Functoriality of localResolutionHomOn along a composite #
The sequence functor commutes with open embeddings, whose pull-back lifts them stage by stage
([Kol07, Definition 30.1]; [Kol07, 34.1]); the lift is unique in the library's sense — a
continuous map over the embedding that pulls dense opens back to dense sets is the lift
(eq_of_stageMap_last_comp_eq, OrderReduction/LiftUnique.lean; not in the sources). Applied to
a COMPOSITE g ∘ k of two open embeddings of admissible inputs this gives the functoriality of
the lift and the open immersion of LocalResolutionOn.lean:
BEDanFamStar.liftOn_comp:liftOn (g ∘ k) = liftOn g ∘ liftOn kon the last stages — both are continuous lifts ofg ∘ kpulling dense opens back to dense sets (isLocalDiffeomorph_liftOn), and they agree after the last blow-down (stageMap_last_liftOn'three times);BEDanFamStar.localResolutionHomOn_comp:localResolutionHomOn g ∘ localResolutionHomOn k = localResolutionHomOn (g ∘ k)(≫) —homOfPullbackEq_comp_of_comp_eq(ShearOverX.lean) atliftOn_comp;- the congruences
liftOn_congr,localResolutionHomOn_congrin the embedding (the first has no user and is stated for the symmetry with the second); - the INSTANCES
LocalEmbeddingData.resIn_sumPadData_inl/_inr: for the common padded datumS = sumPadData D₁ D₂,S.resIn (inl i) = sumInlResIn ∘ D₁⁺.resIn i(andinr) — the compositessumPadInlAmbient ∘ sigmaMk i = sigmaMk (inl i)andsumInrAmbient ∘ sigmaMk j = sigmaMk (inr j)(sumPadInlAmbient_comp_sigmaMk,sumInrAmbient_comp_sigmaMk). Both instances are equations of morphisms of analytic spaces (≫) with the piece spelled once, as the sum's; the identities to use arecomap_resIn_sumPadData_inl/_inr, where the two spellings of the piece meet as ideal sheaves.
These identities let the members of the common run pulled back along S.resIn (inl i) be read
through sumInlResIn and then through the padded piece's resIn i, which the comparison of two
adjacent levels (CoproductLevelPair.lean) and the compatibility of the piece traces
(CoproductGluedFamilyCompat.lean) need. Not in the sources beyond the pull-back of blow-up
sequences; bookkeeping.
The lift depends on the embedding only through its value — congruence in g (the proofs are
irrelevant).
The open immersion depends on the embedding only through its value — congruence in g.
The lift of a composite of open embeddings is the composite of the lifts
([Kol07, Definition 30.1]) — both are continuous maps of the last
stages over g ∘ k that pull dense opens back to dense sets (local analytic isomorphisms,
isLocalDiffeomorph_liftOn), and they agree after the last blow-down (stageMap_last_liftOn'),
so the uniqueness of the lift (eq_of_stageMap_last_comp_eq) identifies them.
Functoriality of the open immersion of local resolutions along a composite of open
embeddings ([Kol07, Definition 30.1]) — localResolutionHomOn at g ∘ k is the composite of the
two; homOfPullbackEq_comp_of_comp_eq at liftOn_comp.
The common datum's open immersion at an inl piece factors through the first padded
level's ([Kol07, Definition 30.1]; [Kol07, 34.1]) —
S.resIn (inl i) = sumInlResIn ∘ (D₁⁺.resIn i read at the sum's piece), the functoriality
localResolutionHomOn_comp along sigmaMk (inl i) = sumPadInlAmbient ∘ sigmaMk i
(sumPadInlAmbient_comp_sigmaMk, the datum's specific inl inclusion). The second factor is
D₁⁺.resIn i with the piece spelled as the sum's ((sumPadData D₁ D₂).embedding (Sum.inl i),
sumPadOpens … (Sum.inl i)): the statement keeps ONE spelling of the piece, and the identity to
use is comap_resIn_sumPadData_inl, where the two spellings meet as ideal sheaves.
The common datum's open immersion at an inr piece factors through the second padded
level's — S.resIn (inr j) = sumInrResIn ∘ (D₂⁺.resIn j read at the sum's piece)
(sumInrAmbient_comp_sigmaMk); the spelling as for inl.
The pull-back form at inl — pulling a closed subspace of the common run's local
resolution back along S.resIn (inl i) is pulling it back along sumInlResIn and then along
D₁⁺.resIn i (resIn_sumPadData_inl, QuotientSpace.comap_comp; the two spellings of the piece
meet here, as ideal sheaves, where they are definitionally equal at once).
The pull-back form at inr — pulling back along S.resIn (inr j) is pulling back along
sumInrResIn and then along D₂⁺.resIn j.