Pull-backs of blow-up sequences up to empty blow-ups #
The vocabulary predicate FiniteSuccession.IsPullbackUpToEmptyAlong R S g (Włodarczyk's "the
induced sequence g^*(S) is an extension of R" [Wlo09, Theorem 3.5.1 (2)]) is read off the
pull-back of a blow-up sequence along a local analytic isomorphism (BlowUpSequence.pullback, the
sequence of the fibre products [Wlo09, Proposition 3.4.1]):
BlowUpSequence.isPullbackUpToEmptyAlong_of_isExtensionOf: if the pull-back ofLalongh : U' → Uis an extension ofR([Wlo09, Definition 3.2.6]) andhis the restriction ofg : N → M, thenRis the pull-back ofLalonggup to empty blow-ups. The lift of a stageR_{j_k}toL_kis the stage lift of the pull-back (pullbackLift) after the inverse of the identification of the extension; the clauses come from the stage lifts (stageMap_pullbackLift,map_pullbackLift) and the centres of the pull-back (center_pullback).BlowUpSequence.isPullbackUpToEmptyAlong_eraseEmpty_pullback: the pull-back with its empty blow-ups erased ([Kol07, 32]) is such anR(isExtensionOf_toSuccession_eraseEmpty).CompatibleFamily.isPullbackUpToEmptyAlong_seqOn: for two compatible families whose values onU'and on its imageg(U')are related by the commutation equation of a family functor (AnalyticFamilyFunctor.CommutesWithLocalIsos, Kollár's [Kol07, 34.1] read per open), the value onU'is the pull-back alonggup to empty blow-ups of the value on every relatively compact openU ⊇ g(U'): the compatibility of the family alongg(U') ⊆ U(CompatibleFamily.compat),eraseEmpty_pullback_eraseEmptyandpullback_comp.
An extension of the pull-back is a pull-back up to empty blow-ups: if the pull-back of
the sequence L over U ⊆ M along the local analytic isomorphism h : U' → U is an extension of
R ([Wlo09, Definition 3.2.6]) and h is the restriction of g : N → M, then R is the
pull-back of L along g up to blow-ups with empty centre ([Wlo09, Theorem 3.5.1 (2)]): the lift
of the stage R_{j_k} is the stage lift of the pull-back after the inverse of the identification
of the extension.
The pull-back with its empty blow-ups erased ([Kol07, 32]) is the pull-back up to empty
blow-ups: isPullbackUpToEmptyAlong_of_isExtensionOf at the extension
isExtensionOf_toSuccession_eraseEmpty.
The value on U' is the pull-back along g of the value on any U ⊇ g(U'), up to empty
blow-ups ([Wlo09, Theorem 3.5.1 (2)]), for two compatible families related on U' and its image
g(U') by the commutation equation of [Kol07, 34.1]: the compatibility of the family along
g(U') ⊆ U rewrites the value on g(U') as the erased pull-back of the value on U, the two
erasures and pull-backs combine (eraseEmpty_pullback_eraseEmpty, pullback_comp), and
isPullbackUpToEmptyAlong_eraseEmpty_pullback reads the result.