The compatibility of the piece traces along the gluing #
Kollár's agreement of the centres on the overlaps, (37.2) in [Kol07, Proposition 37, proof]. The
coproduct member of a label is traced on every piece (pieceTrace), and gluedMembersOn
(CoproductGluedFamily.lean) glues the traces into a family on the glued local resolution once
they are compatible along the transitions with the identity labelling (LabelledCompat).
Compatibility of a pair of pieces is a POINTWISE matter
(compatClosedSubspaces_pair_of_forall_exists_isoOver,
Hironaka/Resolution/Analytic/Kol07Thm45/Glue/OverRigidity.lean): at each point of the gluing open
an isomorphism over X of the parts over a neighbourhood carrying the one trace to the other, with
the rigidity of the piece map over that neighbourhood (rigidOver_pieceToSpace, the only use of
hind).
exists_isoOver_pieces_of_sum(the conjugation lemma): at a point of the domains of a piece ofD₁and a piece ofD₂, the mixed-pair transition of the doubled datumsumPadData D₁ D₂— an isomorphism overXbetween the parts overPof the two PADDED pieces' local resolutions carrying the doubled run's member of every label — conjugated by the piece isomorphisms of the padding identities (restricted overP,Hom.restrictTo) is an isomorphism overXbetween the parts overPof the two UNPADDED pieces' local resolutions carrying, for every labelσof the doubled run, the⊤-extended tracesumLabelTraceofD₂on the second piece to that ofD₁on the first (comap_resIn_sumPadData_inl/_inr, the label embeddings' clauses, the padding identity's member clause and squares).labelledCompat_pieceTrace: the piece traces are compatible with the identity labelling — at the diagonal pair(D, D)with the padded reading openspadReadingOpens, the padding identities frompadIdentityOnread at the reading opens of the gluing (exists_padIdentity_of_padPreimageOpens_eq), the two label embeddings, the conjugation lemma at a point of the gluing open, and the label coherencelabel_route_eq_of_ne_top(DoubledDatumLabels.lean) to read the doubled run's labellab₁ (o₁.symm l)as the labellon both pieces; a label whose member is the unit ideal has all its traces equal to the unit ideal and needs no coherence.
Not in the sources beyond Kollár's proof; bookkeeping.
The mixed-pair transition of the doubled datum, conjugated by the padding identities of the
two pieces ((37.2) in [Kol07, Proposition 37, proof]) — at a point x of the domains of the
piece i of D₁ and the piece j of D₂ (read at the reading opens V₁, V₂ carried by the
padded ones W₁, W₂: hpre₁, hpre₂), an open P ∋ x inside both domains and an isomorphism
over X between the parts over P of the two pieces' local resolutions carrying, for every label
σ of the doubled run, the ⊤-extended trace of D₂ on the piece j to that of D₁ on the
piece i. The binders are the conjuncts of exists_padIdentity_of_padPreimageOpens_eq for the
two padded copies (o, ψ with the member clause hmem, and per piece an isomorphism over the
piece with the square resIn⁺ i ≫ ψ = ψᵢ ≫ resIn i) and the two label embeddings with their
clauses.
The piece traces of the coproduct members are compatible along the gluing with the identity
labelling ((37.2) in [Kol07, Proposition 37, proof]) — the hypothesis hc of gluedMembersOn
and exists_gluedMembers_resolutionOn (CoproductGluedFamily.lean). hind enters only through
the rigidity of the piece maps (rigidOver_pieceToSpace).