ScalingStacks

Proof. [02SA]

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Proof.

In both cases, the fact that (a) implies (b) and that (b) implies (c) is clear. The fact that (c) implies (d) follows from equation (4.93). The fact that (1d) implies (1a) is [KKMS73, Β§IV.3(k)].

Finally, we prove that (2d) implies (2a). Let ψ\psi be an H-lattice concave function. Each pair (m,l)∈M~(m,l)\in{\widetilde{M}} defines a rational section Ο–l​χm​sψ\varpi^{l}\chi^{m}s_{\psi} of DψD_{\psi}. The section is regular if and only if the function m⁑(u)+lm(u)+l lies above ψ\psi. Moreover, for a polyhedron Ξ›βˆˆΞ \Lambda\in\Pi, this section does not vanish on 𝒳Λ{\mathcal{X}}_{\Lambda} if and only if ψ⁑(u)=m⁑(u)+l\psi(u)=m(u)+l for all uβˆˆΞ›u\in\Lambda. Therefore, the affine pieces of the graph of ψ\psi define a set of global sections that generate π’ͺ⁑(Dψ)\mathcal{O}(D_{\psi}). ∎

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