The cocycle identity of the shrunk gluing data #
The K-gluing core of the shrunk pieces (Hironaka.AnalyticSpace.Glue.Assemble) satisfies the
cocycle identity tRes i j k ≫ tRes j k i ≫ tRes k i j = 𝟙 on the triple pieces
Z_ijk = (Y_i | A_i) | (W_ij ⊓ W_ik) (Shrunk.cocycle), hence is K-gluing data (Shrunk.data,
Hironaka.AnalyticSpace.Glue.Data) and glues to a K-space (Hironaka.AnalyticSpace.Glue.KSpace).
The identity is a morphism identity, not a pointwise one: the points of Z_ijk lie in the cocycle
neighbourhoods N_ijk and N_iki (Hironaka.AnalyticSpace.Glue.TripleSet, through the shrinking
constraints), on which the transitions satisfy φ_jk ∘ φ_ij = φ_ik and φ_ki ∘ φ_ik = φ_ii = id as
morphisms (cocycleNhd_eq, the cocycle on a neighbourhood of the real points, as in the proof of
[Car57, §3, Proposition 2]); the three restricted transitions, pushed into the ambient
complexifications, are these composites restricted along the inclusion of Z_ijk (uniqueness of
lifts along open immersions).
Conventions. inclZTo Ω is the inclusion of Z_ijk into Y_i | Ω for an open subset Ω ⊆ Y_i
containing its points; every morphism of the argument out of Z_ijk into a restriction of Y_i is
identified with such an inclusion by eq_inclZTo (uniqueness of lifts), and the chains of
inclusions collapse by inclZTo_comp_restrictOpenIncl. Repeated indices need no case split:
W_ii = ⊤ and P i i = refl, so φ_ii = id (e_P_diag_comp_ofRestrict), and t_comp_incl₂'
covers the diagonal transition; for an empty W_ij ⊓ W_ik the identity holds on the empty space by
the same argument.
The inclusion of a smaller open of a restriction, followed by the double-restriction inclusion, is the double-restriction inclusion of the smaller open.
The inclusion of a smaller open of a restriction, followed by the double-restriction inclusion, is the double-restriction inclusion of the smaller open.
On the diagonal the transition is the identity of Y_i: e_ii ≫ ofRestrict = ofRestrict.
Points of the triple pieces lie in the cocycle neighbourhoods #
A point of A_i ∩ W_ij ∩ W_ik lies in the cocycle neighbourhood N_ijk: the triple
constraint of the shrinking.
The inclusions of the triple pieces #
The inclusion of the triple piece Z_ijk = (Y_i | A_i) | (W_ij ⊓ W_ik) into Y_i | Ω, for an
open Ω containing its points.
Equations
- S.inclZTo i j k Ω h = AnalyticSpace.Glue.liftAlong ((D.C i).Y.ofRestrict Ω) (AnalyticSpace.Glue.incl₂ (D.C i).Y.toKLocallyRingedSpace (S.A i) (S.W i j ⊓ S.W i k)) ⋯
Instances For
Uniqueness of lifts: a morphism of Z_ijk into Y_i | Ω over the inclusion of Z_ijk into
Y_i is the inclusion.
The restricted transitions, pushed into the ambient complexifications #
The transition followed by the inclusion into Y_j, on the diagonal included.
The restricted transition tRes i j k, pushed into Y_j, is φ_ij on the points of Z_ijk.
The restricted transition tRes i j k, pushed into Y_j, is φ_ij on the points of Z_ijk.
The first restricted transition, pushed into Y_j | Ω_jk: the first factor of the composite
transition compTrans restricted to Z_ijk ⊆ N_ijk.
The first restricted transition, pushed into Y_j | Ω_jk: the first factor of the composite
transition compTrans restricted to Z_ijk ⊆ N_ijk.
The first two restricted transitions, pushed into Y_k | Ω_ki: by the cocycle on N_ijk
they are φ_ik on the points of Z_ijk, the first factor of compTrans for the triple
(i, k, i) restricted to Z_ijk ⊆ N_iki.
The first two restricted transitions, pushed into Y_k | Ω_ki: by the cocycle on N_ijk
they are φ_ik on the points of Z_ijk, the first factor of compTrans for the triple
(i, k, i) restricted to Z_ijk ⊆ N_iki.
The cocycle identity and the gluing data #
The cocycle identity of the shrunk gluing core: by the cocycles on N_ijk and N_iki the
composite of the three restricted transitions, pushed into Y_i, is φ_ii = id on the points of
Z_ijk, hence the inclusion of Z_ijk.