Non-singularity and properness of a glued space over a base #
Two clauses of the resolution theorem for analytic spaces (the manifold clause (1) and the
properness clause (3) of the resolution problem, [Hir64, Introduction, p. 111]; Kol07, Theorem 45,
(1); [Wlo09, §4]: "des_V : Ṽ → V is bimeromorphic and proper") for a gluing datum
G : GlueOver X R π dom:
isNonsingular_gluedOver: a glued space of non-singular pieces is non-singular: every point comes from a piece through the open immersionιGlued i(exists_ιGlued_eq), and an open immersion preserves the regularity of the stalk (mem_reg_iff_of_isOpenImmersion);isProperMap_descMap_of_iUnion: the descended map is proper when the base open subsets coverXand every piece map is proper onto its base open subset: properness is local on the target (isProperMap_of_restrictPreimage_cover), and overdom ithe descended map is thei-th piece map (isProperMap_restrictPreimage_descMap,Hironaka.AnalyticSpace.Glue.OverProper).
Both are applied to the glued local resolutions in
Hironaka.Resolution.Analytic.Kol07Thm45.ResolutionClauses.
A glued space of non-singular pieces is non-singular (the smoothness clause Kol07, Theorem
45, (1), piece by piece): every point of the glued space is the image of a point of a piece under
the open immersion ιGlued i, and regularity of the stalk is carried across an open immersion
(mem_reg_iff_of_isOpenImmersion).
The descended map is proper when the base open subsets cover X and every piece map is proper
onto its base open subset ("des_V is proper", [Wlo09, §4]; the properness clause of the
resolution problem, [Hir64, Introduction, p. 111]): properness is local on the target
(isProperMap_of_restrictPreimage_cover), and over dom i the descended map is the i-th piece
map (isProperMap_restrictPreimage_descMap).