ScalingStacks

Proof. [016G]

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Proof.

It follows from (4.4) and (4.5) that τ\tau is a bijection. Since XArAnX_{A_{r}}^{\mathrm{An}} is compact and X𝔻¯rhybX_{\overline{{\mathbb{D}}}_{r}}^{\mathrm{hyb}} is Hausdorff, it only remains to prove that τ\tau is continuous. It suffices to show that the corresponding map τ𝒳:XArAn→𝒳𝔻¯rhyb\tau_{\mathcal{X}}\colon X_{A_{r}}^{\mathrm{An}}\to{\mathcal{X}}^{\mathrm{hyb}}_{\overline{{\mathbb{D}}}_{r}} is continuous for a given snc model 𝒳{\mathcal{X}}. For this, in turn, it suffices to show that Log𝒳∘τ𝒳\operatorname{Log}_{\mathcal{X}}\circ\tau_{\mathcal{X}} is continuous near the central fiber.

Consider a coordinate chart (𝒰,z)({\mathcal{U}},z) adapted to 𝒳0{\mathcal{X}}_{0} in the sense of §2.2. Let E0,…,EpE_{0},\dots,E_{p} be the irreducible components of 𝒳0{\mathcal{X}}_{0} intersecting 𝒰{\mathcal{U}}. Let 𝒰^⊂XArAn\hat{\mathcal{U}}\subset X_{A_{r}}^{\mathrm{An}} be the set of seminorms satisfying |zi|<1|z_{i}|<1 for 0≤i≤p0\leq i\leq p. Then we have

Log𝒳∘τ𝒳\displaystyle\operatorname{Log}_{\mathcal{X}}\circ\tau_{\mathcal{X}} =(log⁡|zi|∞log⁡|t|∞)0≤i≤p+O⁡((log⁡|t|∞)−1)\displaystyle=\left(\frac{\log|z_{i}|_{\infty}}{\log|t|_{\infty}}\right)_{0\leq i\leq p}+O((\log|t|_{\infty})^{-1})
=(log⁡|zi|−1)0≤i≤p+O⁡((log⁡|t|∞)−1)\displaystyle=(\log|z_{i}|^{-1})_{0\leq i\leq p}+O((\log|t|_{\infty})^{-1})

on 𝒰^∖π−1​(0)\hat{\mathcal{U}}\setminus\pi^{-1}(0). Now the function (log⁡|zi|−1)i(\log|z_{i}|^{-1})_{i} is continuous on 𝒰^\hat{\mathcal{U}} with values in the simplex σ=ℝ+p+1∩{∑0pbiwi=1}⊂Δ(𝒳)\sigma={\mathbb{R}}_{+}^{p+1}\cap\{\sum_{0}^{p}b_{i}w_{i}=1\}\subset\Delta({\mathcal{X}}). This completes the proof, since we can cover a neighborhood of the central fiber in XArAnX_{A_{r}}^{\mathrm{An}} with sets of the type 𝒰^\hat{{\mathcal{U}}}. ∎

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