ScalingStacks

Proposition 3.7 . [038R]

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Proposition 3.7.

Under the hypotheses from 3.6, the model function ff is θ\theta-psh if and only if FF satisfies for all x∈Δ≔S⁡(𝒳)x\in\Delta\coloneqq S(\mathscr{X})

(3.1) ∑ν∈Tx​(Δ)wx​(ν)​λx,ν​(F)+deg⁡(θ|𝒞x)≥0,\displaystyle\sum_{\nu\in T_{x}(\Delta)}w_{x}(\nu)\lambda_{x,\nu}(F)+\deg(\theta|_{\mathcal{C}_{x}})\geq 0,

where ν\nu ranges over the set Tx​(Δ)T_{x}(\Delta) of outgoing tangent directions at xx. Here, λx,ν​(F)\lambda_{x,\nu}(F) denotes the slope of FF at xx along ν\nu and we have the weight wx(ν)≔[K~(pν):K~]w_{x}(\nu)\coloneqq[\tilde{K}(p_{\nu}):\tilde{K}] for the singularity pνp_{\nu} of 𝒳s\mathscr{X}_{s} corresponding to the edge of S⁡(𝒳)S(\mathscr{X}) at xx in the direction of ν\nu. Moreover, if xx is a vertex of S⁡(𝒳)S(\mathscr{X}), then 𝒞x\mathcal{C}_{x} denotes the corresponding irreducible component 𝒞x\mathcal{C}_{x} of 𝒳s\mathscr{X}_{s} and if xx is not a vertex, then deg⁡(θ|𝒞x)≔0\deg(\theta|_{\mathcal{C}_{x}})\coloneqq 0.

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