Rigidity of the local resolutions over X #
Kollár's descent of the centres from the disjoint union of an affine cover — the pieces of the
centre agree on the overlaps, (37.2) in [Kol07, Proposition 37, proof] — and the uniqueness of the
canonical isomorphisms of the local resolutions [Kol07, Theorem 36, proof]; Włodarczyk's
transitions over the overlaps [Wlo09, §4, (3)⇒(4)]. The independence of the local resolution from
the embedding, taken as the hypothesis hind : LocalResolutionIndependentOn X bed, says the
isomorphism over the base between two local resolutions is UNIQUE. Read at one local resolution
against itself, this is RIGIDITY: every automorphism over X of a part of a local resolution over
a base open is the identity — the haut hypothesis of isoOver_unique_of_aut (LocalModel.lean),
named RigidOver. This module supplies it for the FOUR maps to X that the resolutions carry,
each by hind's uniqueness applied to the given automorphism AND to 𝟙:
PieceEmbedding.rigidOver_toSpaceMap: the parts of a piece's local resolution over ANY open under its base open (toSpaceMap), by the cover argument oftransition_uniqueat one embedding —exists_localTransition_pair E Eat each point, thenhom_ext_of_cover; with the corollaryrigidOver_toSpaceMap_domOpensatO := E.domOpens Q,Q ≤ W(domOpens_mono);LocalEmbeddingData.rigidOver_pieceToSpace: the pieces of a gluing datum (pieceToSpace) —transition_uniqueati = j;LocalEmbeddingData.rigidOver_resolutionOnToSpace: the gluedresolutionOn(resolutionOnToSpace) — the uniqueness clause ofexists_isoOver_resolutionOn D D;BEDanFamStar.ExhaustionGluing.rigidOver_descMap: the exhaustion glue (descMap) —ExhaustionGluing.isoOver_eq_id(LocalModel.lean), repackaged.
The datum-level and resolutionOn-level forms are the rigidity hypotheses of the gluing of the
exceptional families (compatClosedSubspaces_pair_of_forall_exists_isoOver,
eq_tOver_of_isoOver; CoproductGluedFamilyCompat.lean, ExhaustionChainFamilies.lean); the
piece-level and exhaustion-glue forms are stated for completeness and have no user in the
library. Not in the sources beyond the remarks cited; bookkeeping.
The parts of a piece's local resolution are rigid over X ([Kol07, Theorem 36, proof];
[Wlo09, §4, (3)⇒(4)]; with the independence as hind) — every automorphism over X of the part
over an open O under the base open is the identity. The argument of transition_unique at ONE
embedding: at every point of O the unique local transition
of E with itself (exists_localTransition_pair) is what BOTH t and 𝟙 restrict to
(restrictOver, isIso_restrictOver, restrictOver_over), and morphisms agreeing on a cover agree
(hom_ext_of_cover, comp_eq_of_restrict_eq, restrictOver_comp_restrictIncl).
The named form — rigidity over the base open domOpens Q of an ambient open Q ≤ W.
The parts of a datum's pieces are rigid over X (with the independence as hind) —
transition_unique at i = j, for the automorphism and for 𝟙.
The parts of the glued resolutionOn are rigid over X (with the independence as hind)
— the uniqueness clause of exists_isoOver_resolutionOn D D, for the automorphism and for 𝟙.
The parts of the exhaustion glue are rigid over X — ExhaustionGluing.isoOver_eq_id
(LocalModel.lean), in the RigidOver spelling.