The chaining of the closed-embedding commutation, III: the chaining lemma #
[Kol07, 108] reduces the commutation of the order-reduction functors with closed embeddings to
the hypersurface case along a flag Y = Y₀ ⊂ Y₁ ⊂ ⋯ ⊂ Y_c = X, the question being local. This
module proves the step of that reduction, (E1): if B₂ commutes with closed embeddings of
codimension s through B₁ and B₁ with hypersurfaces through B₀, then B₂ commutes with
closed embeddings of codimension s + 1 through B₀; and the induction it drives, (E3), for a
tower of functors at the standard models. The sources say only that the question is local; the
route through a flag cover is spelled out here:
- (E-a), (E-b)
IsClosedSubmanifold.diffeomorphRestrict,BlowUpSequence.pushforward_pullback_diffeomorph: an analytic isomorphism of the ambient manifolds carrying one closed submanifold onto another restricts to an isomorphism of the bundled submanifolds, and push-forward ([Kol07, Definition 30, 30.3]) commutes with the pull-back along it (pushforwardAux_pullbackat the trivial stages); - (E-c)
BlowUpSequence.pushforwardRestrict_pushforwardRestrict_of_flag: the per-open form ofpushforward_pushforward_of_flag(Hironaka.Resolution.Analytic.Restrict.FlagPushforward): pushing a list forward fromS ∩ UtoY ∩ Uand then toUis pushing it forward fromS ∩ UtoU, the list read on theS ⊂ Ystructure through the identificatione; - the flag case
AnalyticFamilyFunctor.commutesWithClosedEmbeddings_flag_case: on a manifold carrying a global flagS ⊂ Y ⊂ M, the codimension-sclause atY(C), the hypersurface clause of the middle functor atS ⊂ Y(D) and (E-c) give the per-open identity atS; the ideals are handled byHironaka.Resolution.Analytic.Submanifold.FlagIdeal; - (E1)
AnalyticFamilyFunctor.commutesWithClosedEmbeddingsOfEmptyDivisorFam_chain: a relatively compact openUhas a flag cover (FlagCover,Hironaka.Resolution.Analytic.Functor.ChainClosedEmbeddingCover); on its coproductΣthe preimage ofSsits in a global flag, pull-back along the surjective local isomorphismcoverMapis injective ([Kol07, Proposition 37]), both sides of the identity pull back to values of the functors on the pulled-back triples (CommutesWithLocalIsos;pushforwardRestrict_pullback_restrictMapfor the right side), and the flag case onΣidentifies them; - (E3)
AnalyticFamilyFunctor.commutesWithClosedEmbeddingsOfEmptyDivisorFam_tower: induction on the codimension with (E1) at the bottom of the flag and the degenerate case ofHironaka.Resolution.Analytic.Functor.ChainClosedEmbeddingDegeneratewhenn ≤ s.
(E-a) an ambient analytic isomorphism carrying one closed submanifold onto another induces #
an analytic isomorphism of the bundled submanifolds
G maps SA = G⁻¹(SB) into SB.
G.symm maps SB into SA = G⁻¹(SB).
The restriction of G to the bundled submanifolds.
Equations
- Manifold.IsClosedSubmanifold.restrictMapOfPreimage G hA hB h = hA.restrictMap hB ⇑G ⋯ ⋯
Instances For
The restriction of G.symm to the bundled submanifolds.
Equations
- Manifold.IsClosedSubmanifold.restrictMapOfPreimageSymm G hA hB h = hB.restrictMap hA ⇑G.symm ⋯ ⋯
Instances For
An analytic isomorphism G : A ≃ B with SA = G⁻¹(SB) restricts to an analytic isomorphism
of the bundled closed submanifolds (both directions IsClosedSubmanifold.restrictMaps, inverse to
each other on the carriers).
Equations
- One or more equations did not get rendered due to their size.
Instances For
The restricted isomorphism is G on the points.
(E-b) the square: push-forward against pull-back along an ambient isomorphism #
[Kol07, Definition 30, 30.3] transported along an analytic isomorphism of the ambient
manifolds (the square lemma pushforwardAux_pullback at the trivial stages): pulling back the
push-forward along G is pushing forward the pull-back along the induced isomorphism of the
bundled submanifolds.
Three pull-backs against two: two chains of local analytic isomorphisms with the same
composite pull a list back to the same list (pullback_comp twice each way, pullback_congr
in the middle).
(E-c) the composition of the per-open push-forwards along the flag #
The identification of the two bundled structures on S maps the trace of U on S ⊂ Y into
the trace of U on S.
The identification of the two bundled structures on S maps the trace of U on S ⊂ Y ONTO
the trace of U on S.
The trace of S on the open U is a hypersurface of the trace of Y (the flag restricted to
U; preimage_val_of_subset at codimension s + 1 - s = 1).
The trace of S ∩ U in the restricted flag is the preimage, under the bridge of Y, of the
trace of S in Y ∩ U_Y (a set-level identity of the two bundled hypersurfaces).
f₁: the identification e restricted to the traces of U.
Equations
- hY.flagMapS hS hSY e he U = Hironaka.Manifold.AnalyticMap.restrictMap ⟨⇑e, ⋯⟩ (hSY.preimageOpens (hY.preimageOpens U)) (hS.preimageOpens U) ⋯
Instances For
f₁ is a local analytic isomorphism (e restricted to opens).
f₂: the bridge of S ⊂ Y at U_Y, inverted.
Equations
- hY.flagBridgeSY hSY U = ⟨⇑(hSY.restrictBundleDiffeomorph (hY.preimageOpens U)).symm, ⋯⟩
Instances For
f₃: the isomorphism of the two bundled hypersurfaces S ∩ U induced by the bridge of Y.
Equations
- hY.flagBridgeHyp hS hsub hSY U = ⟨⇑(Manifold.IsClosedSubmanifold.diffeomorphRestrict (hY.restrictBundleDiffeomorph U).symm ⋯ ⋯ ⋯), ⋯⟩
Instances For
g₁: the bridge of S at U, inverted.
Equations
- hS.flagBridgeS U = ⟨⇑(hS.restrictBundleDiffeomorph U).symm, ⋯⟩
Instances For
f₂ is a local analytic isomorphism (an inverted bridge).
f₃ is a local analytic isomorphism (diffeomorphRestrict).
g₁ is a local analytic isomorphism (an inverted bridge).
(E), the restricted form of pushforward_pushforward_of_flag ([Kol07, Definition 30, 30.3]
twice): pushing a list forward from the hypersurface S ∩ U of Y ∩ U to Y ∩ U and then to U
is pushing it forward from S ∩ U to U — the list read on the S ⊂ Y structure through e.
From the unrestricted lemma on
M.restrict U, the three pushforwardRestricts unfolded by
pushforwardRestrictOf_eq, the middle push-forward transported along the bridge of Y by
pushforward_pullback_diffeomorph, and the pull-backs composed (pullback_comp, pullback_congr:
all the maps are the identity on the points of S ∩ U).
The pull-back of an empty-divisor triple #
The pull-back of an empty-divisor triple along a local analytic isomorphism is the
empty-divisor triple of the pulled-back ideal (HypersurfaceFamily.empty_comap).
The flag cover: the descent map restricted to the bundled preimage of S #
The descent map restricted to the bundled preimage of S
(IsClosedSubmanifold.restrictMap).
Equations
- C.descS = ⋯.restrictMap hS ⇑C.desc ⋯ ⋯
Instances For
The restricted descent map is a local analytic isomorphism (isLocalDiffeomorph_restrictMap at
any codimension).
The restricted descent map carries the trace of the cover's opens on the preimage of S ONTO
the trace of U on S (the cover's opens map onto U).
The flag case of the chaining lemma: (C) + (D) + (E) #
The flag case of (E1) ([Kol07, 108]): on a manifold
carrying a global flag S ⊂ Y ⊂ M (Y of codimension s, S a hypersurface of Y), the
per-open identity of the predicate at S follows from the codimension-s clause at Y (C), the
codimension-one clause of the middle functor at S ⊂ Y (D) and the composition of the two
push-forwards (E).
(E1) the chaining lemma and (E3) the tower #
(E1), the chaining lemma ([Kol07, 108]):
the codimension-s clause of B₂ through B₁ and the codimension-one clause of B₁ through B₀
give the codimension-(s + 1) clause of B₂ through B₀. (A) a flag cover of the relatively
compact open U and its coproduct Σ, on which desc⁻¹ S sits in the global flag
FlagCover.flag of codimension s; pull-back along the surjective local isomorphism coverMap
is injective ([Kol07, Proposition 37]), so it suffices to compare the two pull-backs: (A1) the left
side is the value of B₂ on the pulled-back triple (CommutesWithLocalIsos), (A2) the right side
is the push-forward from desc⁻¹ S of the value of B₀ on the pulled-back triple
(pushforwardRestrict_pullback_restrictMap, CommutesWithLocalIsos along the restricted descent
map), and the flag case (C)–(E) on Σ identifies the two.
(E3): for a tower F of family functors at
the standard models with the domain hypotheses of (E1) at every level, the codimension-zero and
codimension-one clauses give the clause at every codimension, n - s literal — induction on s
with (E1) at the bottom of the flag when 0 < n - s and the degenerate case of
Hironaka.Resolution.Analytic.Functor.ChainClosedEmbeddingDegenerate when n ≤ s.