ScalingStacks

Proposition 4.37 . [02QF]

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Proposition 4.37.

Let DΨiD_{\Psi_{i}}, i=1,…,ni=1,\dots,n, be 𝕋\mathbb{T}-Cartier divisors on XΣX_{\Sigma} generated by their global sections. Then

(4.38) (DΨ1⋅⋯⋅DΨn)=MVM⁡(ΔΨ1,…,ΔΨn).(D_{\Psi_{1}}\cdot\dots\cdot D_{\Psi_{n}})=\operatorname{MV}_{M}(\Delta_{\Psi_{1}},\dots,\Delta_{\Psi_{n}}).

where MVM\operatorname{MV}_{M} denotes the mixed volume function associated to the Haar measure volM\operatorname{vol}_{M} on MℝM_{\mathbb{R}} (Definition 3.109). In particular, for a 𝕋\mathbb{T}-Cartier divisor DΨD_{\Psi} generated by its global sections,

(4.39) degDΨ⁡(XΣ)=(DΨn)=n!​volM⁡(ΔΨ).\deg_{D_{\Psi}}(X_{\Sigma})=(D_{\Psi}^{n})=n!\operatorname{vol}_{M}(\Delta_{\Psi}).

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