ScalingStacks

Proof. [02VZ]

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Proof.

Let (∥⋅∥v)v∈M𝕂(\|\cdot\|_{v})_{v\in M_{\mathbb{K}}} be a metric on LL and write L¯=(L,(∥⋅∥v)v∈M𝕂){\overline{L}}=(L,(\|\cdot\|_{v})_{v\in M_{\mathbb{K}}}). Suppose first that L¯{\overline{L}} is toric and quasi-algebraic. Let S⊂M𝕂S\subset M_{\mathbb{K}} be a finite set containing the Archimedean places, 𝕂S∘\mathbb{K}^{\circ}_{S} as in Definition 2.51, e≥1e\geq 1 an integer and (𝒳,ℒ)({\mathcal{X}},{\mathcal{L}}) a proper model over 𝕂S∘\mathbb{K}^{\circ}_{S} of (XΣ,L⊗e)(X_{\Sigma},L^{\otimes e}) so that ∥⋅∥v\|\cdot\|_{v} is induced by the localization ℒv{\mathcal{L}}_{v} for all v∉Sv\notin S. Over 𝕂\mathbb{K}, there is an isomorphism from (𝒳,ℒ)({\mathcal{X}},{\mathcal{L}}) to the canonical model (𝒳Σ,ℒe​Ψ)({\mathcal{X}}_{\Sigma},{\mathcal{L}}_{e\Psi}). Since 𝕂S∘\mathbb{K}^{\circ}_{S} is Noetherian, this isomorphism and its inverse are defined over 𝕂S′∘\mathbb{K}^{\circ}_{S^{\prime}} for certain finite subset S′S^{\prime} containing SS. Thus, enlarging the finite set SS if necessary, we can suppose without loss of generality that (𝒳,ℒ)({\mathcal{X}},{\mathcal{L}}) agrees with the canonical model (𝒳Σ,ℒe​Ψ)({\mathcal{X}}_{\Sigma},{\mathcal{L}}_{e\Psi}). Hence, ∥⋅∥v=∥⋅∥v,e​Ψ1/e=∥⋅∥v,Ψ\|\cdot\|_{v}=\|\cdot\|_{v,e\Psi}^{1/e}=\|\cdot\|_{v,\Psi} for all places v∉Sv\notin S. In consequence, it is an adelic toric metric.

Conversely, suppose that L¯{\overline{L}} is a toric adelic metrized line bundle. Let SS be the union of the set of Archimedean places and {v∈M𝕂|ψv≠Ψ}\{v\in M_{\mathbb{K}}|\psi_{v}\neq\Psi\}. By definition, this is a finite set. Let (𝒳Σ,ℒΨ)({\mathcal{X}}_{\Sigma},{\mathcal{L}}_{\Psi}) be the canonical model over 𝕂S∘\mathbb{K}^{\circ}_{S} of (XΣ,L)(X_{\Sigma},L). Then ∥⋅∥v\|\cdot\|_{v} is the metric induced by this model, for all v∉Sv\notin S. Hence L¯{\overline{L}} is quasi-algebraic. ∎

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