Ideal sheaves along an analytic isomorphism across the models #
The second layer of the model transport (Hironaka/Resolution/Analytic/ModelTransport/). An
analytic isomorphism g : N ≃ M between manifolds modelled on E' and E — for the main theorems
the identity M.transport ψ → M of Hironaka/Resolution/Analytic/ModelTransport/Manifold.lean and
the identities of its open subsets — carries every stalk-level notion of the analytic main
theorems from M to N:
- the germ map
𝒪_{M, g b} → 𝒪_{N, b}is bijective at a local analytic isomorphism, whatever the two models (germMap_bijective_of_isLocalDiffeomorphAt', the two-model form of the lemma ofHironaka/Manifold/IdealSheaf/DerivLocality.lean), so it is a ring isomorphism of the stalks (Diffeomorph.stalkRingEquiv); - the pull-back
pullbackDiffeomorph g J := J.pullback g(IdealSheaf.pullback, which takes two models) has stalks the images of the stalks (stalkIdeal_pullbackDiffeomorph), support the preimage of the support, respects⊤,⊥and products, is inverted by the pull-back alongg⁻¹and hence injective, and transports the pull-back along an analytic map across a squaref ∘ g' = g ∘ f'(IsModelSquare,pullbackDiffeomorph_comap); - the predicates of the vocabulary read on the stalks —
IsNonzeroEverywhere,IsNonsingular,IsReduced,IsInvertible,HasOnlyNormalCrossingsWithandHasOnlyNormalCrossings(Hironaka's normal crossings at the stalk, [Hir64, Definition 2, p. 141]),IsNormalCrossingsDivisor(Bierstone–Milman's normal-crossings divisor, [BM97, Theorem 1.10]),ord— hold for the pull-back iff they hold for the ideal sheaf: each is a ring-theoretic statement about a stalk, carried by the stalk isomorphism (IsLocalRing.map_ringEquiv_maximalIdeal,ringKrullDim_eq_of_ringEquiv,Ideal.quotientEquiv,IsRegularLocalRing.of_ringEquiv,Ideal.IsRadical.comap,Ideal.comap_minimalPrimes_eq_of_surjective), and the points correspond underg; the simple locusregularLocusof the pull-back is the preimage of the simple locus (regularLocus_pullbackDiffeomorph); IdealSheaf.transport ψ J: an ideal sheaf onMread onM.transport ψ.
The pointwise bodies of HasOnlyNormalCrossingsWith and IsNormalCrossingsDivisor are transported
on the ring side (exists_regularSystem_normalCrossings_map, exists_regularSystem_monomial_map);
the two directions of each iff are the lemma at the stalk isomorphism and at its inverse. These are
chart-independence statements: the predicates of the vocabulary are defined on stalks and see no
coordinates.
The germ map of a local analytic isomorphism across the models is bijective: the germ map
of a local inverse is a two-sided inverse (germMap_bijective_of_isLocalDiffeomorphAt of
Hironaka/Manifold/IdealSheaf/DerivLocality.lean with the two models free; the same proof, the
models only in its binders).
Ideals along a ring isomorphism #
The minimal primes of the image of an ideal under a ring isomorphism are the images of its
minimal primes (Ideal.comap_minimalPrimes_eq_of_surjective along the inverse).
The pointwise body of HasOnlyNormalCrossingsWith (Hironaka's normal crossings at the stalk,
[Hir64, Definition 2, p. 141]: a regular system of parameters containing an equation of each
minimal prime of I and equations for J) transports along a ring isomorphism of the stalks: the
image of a regular system is a regular system (IsLocalRing.map_ringEquiv_maximalIdeal,
ringKrullDim_eq_of_ringEquiv), the minimal primes correspond (minimalPrimes_map_ringEquiv).
The pointwise body of IsNormalCrossingsDivisor (Bierstone–Milman's normal-crossings divisor
at the stalk, [BM97, Theorem 1.10]: a monomial in a regular system of parameters) transports along
a ring isomorphism of the stalks.
The pull-back along an analytic isomorphism across the models #
The stalk isomorphism 𝒪_{M, g b} ≃+* 𝒪_{N, b} of an analytic isomorphism across the
models: its germ map, bijective by germMap_bijective_of_isLocalDiffeomorphAt'.
Equations
- g.stalkRingEquiv b = RingEquiv.ofBijective (Manifold.germMap ⇑g ⋯ b) ⋯
Instances For
The stalk isomorphism is the germ map on points.
The pull-back of an ideal sheaf along an analytic isomorphism across the models
(IdealSheaf.pullback, which takes two models).
Equations
Instances For
The stalk of the pull-back is the image of the stalk under the stalk isomorphism.
The support of the pull-back is the preimage of the support.
The unit ideal pulls back to the unit ideal.
The pull-back of a product is the product of the pull-backs.
The zero ideal sheaf pulls back to the zero ideal sheaf.
Pulling back along g and then along g⁻¹ is the identity.
The pull-back along an analytic isomorphism is injective.
The square f ∘ g' = g ∘ f' of two analytic isomorphisms across the models and two analytic
maps: the hypothesis of the transport lemmas of
Hironaka/Resolution/Analytic/ModelTransport/Square.lean and SquareChart.lean.
Equations
- Hironaka.Manifold.IsModelSquare g g' f f' = ∀ (x : N'.carrier), f (g' x) = g (f' x)
Instances For
The pull-back along an analytic map (comap) transports along a square of analytic
isomorphisms across the models.
IsNonzeroEverywhere along the isomorphism.
IsNonsingular (the regularity of the local rings 𝒪_x / J_x) along the isomorphism: the
quotients are isomorphic rings (Ideal.quotientEquiv, IsRegularLocalRing.of_ringEquiv).
The simple locus regularLocus along the isomorphism, the pointwise form of
isNonsingular_pullbackDiffeomorph_iff: the quotients 𝒪_b / (g^*J)_b and 𝒪_{g b} / J_{g b} are
isomorphic rings.
IsReduced along the isomorphism (Ideal.IsRadical.comap).
IsInvertible along the isomorphism: the generating non-zero-divisor is carried by the stalk
isomorphism.
HasOnlyNormalCrossingsWith along the isomorphism.
HasOnlyNormalCrossings along the isomorphism.
IsNormalCrossingsDivisor along the isomorphism.
The order along the isomorphism (ord_pullback_of_isLocalDiffeomorphAt, which takes two
models).
An ideal sheaf on M read on the re-modelled M: the same sections, pulled back along the
identity M.transport ψ → M.