The fixed-run device with synchronised members #
Kollár's descent of the centres from the disjoint union of a cover: the centre of the disjoint
union agrees on the overlaps, (37.2) in [Kol07, Proposition 37, proof], because the functor
commutes with smooth surjections [Kol07, 34.1]. Two local analytic isomorphisms u v : N → M with
the SAME pulled-back triple (T.pullback u = T.pullback v — the shear's ideal identity hI in the
application) pull the functor's run over a reading open V ⊆ M back to the SAME list over any
relatively compact open W' ⊆ N whose two images lie in V: this is
seqOn_pullback_eq_of_pullback_eq (ExceptionalFamilyGlue.lean) on the coproduct P := N ⊔ M
with the maps id ⊔ u, id ⊔ v (surjective, so both erasures are no-ops) at the reading open
U' := W' ⊔ V of P, READ ON THE N-SUMMAND (the restricted summand inclusion N|W' → P|U',
pullback_comp). With the synchronisation of RunFamilyRestrict.lean it follows that, when u,
v are moreover open embeddings of one admissible input T', the two open immersions
localResolutionHomOn of local resolutions pull every member of the run's boundary family back to
the SAME closed subspace — the stage-σ member on one side IS the stage-σ member on the other,
no label chosen (the label is a stage of the one run).
The user is the transition between a padded piece and a piece of the other embedding in the common
datum sumPadData D₁ D₂ (CoproductSumData.lean, CoproductMixedTransition.lean):
u := sigmaMk (inl i) ∘ …, v := sigmaMk (inr j) ∘ … ∘ g with the shear g of
exists_padded_equivalence_hom_point. hbed is the only hypothesis. Not in the sources beyond
Kollár's descent; bookkeeping.
The reading open W' ⊔ V of the coproduct N ⊔ M — the union of the two summand
images.
Equations
- Hironaka.Manifold.sumOpens W' V = { carrier := ⇑Hironaka.Manifold.sumInl '' ↑W' ∪ ⇑(Manifold.sigmaMk (Hironaka.Manifold.sumFamily N M) { down := false }) '' ↑V, is_open' := ⋯ }
Instances For
The first summand's image lies in the coproduct's reading open sumOpens.
Relatively compact summands give a relatively compact reading open of the coproduct.
id ⊔ w maps W' ⊔ V into V when w(W') ⊆ V.
id ⊔ w maps W' ⊔ V ONTO V (the M-summand).
The fixed-run device read on a summand ((37.1)–(37.2) in [Kol07, Proposition 37, proof];
[Kol07, 34.1]) — two local analytic isomorphisms u v : N → M with the SAME pulled-back triple
pull the run over V back to the SAME list over any relatively compact W' ⊆ N with u(W') ⊆ V,
v(W') ⊆ V: seqOn_pullback_eq_of_pullback_eq on N ⊔ M with the surjective maps id ⊔ u,
id ⊔ v at the reading open W' ⊔ V, then the restricted summand inclusion
N|W' → (N ⊔ M)|W' ⊔ V (pullback_comp).
The fixed-run device with synchronised members ((37.2) in [Kol07, Proposition 37, proof])
— two open embeddings u, v of ONE admissible input (T', W') into (T, V) pull every member of
the run on T back along the two open immersions of local resolutions to the SAME closed subspace:
the two pulled-back triples coincide (ext'), hence the two pulled-back runs (the device above),
hence the members (comap_localResolutionHomOn_runMembers_eq_of_pullback_eq,
RunFamilyRestrict.lean).