The push-forward of a list of centres is the push-forward of its succession #
The push-forward of a blow-up sequence of a closed submanifold S ⊆ M to M
[Kol07, Definition 30, 30.3] exists in two forms: FiniteSuccession.pushforward on finite
successions, recursing on the stage index from the start (M, S, e_0 = id), and
BlowUpSequence.pushforward on lists of centres, recursing on the list from any PushforwardStage.
The commutation of the order-reduction functor with closed embeddings ([Kol07, 34.3];
[Kol07, Theorem 103, (3)]) is stated on the former, the push-forward being the correspondence of
[Kol07, Corollary 85], while a blow-up sequence functor's value is a list. This file
identifies the two:
FiniteSuccession.ext_of: two successions with equal lengths and stages and heterogeneously equal centres and maps are equal;PushforwardStage.pushforwardOfStage P T: the succession recursion from an arbitrary start stageP(FiniteSuccession.pushforward_eq_pushforwardOfStageis the identification at the canonical start), and the peeling lemmapushforwardOfStage_cons: oncons hZ Rwith a nonempty centreZ, the push-forward starts with(j_0)_* Zand continues from the next stage; the chosen codimension of the first blow-up of the succession, a classical choice fromisMonoidal, equals the codimensioncofhZbyIsClosedSubmanifold.codim_eq_of_nonempty;BlowUpSequence.toSuccession_pushforward: for a listLwith no empty centre (the output convention of every blow-up sequence functor, [Kol07, 32]),(L.pushforward hS).toSuccession = L.toSuccession.pushforward hS. The hypothesis is needed: for an empty centre every codimension is legitimate (isClosedSubmanifold_empty'), the chosen codimension of the succession is free, and the two push-forwards may blow upMalong "the empty set of codimensionc'" for differentc'.
The identification is used where a functor's value, a list, is compared with the push-forward of a succession, in the descent of the order-reduction functors to a hypersurface of maximal contact.
Extensionality of finite successions: two successions of the same
length whose stages agree and whose centres and blow-downs are heterogeneously equal are equal
(isMonoidal is a proof).
The centre Z_i of a succession on a manifold modelled on 𝕜^{n-s}, as a closed submanifold
for the identity chart (pushforwardCenterSub from any base).
The blow-down T_{i+1} → T_i as a blowing-up for the identity chart (pushforwardIsBlowUp
from any base).
The recursion from an arbitrary start stage #
The stages of the push-forward of T started at P (pushforwardAux with P in
place of (M, S, id)).
Instances For
The later stages of the push-forward started at P.
Instances For
The centre of the push-forward at step i, as a closed submanifold.
The centre of the push-forward at step i: the ideal sheaf of Z_i^X.
Equations
- P.centerOf T i hi = ⋯.idealSheaf
Instances For
The blow-down of the push-forward at step i.
Equations
- P.mapOf T i hi = Manifold.blowUpπ ψ ⋯
Instances For
The centres, typed on finStages.
Instances For
The blow-downs, typed on finStages.
Instances For
Each blow-down is the monoidal transformation with centre the ideal sheaf of Z_i^X.
[Kol07, Definition 30, 30.3] from an arbitrary start stage P: the push-forward of the
succession T on T₀ to P.space (FiniteSuccession.pushforward is the instance at
the canonical start, FiniteSuccession.pushforward_eq_pushforwardOfStage).
Equations
Instances For
Congruences #
blowUpStep depends on the centre and its codimension only up to propositional equality.
The pushed-forward centre depends on the centre and its codimension only up to propositional equality.
The blow-down along the pushed-forward centre, up to propositional equality of the centre and its codimension.
The pushed-forward centre, along an equality of stages.
The blow-down along the pushed-forward centre, along an equality of stages.
The push-forward of nil and of cons #
The push-forward of the empty succession is the empty succession on P.space.
The support of the first centre of cons hZ R is Z.
[Kol07, 32] removing the obstruction: for a nonempty first centre, the succession's chosen
codimension of the first blow-up of cons hZ R is the codimension c of hZ
(IsClosedSubmanifold.codim_eq_of_nonempty, across the chosen chart and the identity chart).
The stages of the push-forward of cons hZ R after the first are those of the push-forward
of R started at the first blow-up step (the peeling of the recursion; the first step's data are
identified through codim_cons_zero).
The blow-downs of the push-forward of cons hZ R after the first are those of the push-forward
of R started at the first blow-up step (typed on the stages, stageAux_cons_succ).
The peeling lemma: for a nonempty first centre Z, the push-forward of cons hZ R started
at P is cons of the pushed-forward centre (j_0)_* Z and the push-forward of R started at the
first blow-up step.
The stages are the general recursion's at the canonical start (M, S, id).
The push-forward is the general recursion's at the canonical start (M, S, id).
The list push-forward from any start stage, as a succession, is the general succession push-forward of the list's succession — for a list with no empty centre.
The push-forward of lists agrees with the push-forward of successions:
for a closed submanifold hS : IsClosedSubmanifold ψ S s and a list of centres L on the bundled
S with no empty centre ([Kol07, 32]), the succession of the list push-forward is
the push-forward of the list's succession. The hypothesis is load-bearing: at an empty
centre the chosen codimension is free (isClosedSubmanifold_empty'), and the two
push-forwards need not agree.