTransform : ∃ E_1 Y, (∀ (K : Compacts M.carrier), IdealSheaf.pullback ⇑(F.toSpace K) ⋯ E_1 = (F.seq K).boundarySeq ⊤ (Fin.last (F.seq K).length) ∧ IdealSheaf.pullback ⇑(F.toSpace K) ⋯ Y = (F.seq K).strictTransformSubspaceSeq (I.restrict (F.nhd K)) (Fin.last (F.seq K).length)) ∧ E_1.IsSncBoundaryTransversalTo Y ∧ IdealSheaf.IsMulBoundaryMonomial (IdealSheaf.pullback ⇑F.map ⋯ I) Y E_1
Włodarczyk's divisor
Eand strict transformỸ(hereY) onM̃: they glue the last exceptional divisors and strict transforms of the successions over the compacts,Eis a simple normal crossings divisor with whichỸis transversal ((1), (3)), andres^*(I_Y) = I_Ỹ · I_Ẽ((6)).
The inputs: embedded pairs.
-
EmbeddedPair[complete] -
EmbeddedPair.pullback[complete] -
EmbeddedPair.hasUnderlyingManifold[complete]
An embedded pair (M, Y) is an analytic manifold M over \mathbb{K}, modelled on a
finite-dimensional space, with a reduced closed analytic subspace Y \subseteq M, given by its
ideal sheaf: the input of Włodarczyk's embedded desingularization, the counterpart on manifolds of
the algebraic embedded pair (Definition 4.2.10.1), with the model space part of the
input as for Definition 4.3.3.2; the embedded pairs have underlying manifolds
(Definition 4.3.3.3). T.pullback g hg is the embedded pair
(N, g^{-1}(Y)) over a local analytic isomorphism g \colon N \to M of manifolds modelled on
one space; its subspace is reduced since the germ maps of g are ring isomorphisms.
Lean code for Definition4.3.4.3●3 definitions
Associated Lean declarations
-
EmbeddedPair[complete]
-
EmbeddedPair.pullback[complete]
-
EmbeddedPair.hasUnderlyingManifold[complete]
-
EmbeddedPair[complete] -
EmbeddedPair.pullback[complete] -
EmbeddedPair.hasUnderlyingManifold[complete]
-
structuredefined in Hironaka/Manifold/Resolution/Defs.leancomplete
structure EmbeddedPair (𝕜 : Type) [RCLike 𝕜] : Type (max (u + 1) (v + 1))
structure EmbeddedPair (𝕜 : Type) [RCLike 𝕜] : Type (max (u + 1) (v + 1))
An embedded pair
(M, Y), the input of Włodarczyk's locally finite embedded desingularization [Wlo09, Theorem 2.0.2]: an analytic manifoldMover𝕜, modelled on a finite-dimensional spaceE, with a reduced closed analytic subspaceY ⊆ M, given by its ideal sheaf (every stalk radical). The analogue on manifolds of the algebraicAlgebraicGeometry.EmbeddedPairof Włodarczyk's embedded desingularization with smooth centres; the model space is part of the input, as forIdealSheafPair.Fields
E : Type v
The model space.
normedAddCommGroup : NormedAddCommGroup self.E
normedSpace : NormedSpace 𝕜 self.E
finiteDimensional : FiniteDimensional 𝕜 self.E
M : AnalyticManifold 𝕜 self.E
The ambient manifold.
Y : self.M.IdealSheaf
The ideal sheaf of the embedded subspace.
isReduced : self.Y.IsReduced
The embedded subspace is reduced: every stalk of its ideal sheaf is radical.
-
abbrevdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
abbrev EmbeddedPair.pullback {𝕜 : Type} [RCLike 𝕜] (T : EmbeddedPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g) : EmbeddedPair 𝕜 := { E := T.E, normedAddCommGroup := T.normedAddCommGroup, normedSpace := T.normedSpace, finiteDimensional := ⋯, M := N, Y := IdealSheaf.pullback ⇑g ⋯ T.Y, isReduced := ⋯ }
abbrev EmbeddedPair.pullback {𝕜 : Type} [RCLike 𝕜] (T : EmbeddedPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g) : EmbeddedPair 𝕜 := { E := T.E, normedAddCommGroup := T.normedAddCommGroup, normedSpace := T.normedSpace, finiteDimensional := ⋯, M := N, Y := IdealSheaf.pullback ⇑g ⋯ T.Y, isReduced := ⋯ }
The pull-back
(N, g^{-1}(Y))of the embedded pair(M, Y)along a local analytic isomorphismg : N → Mof manifolds modelled onE: the source of the morphism of embedded pairs overg[Wlo09, Theorem 3.5.1]. The pulled-back ideal sheaf is reduced (IdealSheaf.isReduced_pullback_of_isLocalDiffeomorph). -
defdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
def EmbeddedPair.hasUnderlyingManifold {𝕜 : Type} [RCLike 𝕜] : HasUnderlyingManifold (EmbeddedPair 𝕜) 𝕜
def EmbeddedPair.hasUnderlyingManifold {𝕜 : Type} [RCLike 𝕜] : HasUnderlyingManifold (EmbeddedPair 𝕜) 𝕜
Commuting with local analytic isomorphisms.
EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms R, for a compatible family assignment R
on the embedded pairs: for a local analytic isomorphism g \colon N \to M of manifolds modelled
on one space, the embedded pair (N, g^{-1}(Y)) and compacts K' \subseteq N,
K \subseteq M with g(U_{K'}) \subseteq U_K, the succession of R(N, g^{-1}(Y)) over
U_{K'} is the pull-back along g of the succession of R(M, Y) over U_K, up to blow-ups
with empty centre (Definition 3.2.4.1): the first half of
[Wlo09, Theorem 2.0.2 (4)], read as [Wlo09, Theorem 3.5.1 (2)], the per-compact form of
Definition 4.3.3.5 (the lift of the local isomorphism is not stated for the
embedded desingularization).
Lean code for Definition4.3.4.4●1 definition
Associated Lean declarations
-
defdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
def EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms {𝕜 : Type} [RCLike 𝕜] (R : CompatibleFamilyAssignment (EmbeddedPair 𝕜)) : Prop := ∀ (T : EmbeddedPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g), (R (T.pullback g hg)).IsPullbackAlong (R T) g
def EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms {𝕜 : Type} [RCLike 𝕜] (R : CompatibleFamilyAssignment (EmbeddedPair 𝕜)) : Prop := ∀ (T : EmbeddedPair 𝕜) {N : AnalyticManifold 𝕜 T.E} (g : AnalyticMap N T.M) (hg : IsLocalDiffeomorph 𝓘(𝕜, T.E) 𝓘(𝕜, T.E) ⊤ ⇑g), (R (T.pullback g hg)).IsPullbackAlong (R T) g
A compatible family assignment
Ron the embedded pairs(M, Y)commutes with local analytic isomorphisms: for a local analytic isomorphismg : N → Mof manifolds modelled on one space and the embedded pair(N, g^{-1}(Y)), the familyR(N, g^{-1}(Y))is the pull-back ofR(M, Y)alongg(ExtensionCompatibleFamily.IsPullbackAlong): for compactsK' ⊆ N,K ⊆ Mwithg(U_{K'}) ⊆ U_K, the succession ofR(N, g^{-1}(Y))overU_{K'}is the pull-back alonggof the succession ofR(M, Y)overU_K, up to blow-ups with empty centre.
Commuting with closed embeddings of ambient manifolds.
EmbeddedPair.CommutesWithClosedEmbeddings R, for a compatible family assignment R on the
embedded pairs: for embedded pairs (M, Y) and (N, Y') and a closed embedding of analytic
manifolds \tau \colon N \to M along which the ideal sheaf of Y is the push-forward of that
of Y' (Definition 4.3.3.4: \tau(N) a closed submanifold containing Y,
and Y' = \tau^{-1}(Y)), such that no connected component of N lies in Y' (the ideal
sheaf of Y' has nonzero stalks, Kollár's 0 \neq I_Y), and compacts K' \subseteq N,
K \subseteq M with \tau(U_{K'}) \subseteq U_K, the succession of R(M, Y) over U_K is
the push-forward along \tau of the succession of R(N, Y') over U_{K'}, up to blow-ups
whose centres lie outside the part over \tau(U_{K'})
(Definition 3.2.5.1): the second half of [Wlo09, Theorem 2.0.2 (4)],
"embeddings of ambient varieties", read as [Kol07, 34.3] as Definition 4.3.3.6
reads the last sentence of Theorem 2.0.3.
Lean code for Definition4.3.4.5●1 definition
Associated Lean declarations
-
defdefined in Hironaka/Manifold/Resolution/Defs.leancomplete
def EmbeddedPair.CommutesWithClosedEmbeddings {𝕜 : Type} [RCLike 𝕜] (R : CompatibleFamilyAssignment (EmbeddedPair 𝕜)) : Prop := ∀ (T T' : EmbeddedPair 𝕜) (τ : C^⊤⟮𝓘(𝕜, T'.E), T'.M.carrier; 𝓘(𝕜, T.E), T.M.carrier⟯), T.Y.IsPushforwardAlong T'.Y τ → IdealSheaf.IsNonzeroEverywhere T'.Y → (R T).IsPushforwardAlong (R T') τ
def EmbeddedPair.CommutesWithClosedEmbeddings {𝕜 : Type} [RCLike 𝕜] (R : CompatibleFamilyAssignment (EmbeddedPair 𝕜)) : Prop := ∀ (T T' : EmbeddedPair 𝕜) (τ : C^⊤⟮𝓘(𝕜, T'.E), T'.M.carrier; 𝓘(𝕜, T.E), T.M.carrier⟯), T.Y.IsPushforwardAlong T'.Y τ → IdealSheaf.IsNonzeroEverywhere T'.Y → (R T).IsPushforwardAlong (R T') τ
A compatible family assignment
Ron the embedded pairs commutes with closed embeddings of ambient manifolds: for embedded pairs(M, Y)and(N, Y')and a closed embedding of analytic manifoldsτ : N → Malong which the ideal sheaf ofYis the push-forward of that ofY'(IdealSheaf.IsPushforwardAlong:τ(N)a closed submanifold containingY, andY' = τ^{-1}(Y)), such that no connected component ofNlies inY'(the ideal sheaf ofY'has nonzero stalks), the familyR(M, Y)is the push-forward ofR(N, Y')alongτ(ExtensionCompatibleFamily.IsPushforwardAlong): for compactsK' ⊆ N,K ⊆ Mwithτ(U_{K'}) ⊆ U_K, the succession ofR(M, Y)overU_Kis the push-forward alongτof the succession ofR(N, Y')overU_{K'}, up to blow-ups whose centres lie outside the part overτ(U_{K'}).
Let \mathbb{K} be \mathbb{R} or \mathbb{C}. There is a compatible family assignment R
on the embedded pairs (M, Y) of an analytic manifold M over \mathbb{K}, modelled on a
finite-dimensional space, and a reduced closed analytic subspace Y \subseteq M with ideal sheaf
I_Y (Definition 4.3.4.3, Definition 4.3.3.3) —
to each pair a map \mathrm{res}_{Y,M} \colon \tilde M \to M which over an open neighbourhood
U_K of every compact K \subseteq M is, compatibly across compacts, a finite succession of
blow-ups U_K = U_0 \leftarrow U_1 \leftarrow \cdots \leftarrow U_r with smooth closed centres
C_i and composite \sigma_K \colon U_r \to U_K — such that:
-
every value
R(M, Y)is a locally finite embedded desingularization ofY(Definition 4.3.4.2):\mathrm{res}_{Y,M}is proper and an isomorphism over the complement of the singular locus\operatorname{Sing}(Y) = Y \setminus \operatorname{Reg}(Y), and for every compactK, with exceptional divisorsE_i(the boundaries started at the empty boundary), strict transformsY_iofY \cap U_Kand\tilde Y = Y_r: every centreC_iis smooth; (1) everyE_ihas simple normal crossings withC_i, andE_rhas simple normal crossings; (2) no point of a centreC_ilies over a point of\operatorname{Reg}(Y); the support ofE_ris the preimage\sigma_K^{-1}(\operatorname{Sing} Y); (3)\tilde Yis smooth and has simple normal crossings withE_r, no component ofE_rcontaining\tilde Ynear a point; (6)\sigma_K^*(I_Y) = I_{\tilde Y} \cdot I_{\tilde E}, with\tilde Enear every point an effective combination of the components ofE_r; and\tilde Mcarries an exceptional divisorEand a strict transform\tilde Y:Eis the reduced ideal sheaf of a simple normal crossings family of hypersurfaces, with which\tilde Yhas simple normal crossings, transversally,\mathrm{res}_{Y,M}^*(I_Y) = I_{\tilde Y} \cdot I_{\tilde E}with\tilde Enear every point an effective combination of the components ofE, and over every compactK, read onU_r \cong \mathrm{res}_{Y,M}^{-1}(U_K),EisE_rand\tilde YisY_r; no centre of any succession is empty, and every centre has codimension at least two, or has codimension one and lies in the exceptional divisor of its stage; -
(4)
Rcommutes with local analytic isomorphisms (Definition 4.3.4.4): for a local analytic isomorphismg \colon N \to Mof manifolds modelled on one space, the embedded pair(N, g^{-1}(Y))and compactsK' \subseteq N,K \subseteq Mwithg(U_{K'}) \subseteq U_K, the succession ofR(N, g^{-1}(Y))overU_{K'}is the pull-back alonggof the succession ofR(M, Y)overU_K, up to blow-ups with empty centre; -
(4)
Rcommutes with closed embeddings of ambient manifolds (Definition 4.3.4.5): for embedded pairs(M, Y)and(N, Y')and a closed embedding of analytic manifolds\tau \colon N \to Malong whichI_Yis the push-forward ofI_{Y'}(\tau(N)a closed submanifold containingY, andY' = \tau^{-1}(Y)), such that no connected component ofNlies inY', and compactsK' \subseteq N,K \subseteq Mwith\tau(U_{K'}) \subseteq U_K, the succession ofR(M, Y)overU_Kis the push-forward along\tauof the succession ofR(N, Y')overU_{K'}, up to blow-ups whose centres lie outside the part over\tau(U_{K'}).
Włodarczyk's (5), that the factorization over a larger compact restricts to the factorization over
a smaller one, is the compatibility of the family: the succession over K \subseteq K',
restricted to U_K, is an extension of the succession over K [Wlo09, Definition 3.2.6].
This is the analytic counterpart of Włodarczyk's algebraic embedded desingularization
(Theorem 4.2.10.4), in the locally finite form of Theorem 4.3.1.2, chosen for all
embedded pairs at once, by one rule, compatibly with local analytic isomorphisms and with closed
embeddings of ambient manifolds.
The three properties are IdealSheaf.IsLocallyFinitelyDesingularizedBy
(Definition 4.3.4.2), whose conditions on the successions
are IdealSheaf.IsDesingularizedBy (Definition 4.3.4.1), built on
the strict transforms of a closed subspace (Definition 3.2.1.3), the simple
locus \operatorname{Reg}(Y) and reducedness (Definition 3.1.3.3), and the
transversal simple normal crossings and monomial factorization predicates
(Definition 3.1.5.2), in which it also states its conditions on the exceptional divisor
and the strict transform on \tilde M;
EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms
(Definition 4.3.4.4), through the pull-back of a succession up to empty
blow-ups (Definition 3.2.4.1); and
EmbeddedPair.CommutesWithClosedEmbeddings (Definition 4.3.4.5),
through the push-forward along a closed embedding (Definition 3.2.5.1).
Lean code for Theorem4.3.4.6●1 theorem
Associated Lean declarations
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exists_embeddedDesingularization[complete]
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exists_embeddedDesingularization[complete]
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theoremdefined in Hironaka/Resolution/Analytic/Wlo09/EmbeddedDesingularization.leancomplete
theorem exists_embeddedDesingularization (𝕜 : Type) [RCLike 𝕜] : ∃ R, (∀ (T : EmbeddedPair 𝕜), T.Y.IsLocallyFinitelyDesingularizedBy (R T)) ∧ EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms R ∧ EmbeddedPair.CommutesWithClosedEmbeddings R
theorem exists_embeddedDesingularization (𝕜 : Type) [RCLike 𝕜] : ∃ R, (∀ (T : EmbeddedPair 𝕜), T.Y.IsLocallyFinitelyDesingularizedBy (R T)) ∧ EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms R ∧ EmbeddedPair.CommutesWithClosedEmbeddings R
Włodarczyk's locally finite embedded desingularization [Wlo09, Theorem 2.0.2], over
𝕜 = ℝor𝕜 = ℂ, with its commutation with local analytic isomorphisms and with closed embeddings of ambient manifolds. There is a compatible family assignmentRon the embedded pairs(M, Y)of an analytic manifoldMover𝕜, modelled on a finite-dimensional space, and a reduced closed analytic subspaceY ⊆ Mwith ideal sheafI_Y(CompatibleFamilyAssignment (EmbeddedPair 𝕜)) — to each pair an analytic mapres_{Y,M} : M̃ → Mwhich over an open neighbourhoodU_Kof every compactK ⊆ Msplits, compatibly across compacts, into a finite succession of blow-upsU_K = U_0 ← U_1 ← ⋯ ← U_rwith smooth closed centresC_i ⊆ U_iand compositeσ_K : U_r → U_K— such that-
every value
R(M, Y)is a locally finite embedded desingularization ofY(IdealSheaf.IsLocallyFinitelyDesingularizedBy):res_{Y,M}is proper and an isomorphism off the singular locusSing(Y) = Y ∖ Reg(Y); over every compact the succession satisfies (1)–(3) and (6) (IdealSheaf.IsDesingularizedBy), has no empty centre, and has every centre of codimension at least two or of codimension one inside the exceptional divisor of its stage; andM̃carries a divisorEand a strict transformỸrestricting toE_randY_rover every compact, with (1), (3) and (6) onM̃; -
(4)
Rcommutes with local analytic isomorphisms (EmbeddedPair.CommutesWithLocalAnalyticIsomorphisms): for a local analytic isomorphismg : N → Mof manifolds modelled on one space and compactsK' ⊆ N,K ⊆ Mwithg(U_{K'}) ⊆ U_K, the succession ofR(N, g^{-1}(Y))(EmbeddedPair.pullback) overU_{K'}is the pull-back alonggof the succession ofR(M, Y)overU_K, up to blow-ups with empty centre (FiniteSuccession.IsPullbackUpToEmptyAlong; [Wlo09, Theorem 3.5.1 (2)]); -
(4)
Rcommutes with closed embeddings of ambient manifolds (EmbeddedPair.CommutesWithClosedEmbeddings): for a closed embedding of analytic manifoldsτ : N → M(an analytic embedding with closed image) along whichI_Yis the push-forward ofI_{Y'}(IdealSheaf.IsPushforwardAlong:τ(N)containsY, andY' = τ^{-1}(Y)), no connected component ofNlying inY', and compactsK' ⊆ N,K ⊆ Mwithτ(U_{K'}) ⊆ U_K, the succession ofR(M, Y)overU_Kis the push-forward alongτof that ofR(N, Y')overU_{K'}, up to blow-ups whose centres lie outside the part overτ(U_{K'})(FiniteSuccession.IsPushforwardUpToEmptyAlong; [Kol07, 34.3]).
Włodarczyk's (5), that the factorization over a larger compact restricts to the factorization over a smaller one, is the compatibility of the family: the succession over
K ⊆ K', restricted toU_K, is an extension of that overK(ExtensionCompatibleFamily.isExtensionOf_restrict; [Wlo09, Definition 3.2.6]).Source statement: [Wlo09, Theorem 2.0.2]
-
The model space is identified with \mathbb{K}^n and I is transported to the model, where,
made the unit ideal on the connected components of M on which it vanishes (a union of
components, by the identity theorem), it forms a triple with the empty boundary family. Włodarczyk's modification of the resolution
algorithm for the marked ideal (M, I, \emptyset, 1) (the proof of [Wlo09, Theorem 7.4.1]: the
algorithm is stopped as soon as the controlled transform is the ideal of a smooth hypersurface of
maximal contact), run on the real- or complex-analytic form of the blow-up sequence functors of
[Kol07, Theorem 103] and [Kol07, Theorem 107], gives an embedded desingularization functor over
the relatively compact opens of the model, which is glued along the exhaustion of the manifold to
a compatible family with a proper blow-down. Its centres lie over Y by the order condition of the
algorithm, hence over \operatorname{Sing}(Y) by (2), so the blow-down is an isomorphism over the
complement of \operatorname{Sing}(Y); and the support of E_r is the preimage of
\operatorname{Sing}(Y), because off E_r the composite blow-down is an isomorphism near the
point, carrying the smooth \tilde Y onto Y. Over the components where I vanishes nothing
is blown up, the strict transform is the component itself and the exceptional divisor is empty,
so every condition holds for I as it does for the modified ideal sheaf. The exceptional
families of the pieces glue to a locally finite simple normal crossings family on the glued
space, each member born on the piece where it first appears and continued along the embeddings of
the pieces, which carry exceptional families to exceptional families; E is its reduced ideal
sheaf, and \tilde Y is the saturation of the total transform \mathrm{res}_{Y,M}^*(I) by E,
which on each piece is the last strict transform [BM97, Proposition 3.13], the strict transform
being, at a point of the last stage, the saturation of the total transform by the exceptional
ideal: near a point of \tilde Y the exceptional ideal is a product of coordinates and the ideal
of \tilde Y a prime generated by coordinates not among them, so the saturation changes
nothing. The conditions on E and \tilde Y are read on the pieces through the inclusions,
which are local analytic isomorphisms. The functor commutes with local analytic isomorphisms
[Kol07, 34.1]: the value of g^* I over a relatively compact
open is the pull-back of the value of I over its image with the empty blow-ups erased, and by
the compatibility of the family the pull-back up to empty blow-ups of the value over any larger
relatively compact open. The commutation with closed embeddings of ambient manifolds is that of
the functor over the relatively compact opens, through the functor of the lower dimension at the
restriction of I to the submanifold, which is reduced when I is and contains the ideal of the
submanifold: on the standard models the embedding identifies N with the bundled submanifold,
the value over U_K is the push-forward of the value over the trace of U_K on \tau(N), and
the value over U_{K'} is the pull-back up to empty blow-ups of that value through the
identification, as for the principalization; the modification of I on its zero components is
invisible along \tau(N), since J has nonzero stalks. Each condition and the two relations
are carried back along the identifications of the models. A centre of codimension at most one
lies over \operatorname{Sing}(Y) and has simple normal crossings with the exceptional divisor
of its stage; off that divisor the composite blow-down is a local isomorphism and would carry
the centre, a smooth hypersurface or an open set, into \operatorname{Sing}(Y), which contains
neither: the singular locus of a reduced subspace contains no smooth hypersurface germ, since the
stalk of the ideal sheaf at a point of such a germ would lie in every power of its equation,
hence vanish by Krull's intersection theorem; so the centre lies in the exceptional divisor and
has codimension one.
4.3.5. Resolution of analytic spaces
The resolution of analytic spaces is a resolution assignment
(Definition 3.3.4.1), a morphism \Pi_X \colon R(X) \to X for every analytic
space X, here on the reduced spaces. It asserts of the values that they are strong resolutions
onto the closure of the simple locus and locally composites of blow-ups of an ambient manifold, and
of the assignment that it lifts isomorphisms between open subspaces of inputs and local analytic
isomorphisms between inputs. The resolution of a single reduced complex space asserts
the first two properties again.
Strong resolutions of analytic spaces.
-
Hom.IsResolution[complete] -
Hom.IsStrongResolution[complete] -
Hom.IsStrongResolutionOntoClosureRegularLocus[complete]
For a morphism \pi \colon R \to X of K-analytic spaces:
-
π.IsResolution:Ris non-singular,\piis proper, and\piis bimeromorphic (Kollár: birational [Kol07, (2)]; [Wlo09, Theorem 2.0.1]), read onto its image: an isomorphism over an open subsetU \subseteq Xwhose preimage is dense inR. Kollár asks for\piprojective; only the properness that projectivity implies is recorded. The density is asked of the preimage and not ofU: over\mathbb{R}the simple locus of a reduced space need not be dense, and then no resolution is an isomorphism over a dense open subset ofX. -
π.IsStrongResolution[Kol07, (3)], conditions (1)–(3) of Kollár's Theorem 45: a resolution that is an isomorphism over the simple locusX.regularLocusand such that\pi^{-1}(\operatorname{Sing} X)is the support of a closed subspaceEwithE.IsSncBoundary(Definition 3.3.3.3). -
π.IsStrongResolutionOntoClosureRegularLocus: a strong resolution whose image is the closure of the simple locus ofX, conditions (1)–(3) of Theorem 45 with the image clause. Over\mathbb{C}the simple locus of a reduced space is dense and the clause is the surjectivity of\pi; over\mathbb{R}it need not be dense, and\pimisses the part ofXaway from the closure of the simple points.
Lean code for Definition4.3.5.1●3 definitions
Associated Lean declarations
-
Hom.IsResolution[complete]
-
Hom.IsStrongResolution[complete]
-
Hom.IsStrongResolutionOntoClosureRegularLocus[complete]
-
Hom.IsResolution[complete] -
Hom.IsStrongResolution[complete] -
Hom.IsStrongResolutionOntoClosureRegularLocus[complete]
-
structuredefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
structure Hom.IsResolution {K : Type} [RCLike K] {X R : AnalyticSpace K} (π : R ⟶ X) : Prop
structure Hom.IsResolution {K : Type} [RCLike K] {X R : AnalyticSpace K} (π : R ⟶ X) : Prop
A morphism
π : R → XofK-analytic spaces is a resolution ofX:Ris non-singular,πis proper, andπis bimeromorphic (Kollár: birational [Kol07, (2)]; [Wlo09, Theorem 2.0.1]), read onto its image: an isomorphism over an open subsetU ⊆ Xwhose preimage is dense inR. Kollár asks forπprojective; only the properness that projectivity implies is recorded. The density is asked of the preimage and not ofU: overℝthe simple locus of a reduced space need not be dense ([Hir64, Introduction]), and then no resolution is an isomorphism over a dense open subset ofX.Fields
isNonsingular : R.IsNonsingular
Ris non-singular.isProperMap : IsProperMap ↑π
πis proper [Kol07, (2)] (Kollár: projective).exists_isIsoOver_dense_preimage : ∃ U, IsOpen U ∧ Hom.IsIsoOver π U ∧ Dense (↑π ⁻¹' U)
πis an isomorphism over an open subset ofXwhose preimage is dense inR. -
structuredefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
structure Hom.IsStrongResolution {K : Type} [RCLike K] {X R : AnalyticSpace K} (π : R ⟶ X) : Prop
structure Hom.IsStrongResolution {K : Type} [RCLike K] {X R : AnalyticSpace K} (π : R ⟶ X) : Prop
A morphism
π : R → XofK-analytic spaces is a strong resolution ofX[Kol07, (3)], clauses (1)–(3) of [Kol07, Theorem 45]: a resolution (non-singular, proper, bimeromorphic onto its image) that is an isomorphism over the simple locusX.regularLocus(Kollár's smooth locusX^{ns}), and such thatπ⁻¹(X.singularLocus)is the support of a simple normal crossing divisor ofR: a closed subspace which is the reduced divisor of a locally finite family of closed smooth hypersurfaces with simple normal crossings (ClosedSubspace.IsSncBoundary; [Kol07, Definition 24]).Extends
Fields
isNonsingular : R.IsNonsingular
Inherited from-
AnalyticSpace.Hom.IsResolution
isProperMap : IsProperMap ↑π
Inherited from-
AnalyticSpace.Hom.IsResolution
exists_isIsoOver_dense_preimage : ∃ U, IsOpen U ∧ Hom.IsIsoOver π U ∧ Dense (↑π ⁻¹' U)
Inherited from-
AnalyticSpace.Hom.IsResolution
isIsoOver_regularLocus : Hom.IsIsoOver π X.regularLocus
πis an isomorphism over the simple locusX^{ns}.exists_isSncBoundary_preimage : ∃ E, E.IsSncBoundary ∧ IdealSheaf.support E = ↑π ⁻¹' X.singularLocus
π⁻¹(Sing X)is the support of a simple normal crossing divisor. -
-
structuredefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
structure Hom.IsStrongResolutionOntoClosureRegularLocus {K : Type} [RCLike K] {X R : AnalyticSpace K} (π : R ⟶ X) : Prop
structure Hom.IsStrongResolutionOntoClosureRegularLocus {K : Type} [RCLike K] {X R : AnalyticSpace K} (π : R ⟶ X) : Prop
A morphism
π : R → XofK-analytic spaces is a strong resolution onto the closure of the simple locus ofX: a strong resolution (Hom.IsStrongResolution: non-singular, proper, bimeromorphic onto its image, an isomorphism over the simple locusX.regularLocus, andπ⁻¹(Sing X)the support of a simple normal crossing divisor — clauses (1)–(3) of [Kol07, Theorem 45]) whose image is the closure of the simple locus. Overℂthe simple locus of a reduced space is dense and the clause says thatπis surjective; overℝit need not be dense ([Hir64, Introduction]: the subspacex² + y² = 0ofℝ²is reduced with support the origin and no simple point), and thenπmisses the part ofXaway from the closure of the simple points.Extends
Fields
isNonsingular : R.IsNonsingular
Inherited from-
AnalyticSpace.Hom.IsStrongResolution -
AnalyticSpace.Hom.IsResolution
isProperMap : IsProperMap ↑π
Inherited from-
AnalyticSpace.Hom.IsStrongResolution -
AnalyticSpace.Hom.IsResolution
exists_isIsoOver_dense_preimage : ∃ U, IsOpen U ∧ Hom.IsIsoOver π U ∧ Dense (↑π ⁻¹' U)
Inherited from-
AnalyticSpace.Hom.IsStrongResolution -
AnalyticSpace.Hom.IsResolution
isIsoOver_regularLocus : Hom.IsIsoOver π X.regularLocus
Inherited from-
AnalyticSpace.Hom.IsStrongResolution
exists_isSncBoundary_preimage : ∃ E, E.IsSncBoundary ∧ IdealSheaf.support E = ↑π ⁻¹' X.singularLocus
Inherited from-
AnalyticSpace.Hom.IsStrongResolution
range_eq : range ↑π = closure X.regularLocus
The image of
πis the closure of the simple locus ofX. -
Local factorization through ambient blow-ups.
-
ChartedSpace.sigma[complete] -
ChartedSpace.sigmaOfNonempty[complete] -
sigmaOpens[complete] -
IdealSheaf.toAnalyticSpace[complete] -
IdealSheaf.toAnalyticSpaceι[complete] -
IdealSheaf.overPiece[complete] -
Hom.AmbientBlowUpFactorization[complete] -
Hom.IsLocallyFiniteAmbientBlowUpComposite[complete]
Condition (4) of the resolution theorem describes \Pi_X locally as a composite of blow-ups of an
ambient manifold restricted to strict transforms. The ambient is a disjoint union
A = \bigsqcup_i G_i of countably many open subsets of K^n
(AnalyticManifold.sigmaOpens, built on the charted space structure of a disjoint union,
ChartedSpace.sigma, ChartedSpace.sigmaOfNonempty). An ideal sheaf J on A cuts
out the closed subspace \operatorname{Sp}(A)/J (IdealSheaf.toAnalyticSpace, with its
morphism toAnalyticSpaceι), and overPiece is its part over G_i.
An ambient blow-up factorization f.AmbientBlowUpFactorization U of f \colon Y \to X over an
open U (Hom.AmbientBlowUpFactorization) consists of finitely many open subspaces U_i
covering U, closed embeddings of the X|_{U_i} into open subsets G_i \subseteq K^n, a
finite succession of blow-ups of the ambient A with smooth centres, the strict transforms of
\bigsqcup X|_{U_i}, the last one a closed submanifold, and isomorphisms over each U_i
identifying f^{-1}(U_i) \to U_i with the restricted composite [Kol07, Warning 23];
[Wlo09, Theorem 2.0.2]. f.IsLocallyFiniteAmbientBlowUpComposite asks for such a factorization
over every relatively compact open U \subseteq X.
Lean code for Definition4.3.5.2●8 definitions
Associated Lean declarations
-
ChartedSpace.sigma[complete]
-
ChartedSpace.sigmaOfNonempty[complete]
-
sigmaOpens[complete]
-
IdealSheaf.toAnalyticSpace[complete]
-
IdealSheaf.toAnalyticSpaceι[complete]
-
IdealSheaf.overPiece[complete]
-
Hom.AmbientBlowUpFactorization[complete]
-
Hom.IsLocallyFiniteAmbientBlowUpComposite[complete]
-
ChartedSpace.sigma[complete] -
ChartedSpace.sigmaOfNonempty[complete] -
sigmaOpens[complete] -
IdealSheaf.toAnalyticSpace[complete] -
IdealSheaf.toAnalyticSpaceι[complete] -
IdealSheaf.overPiece[complete] -
Hom.AmbientBlowUpFactorization[complete] -
Hom.IsLocallyFiniteAmbientBlowUpComposite[complete]
-
defdefined in Hironaka/Manifold/DisjointUnion/Defs.leancomplete
def ChartedSpace.sigma {ι : Type u_1} {H : Type u_2} [TopologicalSpace H] (M : ι → Type u_3) [(i : ι) → TopologicalSpace (M i)] [cm : (i : ι) → ChartedSpace H (M i)] : ChartedSpace H ((i : ι) × M i)
def ChartedSpace.sigma {ι : Type u_1} {H : Type u_2} [TopologicalSpace H] (M : ι → Type u_3) [(i : ι) → TopologicalSpace (M i)] [cm : (i : ι) → ChartedSpace H (M i)] : ChartedSpace H ((i : ι) × M i)
The disjoint union
Σ i, M iof charted spaces modelled onHis a charted space modelled onH(forHempty everyM iis empty, and so is the union). -
defdefined in Hironaka/Manifold/DisjointUnion/Defs.leancomplete
def ChartedSpace.sigmaOfNonempty {ι : Type u_1} {H : Type u_2} [TopologicalSpace H] (M : ι → Type u_3) [(i : ι) → TopologicalSpace (M i)] [cm : (i : ι) → ChartedSpace H (M i)] [Nonempty H] : ChartedSpace H ((i : ι) × M i) := { atlas := ⋃ i, (fun e => e.lift_openEmbedding ⋯) '' ChartedSpace.atlas, chartAt := fun p => (ChartedSpace.chartAt p.snd).lift_openEmbedding ⋯, mem_chart_source := ⋯, chart_mem_atlas := ⋯ }
def ChartedSpace.sigmaOfNonempty {ι : Type u_1} {H : Type u_2} [TopologicalSpace H] (M : ι → Type u_3) [(i : ι) → TopologicalSpace (M i)] [cm : (i : ι) → ChartedSpace H (M i)] [Nonempty H] : ChartedSpace H ((i : ι) × M i) := { atlas := ⋃ i, (fun e => e.lift_openEmbedding ⋯) '' ChartedSpace.atlas, chartAt := fun p => (ChartedSpace.chartAt p.snd).lift_openEmbedding ⋯, mem_chart_source := ⋯, chart_mem_atlas := ⋯ }
The disjoint union of a family of charted spaces modelled on a nonempty
His a charted space modelled onH: the charts are the charts of theM i, lifted along the open embeddingsSigma.mk i. -
defdefined in Hironaka/Manifold/AnalyticManifold/Defs.leancomplete
def sigmaOpens {K : Type} [RCLike K] {n : ℕ} {ι : Type u} [Countable ι] (G : ι → Opens (Fin n → K)) : AnalyticManifold K (Fin n → K) := { carrier := (i : ι) × ↥(G i), top := instTopologicalSpaceSigma, charted := ChartedSpace.sigma fun i => ↥(G i), manifold := ⋯, t2 := ⋯, secondCountable := ⋯ }
def sigmaOpens {K : Type} [RCLike K] {n : ℕ} {ι : Type u} [Countable ι] (G : ι → Opens (Fin n → K)) : AnalyticManifold K (Fin n → K) := { carrier := (i : ι) × ↥(G i), top := instTopologicalSpaceSigma, charted := ChartedSpace.sigma fun i => ↥(G i), manifold := ⋯, t2 := ⋯, secondCountable := ⋯ }
The disjoint union
A := ⊔ᵢ Gᵢof a countable family of open subsetsGᵢ ⊆ Kⁿas an analytic manifold modelled onKⁿ(the ambientX' = ⊔ Uᵢof the proof of [Kol07, Proposition 37]): theΣ-type with the charts of the summands (ChartedSpace.sigma,IsManifold.sigma), Hausdorff as a disjoint union of Hausdorff spaces and second countable for a countable index. -
defdefined in Hironaka/AnalyticSpace/Manifold/Defs.leancomplete
def IdealSheaf.toAnalyticSpace {K : Type} [RCLike K] {n : ℕ} {A : AnalyticManifold K (Fin n → K)} (J : A.IdealSheaf) : AnalyticSpace K := (toSpace (ContinuousLinearEquiv.refl K (Fin n → K)) A).closedSubspace J
def IdealSheaf.toAnalyticSpace {K : Type} [RCLike K] {n : ℕ} {A : AnalyticManifold K (Fin n → K)} (J : A.IdealSheaf) : AnalyticSpace K := (toSpace (ContinuousLinearEquiv.refl K (Fin n → K)) A).closedSubspace J
The closed analytic subspace
Sp(A)/Jof the spaceSp(A)of an analytic manifoldAmodelled onKⁿ, cut out by the ideal sheafJ, as an analyticK-space:closedSubspaceonSp(A)(the coordinates onKⁿthe identity, as inIsSncDivisorSet). -
defdefined in Hironaka/AnalyticSpace/Manifold/Defs.leancomplete
def IdealSheaf.toAnalyticSpaceι {K : Type} [RCLike K] {n : ℕ} {A : AnalyticManifold K (Fin n → K)} (J : A.IdealSheaf) : J.toAnalyticSpace ⟶ toSpace (ContinuousLinearEquiv.refl K (Fin n → K)) A := (toSpace (ContinuousLinearEquiv.refl K (Fin n → K)) A).closedSubspaceι J
def IdealSheaf.toAnalyticSpaceι {K : Type} [RCLike K] {n : ℕ} {A : AnalyticManifold K (Fin n → K)} (J : A.IdealSheaf) : J.toAnalyticSpace ⟶ toSpace (ContinuousLinearEquiv.refl K (Fin n → K)) A := (toSpace (ContinuousLinearEquiv.refl K (Fin n → K)) A).closedSubspaceι J
The canonical morphism
Sp(A)/J ⟶ Sp(A)of the closed subspace. -
defdefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
def IdealSheaf.overPiece {K : Type} [RCLike K] {n : ℕ} {ι : Type u} [Countable ι] {G : ι → Opens (Fin n → K)} (J : (sigmaOpens G).IdealSheaf) (i : ι) : Set ↑↑J.toAnalyticSpace.toPresheafedSpace := {y | (↑J.toAnalyticSpaceι y).fst = i}
def IdealSheaf.overPiece {K : Type} [RCLike K] {n : ℕ} {ι : Type u} [Countable ι] {G : ι → Opens (Fin n → K)} (J : (sigmaOpens G).IdealSheaf) (i : ι) : Set ↑↑J.toAnalyticSpace.toPresheafedSpace := {y | (↑J.toAnalyticSpaceι y).fst = i}
The part of the closed subspace
Sp(A)/JofA = ⊔ᵢ Gᵢlying over the summandGᵢ: the points whose image inAhas indexi. -
structuredefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
structure Hom.AmbientBlowUpFactorization {K : Type} [RCLike K] {X Y : AnalyticSpace K} (f : Y ⟶ X) (U : Set ↑↑X.toPresheafedSpace) : Type (u + 1)
structure Hom.AmbientBlowUpFactorization {K : Type} [RCLike K] {X Y : AnalyticSpace K} (f : Y ⟶ X) (U : Set ↑↑X.toPresheafedSpace) : Type (u + 1)
An ambient blow-up factorization of
f : Y → Xover the openU ⊆ X(after [Kol07, Warning 23] and the local factorization (∗) of [Wlo09, Theorem 2.0.2], with the disjoint-union ambient of the proof of [Kol07, Proposition 37]): finitely many open subspacesUᵢcoveringU; closed embeddingsX|Uᵢ ↪ Gᵢ ⊆ Kⁿ(onenfor alli, by padding), given as the ideal sheafJ₀on the ambientA := ⊔ᵢ Gᵢ(sigmaOpens) of the closed subspaceY₀ = ⊔ᵢ X|Uᵢtogether with isomorphisms ofX|Uᵢwith the part ofSp(A)/J₀overGᵢ; a finite sequenceπ₀, …, π_{r-1}of blow-ups ofAwith smooth centres (aFiniteSuccession); the strict transformsY₀, …, Y_r,Y_{k+1}the strict transform ofY_kunderπ_k, of finite type (the saturation of the pulled-back ideal along the exceptional divisor has local generators), withY_ra closed submanifold ofA_r; and, for eachi, an isomorphism overUᵢoff⁻¹(Uᵢ) → UᵢwithΠ_r|_{Y_r} : Y_r → Y₀ = X|Uᵢ,Π_r = π₀ ∘ ⋯ ∘ π_{r-1}(the morphism of closed subspaces overΠ_r, unique since the canonical morphism of a closed subspace is a monomorphism), over the pieceGᵢ.Fields
n : ℕ
The common dimension
nof the ambient piecesGᵢ ⊆ Kⁿ.ι : Type u
The finite index set of the pieces.
finite : Finite self.ι
piece : self.ι → Set ↑↑X.toPresheafedSpace
The open subspaces
Uᵢ ⊆ X…isOpen_piece : ∀ (i : self.ι), IsOpen (self.piece i)
subset_iUnion_piece : U ⊆ ⋃ i, self.piece i
… covering
U.G : self.ι → Opens (Fin self.n → K)
The open subsets
Gᵢ ⊆ Kⁿ.ideal : (sigmaOpens self.G).IdealSheaf
The ideal sheaf
J₀onA = ⊔ᵢ Gᵢof the closed subspaceY₀ = ⊔ᵢ X|Uᵢ(locally finitely generated).emb : (i : self.ι) → X.restrictSet (self.piece i) ⟶ self.ideal.toAnalyticSpace.restrictSet (self.ideal.overPiece i)
The closed embeddings:
X|Uᵢis isomorphic to the part ofY₀ = Sp(A)/J₀overGᵢ…emb_isIso : ∀ (i : self.ι), CategoryTheory.IsIso (self.emb i)
… as analytic
K-spaces.seq : (sigmaOpens self.G).FiniteSuccession
The finite sequence of blow-ups
π₀, …, π_{r-1}ofAwith smooth centres.transform : (k : Fin (self.seq.length + 1)) → (self.seq.stage k).IdealSheaf
The closed subspaces
Y_k ⊆ A_kof the stages, …transform_zero : self.transform 0 = self.ideal
… starting with
Y₀, …transform_succ : ∀ (k : Fin self.seq.length), self.transform k.succ = strictTransformSubspace ⋯ ⋯ (self.transform k.castSucc)
…
Y_{k+1}the strict transform ofY_kunderπ_k(strictTransformSubspaceat the witnesses of thek-th blow-up), …hasLocalGenerators_saturation : ∀ (k : Fin self.seq.length), IdealSheaf.HasLocalGenerators (saturationStalk ⋯ ⋯ (self.transform k.castSucc))
… of finite type: the saturation
⋃_m (π_k⁻¹(I_{Y_k}) : I_{F}^m)has local generators, soY_{k+1}is the saturation and not the unit-ideal fallback ofstrictTransformSubspace.isNonsingular_last : (self.transform (Fin.last self.seq.length)).IsNonsingular
Y_ris a closed submanifold ofA_r: every point ofY_ris simple.map : (self.transform (Fin.last self.seq.length)).toAnalyticSpace ⟶ self.ideal.toAnalyticSpace
Π_r|_{Y_r} : Y_r → Y₀, the morphism of closed subspaces …map_comp : self.map ≫ self.ideal.toAnalyticSpaceι = (self.transform (Fin.last self.seq.length)).toAnalyticSpaceι ≫ toSpaceHom (ContinuousLinearEquiv.refl K (Fin self.n → K)) self.seq.composite
… lying over
Π_r = π₀ ∘ ⋯ ∘ π_{r-1}(thecompositeof the succession).lift : (i : self.ι) → Y.restrictSet (↑f ⁻¹' self.piece i) ⟶ (self.transform (Fin.last self.seq.length)).toAnalyticSpace.restrictSet (↑self.map ⁻¹' self.ideal.overPiece i)
The isomorphism over
Uᵢoff⁻¹(Uᵢ) → UᵢwithΠ_r|_{Y_r}over the pieceGᵢ:f⁻¹(Uᵢ)is isomorphic to the part ofY_roverGᵢ…lift_isIso : ∀ (i : self.ι), CategoryTheory.IsIso (self.lift i)
map_lift : ∀ (i : self.ι), self.lift i ≫ Hom.restrictSet self.map (self.ideal.overPiece i) = Hom.restrictSet f (self.piece i) ≫ self.emb i
… compatibly with
fandΠ_r|_{Y_r}. -
defdefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
def Hom.IsLocallyFiniteAmbientBlowUpComposite {K : Type} [RCLike K] {X Y : AnalyticSpace K} (f : Y ⟶ X) : Prop := ∀ (U : Set ↑↑X.toPresheafedSpace), IsOpen U → IsCompact (closure U) → Nonempty (Hom.AmbientBlowUpFactorization f U)
def Hom.IsLocallyFiniteAmbientBlowUpComposite {K : Type} [RCLike K] {X Y : AnalyticSpace K} (f : Y ⟶ X) : Prop := ∀ (U : Set ↑↑X.toPresheafedSpace), IsOpen U → IsCompact (closure U) → Nonempty (Hom.AmbientBlowUpFactorization f U)
Clause (4) of [Kol07, Theorem 45], "
Π_Xis projective over any compact subset ofX", in the form of [Kol07, Warning 23] and of the local factorization (∗) of [Wlo09, Theorem 2.0.2]: over every relatively compact openU ⊆ X,frestricted tof⁻¹(U)is the composite of a finite sequence of blow-ups of smooth centres of an ambient manifold, restricted to strict transforms — anf.AmbientBlowUpFactorization U. The clause plays the role of Hironaka's local finiteness of a succession [Hir64, Ch. 0, §7, p. 155]: every point has a relatively compact open neighbourhood over whichfis one finite composite (no compatibility between the factorizations over different opens is asserted).
Lifting local analytic isomorphisms.
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Hom.IsLocalIso[complete] -
ResolutionAssignment.LiftsLocalIsomorphisms[complete]
A morphism \varphi \colon X' \to X of analytic spaces is a local analytic isomorphism
(Hom.IsLocalIso) when every point of X' has an open neighbourhood U' which \varphi
maps isomorphically onto an open subspace X|_V: open immersions, isomorphisms, covering maps and
the morphism \coprod U_i \to X from the disjoint union of an open cover, injective or not. A
morphism \psi \colon A \to B is the only morphism over \varphi \colon X \to Y, along
p \colon A \to X and q \colon B \to Y, when the morphisms \psi' with
q \circ \psi' = \varphi \circ p are exactly \psi. A resolution assignment R on inputs C (Definition 3.3.4.1)
lifts local analytic isomorphisms (R.LiftsLocalIsomorphisms) in two forms: every isomorphism
\varphi \colon X|_U \to Y|_V between open subspaces of two inputs lifts to exactly one morphism
\psi \colon R(X)|_{\Pi_X^{-1} U} \to R(Y)|_{\Pi_Y^{-1} V} over \varphi, an isomorphism; and
every local analytic isomorphism \varphi \colon X' \to X between inputs lifts to exactly one
morphism \psi \colon R(X') \to R(X) with \Pi_X \circ \psi = \varphi \circ \Pi_{X'}, a local
analytic isomorphism. Over every open U' which \varphi maps isomorphically onto an open
subspace, the lift of \varphi restricts to the lift of that isomorphism, since the restriction
lies over it and the lift of the first form is the only morphism over it. Because the lifts are
unique, they
respect identities and composition: R is a functor on the groupoid of isomorphisms between open
subspaces of inputs and on the local analytic isomorphisms between inputs. The first form stands
for condition (5) of Kollár's Theorem 45, "R commutes with smooth K-morphisms", for the étale
morphisms that are injective, and the second is [Wlo09, Theorem 2.0.1 (3)] and the case of étale
morphisms of Kollár's (5); the two are bundled as the two conditions of Kollár's 34.1 are in
CommutesWithSmoothMorphisms (Definition 4.2.4.3). Smooth morphisms that are not
étale are not lifted. For strong resolutions, the second form follows from the first by gluing the
local lifts over the opens on which \varphi is injective, the gluing being compatible on the
overlaps because a morphism out of a non-singular space is determined on a dense open subset.
Lean code for Definition4.3.5.3●2 definitions
Associated Lean declarations
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Hom.IsLocalIso[complete]
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ResolutionAssignment.LiftsLocalIsomorphisms[complete]
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Hom.IsLocalIso[complete] -
ResolutionAssignment.LiftsLocalIsomorphisms[complete]
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defdefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
def Hom.IsLocalIso {K : Type} [RCLike K] {X' X : AnalyticSpace K} (φ : X' ⟶ X) : Prop := ∀ (x' : ↑↑X'.toPresheafedSpace), ∃ U' V, IsOpen U' ∧ IsOpen V ∧ x' ∈ U' ∧ ∃ χ, CategoryTheory.IsIso χ ∧ χ ≫ X.ofRestrict (X.openOf V) = X'.ofRestrict (X'.openOf U') ≫ φ
def Hom.IsLocalIso {K : Type} [RCLike K] {X' X : AnalyticSpace K} (φ : X' ⟶ X) : Prop := ∀ (x' : ↑↑X'.toPresheafedSpace), ∃ U' V, IsOpen U' ∧ IsOpen V ∧ x' ∈ U' ∧ ∃ χ, CategoryTheory.IsIso χ ∧ χ ≫ X.ofRestrict (X.openOf V) = X'.ofRestrict (X'.openOf U') ≫ φ
A morphism
φ : X' ⟶ XofK-analytic spaces is a local analytic isomorphism when every point ofX'has an open neighbourhoodU'whichφmaps isomorphically onto an open subspaceX|_VofX: an isomorphismχ : X'|_{U'} ≅ X|_Vwithχ ≫ (X|_V → X) = (X'|_{U'} → X') ≫ φ. These are the local analytic isomorphisms of [Wlo09, Theorem 2.0.1 (3)] (Kollár's étale morphisms, the smooth morphisms of relative dimension zero [Kol07, Theorem 45 (5)]): open immersions, isomorphisms, covering maps and the morphism∐ Uᵢ → Xfrom the disjoint union of an open cover, injective or not. -
structuredefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
structure ResolutionAssignment.LiftsLocalIsomorphisms {K : Type} [RCLike K] {C : Type w} [HasUnderlyingSpace C K] (R : ResolutionAssignment C) : Prop
structure ResolutionAssignment.LiftsLocalIsomorphisms {K : Type} [RCLike K] {C : Type w} [HasUnderlyingSpace C K] (R : ResolutionAssignment C) : Prop
A resolution assignment
Ron the inputsClifts local analytic isomorphisms, in two forms. Every isomorphismφ : X|_U → Y|_Vbetween open subspaces of two inputs lifts to exactly one morphismψ : R(X)|_{Π_X⁻¹ U} → R(Y)|_{Π_Y⁻¹ V}overφ,ψ ≫ Π_Y|_V = Π_X|_U ≫ φ, whereΠ_X|_U : R(X)|_{Π_X⁻¹ U} → X|_Uis the restriction ofΠ_X(composition in diagrammatic order), andψis an isomorphism. And every local analytic isomorphismφ : X' → Xbetween inputs (Hom.IsLocalIso) lifts to exactly one morphismψ : R(X') → R(X)overφ,ψ ≫ Π_X = Π_{X'} ≫ φ, andψis a local analytic isomorphism. Over every openU' ⊆ X'whichφmaps isomorphically onto an open subspaceX|_V, the lift ofφrestricts to the lift of that isomorphism, by the uniqueness of the latter (LiftsLocalIsomorphisms.lift_restrict). By the uniqueness the lifts respect identities and composition, soRis a functor on the groupoid of isomorphisms between open subspaces of inputs and on the local analytic isomorphisms between inputs.Fields
exists_lift_of_isIso : ∀ (X Y : C) (U : Set ↑↑(toAnalyticSpace X).toPresheafedSpace) (V : Set ↑↑(toAnalyticSpace Y).toPresheafedSpace), IsOpen U → IsOpen V → ∀ (φ : (toAnalyticSpace X).restrictSet U ⟶ (toAnalyticSpace Y).restrictSet V), CategoryTheory.IsIso φ → ∃ ψ, CategoryTheory.IsIso ψ ∧ ∀ (ψ' : (R.space X).restrictSet (↑(R.map X) ⁻¹' U) ⟶ (R.space Y).restrictSet (↑(R.map Y) ⁻¹' V)), ψ' ≫ Hom.restrictSet (R.map Y) V = Hom.restrictSet (R.map X) U ≫ φ ↔ ψ' = ψ
Every isomorphism between open subspaces of two inputs lifts to exactly one morphism of the resolutions over it, an isomorphism.
exists_lift_of_isLocalIso : ∀ (X' X : C) (φ : toAnalyticSpace X' ⟶ toAnalyticSpace X), Hom.IsLocalIso φ → ∃ ψ, Hom.IsLocalIso ψ ∧ ∀ (ψ' : R.space X' ⟶ R.space X), ψ' ≫ R.map X = R.map X' ≫ φ ↔ ψ' = ψ
Every local analytic isomorphism between inputs lifts to exactly one morphism of the resolutions over it, a local analytic isomorphism.
The inputs: reduced spaces.
The reduced K-analytic spaces, as a full subcategory of the K-analytic spaces
(ReducedSpace, the counterpart of Definition 4.2.6.1), are the inputs of the
resolution of analytic spaces. Kollár states the theorem for every separable analytic space; his
notion of resolution is stated for varieties, and his proofs are for reduced spaces, extended to
reducible ones. A non-reduced space X is resolved through its reduction: the resolution of
X_{\mathrm{red}} followed by the closed immersion X_{\mathrm{red}} \to X.
Lean code for Definition4.3.5.4●1 definition
Associated Lean declarations
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ReducedSpace[complete]
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ReducedSpace[complete]
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abbrevdefined in Hironaka/AnalyticSpace/Resolution/Defs.leancomplete
abbrev ReducedSpace (K : Type) [RCLike K] : Type (u + 1) := CategoryTheory.ObjectProperty.FullSubcategory fun X => X.IsReduced
abbrev ReducedSpace (K : Type) [RCLike K] : Type (u + 1) := CategoryTheory.ObjectProperty.FullSubcategory fun X => X.IsReduced
The inputs of the resolution theorem: the reduced
K-analytic spaces, as a full subcategory of theK-analytic spaces. An objectXhasX.obj : AnalyticSpace K, its underlying space (toAnalyticSpace X).
For K = \mathbb{R} or \mathbb{C} there is a resolution assignment
X \mapsto (\Pi_X \colon R(X) \to X) on the reduced K-analytic spaces
(Definition 4.3.5.4, Definition 3.3.4.1) such that for every input
X:
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R(X)is non-singular; -
\Pi_Xis an isomorphism over the simple points ofX; -
\Pi_X^{-1}(\operatorname{Sing} X)is the support of a simple normal crossings divisor; -
\Pi_Xis proper and bimeromorphic onto its image, and the image of\Pi_Xis the closure of the simple points; over every relatively compact open subset ofX,\Pi_Xis a finite composite of blow-ups of smooth centres of an ambient manifold restricted to strict transforms; -
every analytic isomorphism between open subspaces of two inputs lifts to exactly one morphism of the resolutions over it, an isomorphism, and every local analytic isomorphism
\varphi \colon X' \to Xbetween inputs lifts to exactly one morphismR(X') \to R(X)over it, itself a local analytic isomorphism, which restricts over every open on which\varphiis injective to the lift of the isomorphism of open subspaces.
This is resolution of singularities for analytic spaces, functorial for local analytic
isomorphisms: the lifts are unique, so they respect identities and composition, and the resolution
is local on the space. Kollár's condition (5) asks more, the commutation with all smooth morphisms;
the lifting of local analytic isomorphisms is its case of étale morphisms and is
[Wlo09, Theorem 2.0.1 (3)]. Conditions (1)–(3), with properness, bimeromorphy and the image
clause, are Hom.IsStrongResolutionOntoClosureRegularLocus
(Definition 4.3.5.1), condition (4) is
Hom.IsLocallyFiniteAmbientBlowUpComposite (Definition 4.3.5.2), and
condition 5 is
ResolutionAssignment.LiftsLocalIsomorphisms (Definition 4.3.5.3).
The bimeromorphy follows from (2) and (3): the preimage of the simple locus is the complement of
the support of a simple normal crossings divisor, hence dense.
Analytic spaces, their morphisms, simple points and closed subspaces are in the chapter Analytic spaces: Definition 3.3.3.1, Definition 3.3.3.2, Definition 3.3.3.3, Definition 3.3.4.1.
Lean code for Theorem4.3.5.5●1 theorem
Associated Lean declarations
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exists_functorial_resolution[complete]
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exists_functorial_resolution[complete]
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theoremdefined in Hironaka/Resolution/Analytic/Kol07Thm45/ResolutionAssembly.leancomplete
theorem exists_functorial_resolution (K : Type) [RCLike K] : ∃ R, (∀ (X : ReducedSpace K), Hom.IsStrongResolutionOntoClosureRegularLocus (R.map X) ∧ Hom.IsLocallyFiniteAmbientBlowUpComposite (R.map X)) ∧ R.LiftsLocalIsomorphisms
theorem exists_functorial_resolution (K : Type) [RCLike K] : ∃ R, (∀ (X : ReducedSpace K), Hom.IsStrongResolutionOntoClosureRegularLocus (R.map X) ∧ Hom.IsLocallyFiniteAmbientBlowUpComposite (R.map X)) ∧ R.LiftsLocalIsomorphisms
Resolution of analytic spaces [Kol07, Theorem 45]; [Wlo09, Theorem 2.0.1], over
K = ℝorK = ℂ. There is a resolution assignmentX ↦ (Π_X : R(X) → X)on the reducedK-analytic spaces (ResolutionAssignment (ReducedSpace K)) such that-
every
Π_Xis a strong resolution ofXonto the closure of its simple locus (Hom.IsStrongResolutionOntoClosureRegularLocus):Π_Xis proper and bimeromorphic onto its image, (1)R(X)is non-singular, (2)Π_Xis an isomorphism over the simple locusX.regularLocus, (3)Π_X⁻¹(X.singularLocus)is the support of a simple normal crossing divisor ofR(X), and the image ofΠ_Xis the closure ofX.regularLocus(in neither source; see the relation to the source below); -
(4) over every relatively compact open subset of
Xthe morphismΠ_Xis the composite of a finite sequence of blow-ups of smooth centres of an ambient manifold, restricted to strict transforms (Hom.IsLocallyFiniteAmbientBlowUpComposite); -
(5)
Rlifts local analytic isomorphisms (ResolutionAssignment.LiftsLocalIsomorphisms): every isomorphism between open subspaces of two inputs lifts to exactly one morphism between their preimages in the resolutions over it, an isomorphism; and every local analytic isomorphismφ : X' → Xbetween inputs (Hom.IsLocalIso: locally an isomorphism onto an open subspace, injective or not) lifts to exactly one morphismR(X') → R(X)over it, itself a local analytic isomorphism ([Wlo09, Theorem 2.0.1 (3)]). Over every open on whichφis injective, the lift ofφrestricts to the lift of the isomorphism of open subspaces (ResolutionAssignment.LiftsLocalIsomorphisms.lift_restrict).
Kollár's (4), "
Π_Xis projective over any compact subset ofX", is split between the properness ofHom.IsResolutionand the factorization clause, whose ambient manifold is the disjoint union of finitely many opens ofKⁿ, one per piece of a finite open cover of the relatively compact open, with the identification withΠ_Xgiven piecewise. The non-singularity ofR(X)is repeated by (3), sinceClosedSubspace.IsSncBoundaryasks for a regular system of parameters at every point ofR(X).Source statement: [Kol07, Theorem 45]
Source statement: [Wlo09, Theorem 2.0.1]
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An embedded desingularization functor for closed subspaces of manifolds (the order-reduction
algorithm applied to the ideal of the subspace in every dimension, functorial under local analytic
isomorphisms and compatible with closed embeddings of the ambient manifolds) is applied to local
embeddings of the reduced space into manifolds. The resolutions of the pieces are independent of
the embedding chosen and glue over the exhaustion of the space by relatively compact opens to
R(X); the conditions are read off the properties of the functor, the lifting of condition (5)
from its functoriality. The lift of an isomorphism between open subspaces is the only morphism over
it, because two morphisms out of a non-singular open part of R(X) over the same morphism agree
over the simple locus, where the resolutions are isomorphisms, a dense open subset. The lifting of
local analytic isomorphisms follows: the lifts over the opens on which \varphi is injective
agree on the overlaps by the same rigidity, and glue.
4.3.6. Resolution of a reduced complex-analytic space
Let X be a reduced complex-analytic space. Then there is a morphism \pi \colon R \to X such
that
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Ris non-singular; -
\piis an isomorphism over the simple points ofX; -
\pi^{-1}(\operatorname{Sing} X)is the support of a simple normal crossings divisor; -
\piis proper and bimeromorphic onto its image and, over every relatively compact open subset ofX, a finite composite of blow-ups of smooth centres of an ambient manifold restricted to strict transforms; -
\piis surjective.
This is resolution of singularities for a single reduced complex space, without the functoriality
of the resolution of analytic spaces (Theorem 4.3.5.5). Conditions (1)–(3), with properness
and bimeromorphy, are Hom.IsStrongResolution (Definition 4.3.5.1), and (4) is
Hom.IsLocallyFiniteAmbientBlowUpComposite (Definition 4.3.5.2).
Lean code for Theorem4.3.6.1●1 theorem
Associated Lean declarations
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theoremdefined in Hironaka/Resolution/Analytic/Kol07Thm45/ResolutionAssembly.leancomplete
theorem exists_surjective_resolution_of_isReduced (X : AnalyticSpace ℂ) (hX : X.IsReduced) : ∃ R π, Hom.IsStrongResolution π ∧ Hom.IsLocallyFiniteAmbientBlowUpComposite π ∧ Function.Surjective ↑π
theorem exists_surjective_resolution_of_isReduced (X : AnalyticSpace ℂ) (hX : X.IsReduced) : ∃ R π, Hom.IsStrongResolution π ∧ Hom.IsLocallyFiniteAmbientBlowUpComposite π ∧ Function.Surjective ↑π
Resolution of a reduced complex-analytic space [Kol07, Theorem 45 (1)–(4)]; [Wlo09, Theorem 2.0.1], for
K = ℂ. LetXbe a reduced complex-analytic space. Then there is a morphismπ : R → Xsuch that-
πis a strong resolution ofX(Hom.IsStrongResolution):πis proper and bimeromorphic onto its image, and (1)Ris non-singular; (2)πis an isomorphism over the simple locusX.regularLocus; (3)π⁻¹(X.singularLocus)is the support of a simple normal crossing divisor ofR; -
(4) over every relatively compact open subset of
X,πis the composite of a finite sequence of blow-ups of smooth centres of an ambient manifold, restricted to strict transforms (Hom.IsLocallyFiniteAmbientBlowUpComposite); -
πis surjective.
Source statement: [Kol07, Theorem 45 (1)–(4)]
Source statement: [Wlo09, Theorem 2.0.1] (surjectivity from the density of the simple locus over ℂ)
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The specialization of Theorem 4.3.5.5 to K = \mathbb{C}: its conditions (1)–(4) are
taken as they stand, its condition on the image, \operatorname{range} \pi = \overline{X^{ns}},
becomes surjectivity because the simple locus of a reduced complex space is dense, and the lifting
condition (5) is dropped.