ScalingStacks

2.2 . [03AR]

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2.2.

Let VV be a paracompact strictly KK-analytic space. We use here the analytic spaces and the terminology introduced by Berkovich in [Ber93, Section 1]. Then a formal K∘{K^{\circ}}-model is an admissible formal scheme 𝔙{\mathfrak{V}} over K∘{K^{\circ}} [Bos14, Β§7.4] with a fixed isomorphism 𝔙η≅V{\mathfrak{V}}_{\eta}\cong V on the generic fiber 𝔙η{\mathfrak{V}}_{\eta} which we again use for identification. Note that we have a canonical reduction map Ο€:V→𝔙s\pi:V\to{\mathfrak{V}}_{s} to the special fiber 𝔙s{\mathfrak{V}}_{s} (see [GRW15, Section 2]). If ΞΆY\zeta_{Y} is the generic point of an irreducible component YY of 𝔙s{\mathfrak{V}}_{s}, then xYβ‰”Ο€βˆ’1​(ΞΆY)x_{Y}\coloneqq\pi^{-1}(\zeta_{Y}) is finite and the points in this preimage are called divisorial points of VV.

The category of paracompact strictly KK-analytic spaces is equivalent to the category of quasiseparated rigid analytic varieties over KK with a strictly KK-affinoid G{\rm G}-covering of finite type (see [Ber93, Β§1.6]) and hence we may apply Raynaud’s theorem from [Bos14, Theorem 8.4.4]. In particular, we see that a formal K∘{K^{\circ}}-model of VV exists and that the set of isomorphism classes of formal K∘{K^{\circ}}-models is again directed. Some of the references in the following require that VV is compact, because the original formulation of Raynaud’s theorem in [BL93a, Theorem 4.1] used that the underlying rigid space is quasicompact and quasiseparated. This will be bypassed by using the more general version in [Bos14, Theorem 8.4.4] for paracompact VV (remember that paracompact includes Hausdorff).

Let LL be a line bundle on VV which means that LL is a locally free sheaf of rank 11 on the G{\rm G}-topology. We always consider the G{\rm G}-topology induced by the strictly KK-affinoid domains in VV. A formal K∘{K^{\circ}}-model (𝔙,𝔏)({\mathfrak{V}},{\mathfrak{L}}) of (V,L)(V,L) consists of a formal K∘{K^{\circ}}-model 𝔙{\mathfrak{V}} of VV and a line bundle 𝔏{\mathfrak{L}} on 𝔙{\mathfrak{V}} with a fixed isomorphism from 𝔏|V{\mathfrak{L}}|_{V} to LL which we use for identification. The argument in [Gub98, Lemma 7.6] shows that (V,L)(V,L) always has a formal K∘{K^{\circ}}-model.

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