ScalingStacks

Remark 4.43 . [02QL]

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Remark 4.43.

When DΨD_{\Psi} is only generated by its global sections, the polytope ΔΨ\Delta_{\Psi} may not determine the variety XΣX_{\Sigma}, but it does determine a polarized toric variety that is the image of XΣX_{\Sigma} by a toric morphism. Write Δ=ΔΨ\Delta=\Delta_{\Psi} for short. Let M⁡(Δ)M(\Delta) be as in Notation 3.103 and choose m∈aff⁡(Δ)∩Mm\in\operatorname{aff}(\Delta)\cap M. Set N⁡(Δ)=M​(Δ)∨N(\Delta)=M(\Delta)^{\vee}. The translated polytope Δ−m\Delta-m has the same dimension as its ambient space LΔ=M​(Δ)ℝL_{\Delta}=M(\Delta)_{\mathbb{R}}. By the theorem above, it defines a complete fan ΣΔ\Sigma_{\Delta} in N​(Δ)ℝN(\Delta)_{\mathbb{R}} together with a support function ΨΔ:N⁡(Δ)→ℝ\Psi_{\Delta}\colon N(\Delta)\to\mathbb{R}. The projection N→N⁡(Δ)N\to N(\Delta) induces a toric morphism

φ:XΣ⟶XΣΔ,\varphi\colon X_{\Sigma}\longrightarrow X_{\Sigma_{\Delta}},

the divisor DΨΔD_{\Psi_{\Delta}} is ample, and DΨ=φ∗​DΨΔ+div⁡(χ−m)D_{\Psi}=\varphi^{*}D_{\Psi_{\Delta}}+\operatorname{div}(\chi^{-m}).

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