ScalingStacks

Lemma 2.1 . [007S]

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Lemma 2.1.

(Good test function) Given the divisor E0E_{0}, we can choose a C2C^{2} test function vv on XtX_{t} such that the following hold uniformly for small t≠0t\neq 0:

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    vv is zero for h≥δh\geq\delta.

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    Globally 0≤v≤−log⁡|t|0\leq v\leq-\log|t|.

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    For any divisor EjE_{j} intersecting E0E_{0}, there is a subset of Ej0E_{j}^{0} with measure at least C2C_{2} on which −1​∂∂¯​v∧ω𝒳|Xtn−1≥C3​ω𝒳|Xtn\sqrt{-1}\partial\bar{\partial}v\wedge\omega_{\mathcal{X}}|_{X_{t}}^{n-1}\geq C_{3}\omega_{\mathcal{X}}|_{X_{t}}^{n}.

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    For C4​|t|2≤h≤δC_{4}|t|^{2}\leq h\leq\delta, the form −1​∂∂¯​v∧ω𝒳|Xtn−1≥0\sqrt{-1}\partial\bar{\partial}v\wedge\omega_{\mathcal{X}}|_{X_{t}}^{n-1}\geq 0.

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    For h≤C4​|t|2h\leq C_{4}|t|^{2}, the form −1​∂∂¯​v∧ω𝒳|Xtn−1≥−C5​ω𝒳|Xtn\sqrt{-1}\partial\bar{\partial}v\wedge\omega_{\mathcal{X}}|_{X_{t}}^{n-1}\geq-C_{5}\omega_{\mathcal{X}}|_{X_{t}}^{n}.

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