The parts of a piece's local resolution over a base open, read on the ambient #
Two bookkeeping identities for the assembly of the mixed-pair transition of the common datum
(CoproductMixedTransition.lean):
- a point of a piece's local resolution lies over the base open
domOpens Q(inX) iff its ambient point — the last stage's composite blow-down read through the closed inclusion — lies in the ambient openQ(toFun_toSpaceMap_eq,pieceOverIncl_mem_domOpens_iff,localResolutionMap_comp_ι); - along the open immersion
localResolutionHomOn(LocalResolutionOn.lean) of the piece's local resolution overW'into the local resolution of(T, W)along an open embeddinggof admissible inputs, the part of the source over the base opendomOpens Q(Q ≤ W') maps ONTO the part of the target over the ambient openg(Q)(range_toFun_localResolutionHomOn,stageMap_last_liftOn).
Both are used by isoOfRangeEq in the assembly: the two padded pieces' parts over one base open
P are identified with the local resolution of the common admissible input over W₁' through the
common run's local resolution. hbed is the only hypothesis. Not in the sources; bookkeeping.
A point of the local resolution lies over the base open of Q iff its ambient point lies in
Q — toSpaceMap = pieceOverIncl ∘ Π
(toFun_toSpaceMap_eq), pieceOverIncl_mem_domOpens_iff, and the square
ι_W ∘ Π = composite ∘ ι_Y (localResolutionMap_comp_ι).
The part of the piece's local resolution over the base open domOpens Q maps under
localResolutionHomOn ONTO the part of the target's local resolution over the ambient open g(Q)
(Q ≤ W'): the lift covers g
(stageMap_last_liftOn), the range of the immersion is the part over g(W')
(range_toFun_localResolutionHomOn), and g is injective.