The pull-back of a list of centres, stage by stage #
For a list of centres L on M and a local analytic isomorphism h : N → M,
BlowUpSequence.pullback is the list of the preimage centres under the successive lifts
h_i : N_i → M_i (pullbackLiftAux), the pull-back of a blow-up sequence along a smooth
morphism [Kol07, Definition 30, 30.1]. This file records, by induction on the list, what the
succession of h^* L carries at each stage in terms of L's data pulled back along the lifts:
- the lifts are local analytic isomorphisms, surjective when
his (isLocalDiffeomorph_pullbackLiftAux,surjective_pullbackLiftAux); - the centres (
center_pullbackAux), the weak transforms (weakTransformSeqAux_pullback), the boundaries (boundarySeqAux_pullback, along a surjectiveh: Hironaka's reduced transform is natural along surjective local isomorphisms,reducedTransform_comap_liftStep) and, along a sequence of order≥ mfor(I, m), the marked transforms (markedTransformSeqAux_pullback, the marking being legitimate at every stage), each thecomapalong the lift of the datum onL; - the descent of [Kol07, Definition 66] (
isOfOrderGe_of_pullback): ifh^* Lis a smooth blow-up sequence of order≥ mfor(h^* I, m, h^* E)[Kol07, Definition 66] andhis surjective, thenLis one for(I, m, E): stage by stage, the normal-crossings clause and the order clause come back along the bijective germ maps (Hironaka.Resolution.Analytic.Functor.PullbackTransport), the marking of the first transform being legitimate once the order clause at stage0is known.
This is how the clauses of the descended functor are read on the pull-back to the cover in the global case of the proof of [Kol07, Theorem 103] (the functoriality package is local, as the proof remarks at the end of its local case).
The lifts #
The lifts of a local analytic isomorphism to the stages are local analytic isomorphisms.
The lifts of a surjective local analytic isomorphism to the stages are surjective
(surjective_liftStep at each step).
The lift h_i : N_i → M_i of a
local analytic isomorphism to the stage i is a local analytic isomorphism.
The lifts of a surjective local analytic isomorphism are surjective.
The stages of the pull-back #
The centres of h^* L are the pull-backs of the centres of L along the lifts.
The weak transforms along h^* L are the pull-backs of the weak transforms along L
(weakTransform_comap_liftStep at each step).
The boundaries along h^* L, for a SURJECTIVE h, are the pull-backs of the boundaries along
L (reducedTransform_comap_liftStep at each step).
Along a sequence of order ≥ m for (I, m, E₀), the marked transforms along h^* L are the
pull-backs of the marked transforms along L (birationalTransform_comap_liftStep at each step;
the marking is legitimate by the order clause of [Kol07, Definition 66] at that step).
The stages of the pull-back, indexed by Fin, along the lifts pullbackLift #
The centres of h^* L along the lifts (Fin-indexed form of center_pullbackAux).
The weak transforms along h^* L along the lifts (Fin-indexed form of
weakTransformSeqAux_pullback).
The boundaries along h^* L, for a surjective h, along the lifts (Fin-indexed form of
boundarySeqAux_pullback).
The marked transforms along h^* L, for L of order ≥ m for (I, m, E₀), along the lifts
(Fin-indexed form of markedTransformSeqAux_pullback).
The descent of [Kol07, Definition 66] #
[Kol07, Definition 66] descends along a surjective local analytic isomorphism: if h^* L
is a smooth blow-up sequence of order ≥ m for (h^* I, m, h^* E₀) and h is surjective, then
L is one for (I, m, E₀). Stage by stage: the normal-crossings clause and the order clause at
the first centre come back along the bijective germ maps
(HasOnlyNormalCrossingsWith.of_comap_of_surjective,
ordAlongIdeal_comap_of_isLocalDiffeomorphAt, every point of the centre having a preimage), and
the tail of h^* L is the pull-back of the tail of L along the surjective lift, for the first
marked transform and the first boundary (birationalTransform_comap_liftStep — the marking being
legitimate by the order clause just obtained — and reducedTransform_comap_liftStep).
Transfer of the clauses along an equality of lists #
The output clause of [Kol07, Theorem 103, (1)] transfers along an equality of lists (the points
of the last stage are transported by subst).
The output clause at the last stage, read at any index k provably equal to the length.