ScalingStacks

2.1 . [0382]

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2.1.

A model of XX is given by a proper flat scheme 𝒳{{\mathscr{X}}} over S:=Spec​K∘S:={\rm Spec}\,K^{\circ} together with an isomorphism hh between XX and the generic fiber 𝒳η{{\mathscr{X}}}_{\eta} of the SS-scheme 𝒳{{\mathscr{X}}} which we read as an identification. Given a model 𝒳{{\mathscr{X}}} of XX there is a canonical surjective reduction map red:XanβŸΆπ’³s{\mathrm{red}}\colon X^{\mathrm{an}}\longrightarrow{{\mathscr{X}}}_{s} where 𝒳s{{\mathscr{X}}}_{s} denotes the special fiber π’³βŠ—K∘K~{{\mathscr{X}}}\otimes_{K^{\circ}}\tilde{K} of 𝒳{{\mathscr{X}}} over SS.

Let LL be a line bundle on the proper variety XX. A model of (X,L)(X,L) or briefly a model of LL is given by a model (𝒳,h)({{\mathscr{X}}},h) of XX together with a line bundle β„’{\mathscr{L}} on 𝒳{{\mathscr{X}}} and an isomorphism hβ€²h^{\prime} between LL and hβˆ—β€‹(β„’|𝒳η)h^{*}({\mathscr{L}}|_{\mathscr{X}_{\eta}}) which we read as an identification.

Given a model (𝒳,β„’)({{\mathscr{X}}},{\mathscr{L}}) of (X,LβŠ—m)(X,L^{\otimes m}) for some mβˆˆβ„•>0m\in\mathbb{N}_{>0} there is a unique metric βˆ₯βˆ₯β„’{\|\ \|}_{\mathscr{L}} on LanL^{\mathrm{an}} over XanX^{\mathrm{an}} which satisfies the following: Given an open subset 𝒰{\mathscr{U}} of 𝒳{{\mathscr{X}}}, a frame tt of β„’{\mathscr{L}} over 𝒰{\mathscr{U}}, and a section ss of LL over U=Xβˆ©π’°U=X\cap{\mathscr{U}} we write sβŠ—m=h​ts^{\otimes m}=ht for some regular function hh on UU and get β€–sβ€–=|h|m\|s\|=\sqrt[m]{|h|} on Uan∩redβˆ’1​(𝒰s)U^{\mathrm{an}}\cap{\mathrm{red}}^{-1}({\mathscr{U}}_{s}). Such a metric on LanL^{\mathrm{an}} is called a model metric determined on 𝒳{{\mathscr{X}}}.

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