The compatibility clause and the end-result embedding of a compatible family #
[Wlo09, Theorem 2.0.3, (4)] for every compatible family: for relatively compact opens U₁ ≤ U₂
the restriction of the succession over U₂ is an extension ([Wlo09, Definition 3.2.6]) of the
succession over U₁. Indeed compat says the value on U₁ is the value on U₂ pulled back
along the open inclusion with the empty blow-ups erased; the restriction is stage-wise isomorphic
to that pull-back (isExtensionOf_restrict_toSuccession_of_pullback), which is an extension of
its cleaned list (isExtensionOf_toSuccession_eraseEmpty). By the second clause of [Kol07, 34.1]
and [Wlo09, Theorem 3.5.1, (2)], the end-result embedding endResultEmbedding is an analytic open
embedding over M onto the preimage of U₁, functorial and the identity on U₁ ≤ U₁, from the
last-stage lemmas isLocalDiffeomorph_pullbackLiftLast, injective_pullbackLiftLast,
stageMap_last_pullbackLiftLast, range_pullbackLiftLast, stageMap_last_eraseEmptyLast,
stageMap_last_stageOfEq and eq_of_stageMap_last_comp_eq.
For a compatible family and relatively
compact opens U₁ ≤ U₂, the restriction to U₁ of the succession over U₂ is an extension of the
succession over U₁: the clause isExtensionOf_restrict of the extension-compatible families, for
every compatible family.
The end-result embedding is a local analytic isomorphism (a composite of the last-stage lift of the open inclusion and two diffeomorphisms).
The embedding of end results is an analytic open embedding (Kollár's open immersion): a local analytic isomorphism, injective as the last-stage lift of the injective open inclusion after two diffeomorphisms.
The end-result embedding is OVER M — the composite blow-down of U₂'s end
result after the embedding is the inclusion U₁ ⊆ U₂ after the composite blow-down of U₁'s end
result (stageMap_last_pullbackLiftLast, stageMap_last_eraseEmptyLast,
stageMap_last_stageOfEq).
The image of the
embedding of end results is the preimage of U₁ under the composite blow-down of U₂'s end result
(range_pullbackLiftLast; the two diffeomorphisms are onto).
The embeddings compose —
emb₂₃ ∘ emb₁₂ = emb₁₃ for U₁ ≤ U₂ ≤ U₃ (uniqueness of maps over M,
eq_of_stageMap_last_comp_eq: both sides are open maps over M).
The embedding of an open into itself is the identity,
emb₁₁ = id (eq_of_stageMap_last_comp_eq against id).