Hironaka's clauses (i)–(iv) on the resolution family #
The dictionary between Kollár's smooth blow-up sequence of order ≥ m for a marked ideal (Kol07,
Definition 66; the field isOfOrderGe of BOanFam, on the marked transforms) and the clauses
(i)–(iv) of Hironaka's Main Theorem II′(N) [Hir64, p. 156] on the value resolveSeqOn bo T U hU of
the resolution family (Hironaka/Resolution/Analytic/Wlo09/Rounds.lean): the rounds
BO_{n,d}, …, BO_{n,1} of [Hir64, Main Theorem II(N), p. 176] with the empty blow-ups erased.
The dictionary on one round #
BOanFam.isOfOrder_seqOn: the value ofB : BOanFam 𝕜 n mon a triple of its class over a relatively compact open is a sequence of order exactlymon the weak transforms (isOfOrder_of_isOfOrderGe_of_ord_le; [Kol07, Remark 67]: along a sequence of order≥ mstarting withmax-ord I = m, every blow-up has order exactlym);BOanFam.markedTransformSeq_seqOn_eq_weakTransformSeq: along the round the marked transform is the weak transform (Kollár's birational transform of(I, m)whenord_Z I = m, [Kol07, Definition 48]; Hironaka's weak transform, [Hir64, p. 142]);BOanFam.ord_weakTransformSeq_seqOn_eq_of_mem_center: the order of the weak transform ismat every point of every centre (clause (2) of [Hir64, Main Theorem II(N), p. 176]).FiniteSuccession.IsOfOrder.ord_weakTransformSeq_eq_of_mem_center(the pointwise form on any succession:≥from the order along the centre,≤from [Kol07, Lemma 61] iterated) andFiniteSuccession.center_isNonsingular(clause (i): every centre is the ideal sheaf of a closed submanifold, hence non-singular).
Clause (ii) in Hironaka's weak spelling #
FiniteSuccession.HasConstantPositiveOrderAlongCenters S J(Hironaka/Manifold/Resolution/Defs.lean): at every stage the order of the weak transform ofJis a positive constant on the centre, clause (ii) as a predicate;hasConstantPositiveOrderAlongCenters_nil,hasConstantPositiveOrderAlongCenters_cons_iff,IsOfOrder.hasConstantPositiveOrderAlongCenters(a round satisfies it with the constantm), and the transports along a concatenation, a pull-back along any local analytic isomorphism (the weak transform's exponent is the generic order along the component through the point, which a local isomorphism preserves; no surjectivity is needed), a diffeomorphism and the deletion of the empty blow-ups (hasConstantPositiveOrderAlongCenters_{concat,pullback,map,eraseEmpty}).hasConstantPositiveOrderAlongCenters_resolveFrom, the invariant of the recursionresolveFrom(on the pattern ofcentersOver_resolveFrom,Hironaka/Resolution/Analytic/Wlo09/CentersOver.lean): the round pulled back along the corestriction ofι, the junction identity (the head's last weak transform ofι^* 𝓘is the pull-back alongpullbackLiftLastof the derived ideal, the weak transform being the marked transform at the round's mark) and the induction hypothesis on the derived triple;hasConstantPositiveOrderAlongCenters_resolveSeqOnat the canonical chain, through the erasure.
Clauses (iii) and (iv) #
- Clause (iii) is the first conjunct of
isOfOrderGe_zero_resolveSeqOn(Hironaka/Resolution/Analytic/Wlo09/Monomial.lean, clause (3′) of [Kol07, Definition 66] for the erased value) read through the identificationrestrictTriple_F_idealSheafof the restricted triple's boundary ideal sheaf (idealSheaf_comap_of_isSncat the inclusion);center_resolveSeqOn_hasSncWithis its family form, a corollary throughhasSncWith_totalTransformSeqFrom_center_of_forall_lt. - The first half of clause (iv):
FiniteSuccession.hasOnlyNormalCrossings_boundarySeq_last_of_isOfOrderGe_zero(along a sequence of order≥ 0for(I, 0, red F)withFa simple normal crossing family, the last boundary has only normal crossings:isSnc_totalTransformSeqFrom_and_boundarySeq_eq_of_forall_ltthenhasOnlyNormalCrossings_idealSheaf), atisOfOrderGe_zero_resolveSeqOn. Hironaka remarks that this half follows from (iii) (the remark after [Hir64, Main Theorem II, p. 143]). - The second half of clause (iv):
weakTransformSeq_last_eq_top_{concat,pullback,eraseEmpty}(the transports of the statement that the last weak transform is the unit ideal),weakTransformSeq_last_resolveFrom_eq_top(the exit of the recursion in the weak spelling: atd = 0the list is empty andcur.I = ⊤fromord ≤ 0; clause (1) of [Kol07, Theorem 68] at the last round's mark1) andweakTransformSeq_last_resolveSeqOn_eq_top.
Restatements #
The last section restates the clauses under the names resolveSeqOn_clause_ii,
resolveSeqOn_clause_iii and resolveSeqOn_boundarySeq_last_hasOnlyNormalCrossings. Each docstring
says which theorem it restates and how the predicate is unfolded;
Hironaka/Resolution/Analytic/Wlo09/HironakaAssembly.lean uses resolveSeqOn_clause_ii, and the
other two are not used elsewhere.
The empty succession satisfies clause (ii).
The constructor form (the analogue of isOfOrderGe_cons_iff): the head clause on Y for J
and the tail for the weak transform of J along the head.
The pointwise form of the round dictionary: along a sequence of order exactly m with ord I ≤ m everywhere, the weak transform has order m at every point of every centre (≥ from the order
along the centre, ≤ from [Kol07, Lemma 61] iterated).
The round dictionary on any succession: Hironaka's sequence of order exactly m ≥ 1 with
ord I ≤ m everywhere satisfies clause (ii) with the constant m (IsOfOrder.ordAlong_eq,
ordAlongIdeal_le_ord_of_mem_support, ord_markedTransformSeq_le through
IsOfOrder.markedTransformSeq_eq_weakTransformSeq).
Clause (i) of [Hir64, Main Theorem II′(N), p. 156]: every centre of a finite succession is
non-singular (idealSheaf_center and isNonsingular_idealSheaf).
The first half of clause (iv) of [Hir64, Main Theorem II′(N), p. 156], in general form (Hironaka
remarks after Main Theorem II, p. 143, that it follows from (iii)): along a succession of order
≥ 0 for (I, 0, red F) with F a simple normal crossing family, that is, under clause (3′) of
[Kol07, Definition 66] alone, the last boundary has only normal crossings
(isSnc_totalTransformSeqFrom_and_boundarySeq_eq_of_forall_lt and
hasOnlyNormalCrossings_idealSheaf).
Clause (ii) along a concatenation (the analogue of isOfOrderGe_concat): the tail starts at the
head's last weak transform.
Clause (ii) pulls back along any local analytic isomorphism, surjective or not
(center_pullback, weakTransformSeq_pullback, ord_comap_of_isLocalDiffeomorphAt at the lifts).
Clause (ii) transports along a diffeomorphism (map_eq_pullback_symm,
hasConstantPositiveOrderAlongCenters_pullback, comap_comap_symm).
Clause (ii) survives the deletion of the empty blow-ups ([Kol07, 34.1]; the pattern of
isOfOrderGe_eraseEmpty: a kept step by hasConstantPositiveOrderAlongCenters_cons_iff, a
deleted step by hasConstantPositiveOrderAlongCenters_map along emptyBlowUpDiffeomorph with
weakTransform_blowUpπ_of_eq_empty).
No boundary is involved, so no simple-normal-crossings hypothesis.
The last weak transform is the unit ideal along a concatenation, from the tail started at the
head's last weak transform (stated as a transport of the proposition, so no cast across
stage_last_concat).
The same along a pull-back (weakTransformSeq_pullback at the last stage, comap ⊤ = ⊤).
The same after the deletion of the empty blow-ups (weakTransformSeq_last_eraseEmpty).
The value of B on a triple of its class over a relatively compact open is a sequence of order
exactly m ([Kol07, Remark 67]): isOfOrder_of_isOfOrderGe_of_ord_le on the field B.isOfOrderGe
with the class bound restricted to U (ord_comap_of_isLocalDiffeomorphAt).
Along the value of B the marked transform at mark m is the weak transform: Kollár's
birational transform of (I, m) coincides with the unmarked one when ord_Z I = m (Kol07,
Definition 48), and that is Hironaka's weak transform ([Hir64, p. 142]).
Along the value of B the weak transform has order m at every point of every centre (clause
(2) of [Hir64, Main Theorem II(N), p. 176]).
The restricted triple's boundary ideal sheaf is the restriction of the boundary ideal sheaf
(HypersurfaceFamily.idealSheaf_comap_of_isSnc at the inclusion).
The invariant of the recursion resolveFrom for clause (ii) (Hir64, Main Theorem II′(N),
p. 156, (ii) round by round, on the pattern of centersOver_resolveFrom): the round pulled back
along the corestriction of ι by hasConstantPositiveOrderAlongCenters_pullback and
IsOfOrder.hasConstantPositiveOrderAlongCenters (AnalyticTriple.isOfOrderGe_pullback,
isOfOrder_of_isOfOrderGe_of_ord_le with the class bound transported), the tail by the induction
hypothesis on the derived triple with the junction identity (the head's last weak transform of
ι^* cur.I is the pull-back along pullbackLiftLast of the derived ideal:
markedTransformSeq_seqOn_eq_weakTransformSeq at the round,
markedTransformSeq_last_pullbackLiftLast), glued by
hasConstantPositiveOrderAlongCenters_concat.
The invariant of the recursion resolveFrom for the second half of clause (iv), in the weak
spelling ([Hir64, Main Theorem II′(N), p. 156, (iv)]; clause (1) of [Kol07, Theorem 68] at the
last round's mark 1): the last weak transform of ι^* cur.I along the rounds from d is the
unit ideal. The recursion of hasConstantPositiveOrderAlongCenters_resolveFrom with
weakTransformSeq_last_eq_top_concat and weakTransformSeq_last_eq_top_pullback at the junction;
at d = 0 the list is empty and cur.I = ⊤ from ∀ x, ord x ≤ 0, the same exit as inside
pullbackIsMonomialAtLast_resolveFrom.
Clause (ii) for the value resolveSeqOn bo T U hU:
hasConstantPositiveOrderAlongCenters_resolveFrom at the canonical chain
(resolveSeqOn = (resolveFrom …).eraseEmpty by rfl),
hasConstantPositiveOrderAlongCenters_eraseEmpty, and the reading map's identity
comap (restrictLE _) (outerTriple).I = T.I.restrictOpens U (IdealSheaf.pullback_comp).
The second half of clause (iv) for the value resolveSeqOn bo T U hU: the last weak transform
of 𝓘|_U is the unit ideal (weakTransformSeq_last_resolveFrom_eq_top at the canonical chain,
through the erasure weakTransformSeq_last_eq_top_eraseEmpty and the reading map's identity).
The centres of resolveSeqOn bo T U hU have simple normal crossings with the accumulated family
totalTransformSeqFrom (restrictTriple T U).F at their stage: clause (3′) of [Kol07, Definition 66]
in the family form, from its ideal-sheaf form isOfOrderGe_zero_resolveSeqOn
(Hironaka/Resolution/Analytic/Wlo09/Monomial.lean) through
hasSncWith_totalTransformSeqFrom_center_of_forall_lt.
Restatements under the names of the clauses #
Clause (ii) of [Hir64, Main Theorem II′(N), p. 156] for the value resolveSeqOn bo T U hU, with
the predicate HasConstantPositiveOrderAlongCenters of
hasConstantPositiveOrderAlongCenters_resolveSeqOn unfolded: at every stage there is a positive
constant equal to the order of the weak transform of 𝓘|_U at every point of the centre. Used by
resolveFamExt_mainTheoremIIpp.
Clause (iii) of [Hir64, Main Theorem II′(N), p. 156] for the value resolveSeqOn bo T U hU: at
every stage the boundary sequence of the restricted boundary ideal sheaf has only normal crossings
with the centre; clause (3′) isOfOrderGe_zero_resolveSeqOn read through
restrictTriple_F_idealSheaf.
The first half of clause (iv) for the value: the last boundary has only normal crossings
(hasOnlyNormalCrossings_boundarySeq_last_of_isOfOrderGe_zero at isOfOrderGe_zero_resolveSeqOn,
through restrictTriple_F_idealSheaf).