ScalingStacks

Verified tagged author-source HTML · 1904.03696v1 · cited publication edition alignment unverified.

00L4

Proposition 3.21. Let n∈ℕn\in\mathbb{N} be an integer such that L⊗nL^{\otimes n} is globally generated. Let {sn,j}j∈{0,…,dn}\{s_{n,j}\}_{j\in\{0,\dots,d_{n}\}} be a basis of Vn​(L)V_{n}(L). Let ∥⋅∥n\lVert\mathord{\cdot}\rVert_{n} be a ultrametric norm on Vn​(L)V_{n}(L) with respect to which this basis is orthogonal. Let (x,e1∨​(x))∈T​o​t​(L∨)(x,e_{1}^{\vee}(x))\in Tot(L^{\vee}) and z∈(Spec⁡V∙​(L))anz\in(\spec V_{{\scriptscriptstyle\bullet}}(L))^{\mathrm{an}} be it image under p​(𝟎)anp(\boldsymbol{0})^{\mathrm{an}}, then (x,e1∨​(x))∈𝔻¯∨​(L,1n​FS​(∥⋅∥n))(x,e_{1}^{\vee}(x))\in\overline{\mathbb{D}}^{\vee}(L,\frac{1}{n}\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n})) (resp.𝔻∨​(L,1n​FS​(∥⋅∥n))\mathbb{D}^{\vee}(L,\frac{1}{n}\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n}))) if and only if

∀j∈{0,…,dn},|sn,j​(z)|≤∥sn,j∥n​(resp.<∥sn,j∥n).\forall j\in\{0,\dots,d_{n}\},\ \lvert s_{n,j}(z)\rvert\leq\lVert s_{n,j}\rVert_{n}\ (\text{resp.}<\lVert s_{n,j}\rVert_{n}).

In particular, the image of 𝔻∨​(L,1n​FS​(∥⋅∥n))\mathbb{D}^{\vee}(L,\frac{1}{n}\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n})) under p​(𝟎)anp(\boldsymbol{0})^{\mathrm{an}} is an open subset in (Spec⁡V∙​(L))an(\spec V_{{\scriptscriptstyle\bullet}}(L))^{\mathrm{an}}.

00L5

Proof. The assertion is clear if e1​(x)=0e_{1}(x)=0. For e1​(x)≠0e_{1}(x)\neq 0, let en​(x)=e1⊗n​(x)e_{n}(x)=e_{1}^{\otimes n}(x), note that

|e1∨​(x)|1n​FS​(∥⋅∥n)∨=(|en∨​(x)|FS​(∥⋅∥n)∨)1n.\lvert e_{1}^{\vee}(x)\rvert_{\frac{1}{n}\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n})^{\vee}}=(\lvert e_{n}^{\vee}(x)\rvert_{\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n})^{\vee}})^{\frac{1}{n}}.

By Corollary 3.15, one has

|en∨​(x)|FS​(∥⋅∥n)∨=max⁡{|en∨​(x)​(sn,j)|κ^​(x)⋅∥sn,j∥n−1}\lvert e_{n}^{\vee}(x)\rvert_{\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n})^{\vee}}=\max\Big\{\lvert e_{n}^{\vee}(x)(s_{n,j})\rvert_{\widehat{\kappa}(x)}\cdot\lVert s_{n,j}\rVert_{n}^{-1}\Big\}

so

|e1∨​(x)|1n​FS​(∥⋅∥n)∨=max⁡{|en∨​(x)​(sn,j)|κ^​(x)⋅∥sn,j∥n−1}1n.\lvert e_{1}^{\vee}(x)\rvert_{\frac{1}{n}\mathrm{FS}(\lVert\mathord{\cdot}\rVert_{n})^{\vee}}=\max\Big\{\lvert e_{n}^{\vee}(x)(s_{n,j})\rvert_{\widehat{\kappa}(x)}\cdot\lVert s_{n,j}\rVert_{n}^{-1}\Big\}^{\frac{1}{n}}.

Tautologically, one has

sn,j​(z)=(e1⊗n)∨​(x)​(sn,j)=en∨​(x)​(sn,j),s_{n,j}(z)=(e_{1}^{\otimes n})^{\vee}(x)(s_{n,j})=e_{n}^{\vee}(x)(s_{n,j}),

so the criterion holds. By these defining equations, it is easy to see that the image of the open dual unit disc bundle is an open set. ∎

Original mathematics by the credited authors. Source collection and HTML conversion remain in progress.