ScalingStacks

Proof. [0275]

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Proof.

First let us see that |s|h​(x)≤|s|ℒ​(x)|s|_{h}(x)\leq|s|_{\mathscr{L}}(x) for s∈Hs\in H. Let ωξ\omega_{\xi} be a local basis of ℒ\mathscr{L} at ξ=r𝒳​(x)\xi=r_{\mathscr{X}}(x). If we set s=sξ​ωξs=s_{\xi}\omega_{\xi}, then

|s|ℒ​(x)=|sξ|x.|s|_{\mathscr{L}}(x)=|s_{\xi}|_{x}.

As sξ−1​s∈ℒξs_{\xi}^{-1}s\in\mathscr{L}_{\xi} and ℋ⊗𝔬k𝒪𝒳,ξ→ℒξ\mathscr{H}\otimes_{\mathfrak{o}_{k}}\mathscr{O}_{\mathscr{X},\xi}\to\mathscr{L}_{\xi} is surjective, there are l1,…,lr∈ℋl_{1},\ldots,l_{r}\in\mathscr{H} and a1,…,ar∈𝒪𝒳,ξa_{1},\ldots,a_{r}\in\mathscr{O}_{\mathscr{X},\xi} such that sξ−1​s=a1​l1+⋯+ar​lrs_{\xi}^{-1}s=a_{1}l_{1}+\cdots+a_{r}l_{r}. Therefore,

|sξ−1​s|h​(x)\displaystyle\left|s_{\xi}^{-1}s\right|_{h}(x) ≤max⁡{|a1​l1|h​(x),…,|ar​lr|h​(x)}\displaystyle\leq\max\left\{|a_{1}l_{1}|_{h}(x),\ldots,|a_{r}l_{r}|_{h}(x)\right\}
=max⁡{|a1|x​|l1|h​(x),…,|ar|x​|lr|h​(x)}≤1,\displaystyle=\max\left\{|a_{1}|_{x}|l_{1}|_{h}(x),\ldots,|a_{r}|_{x}|l_{r}|_{h}(x)\right\}\leq 1,

so that |s|h​(x)≤|sξ|x=|s|ℒ​(x)|s|_{h}(x)\leq|s_{\xi}|_{x}=|s|_{\mathscr{L}}(x), as required.

Next let us see that |l|ℒ​(x)≤‖l‖κ^​(x)|l|_{\mathscr{L}}(x)\leq\|l\|_{\hat{\kappa}(x)} for all l∈H⊗κ^​(x)l\in H\otimes\hat{\kappa}(x). By Proposition 1.9, (e1,…,er)(e_{1},\ldots,e_{r}) is an orthonormal basis of H⊗κ^​(x)H\otimes\hat{\kappa}(x) with respect to ‖.‖κ^​(x)\|\raisebox{1.72218pt}{.}\|_{\hat{\kappa}(x)}. Thus, if we set l=a1​e1+⋯+ar​erl=a_{1}e_{1}+\cdots+a_{r}e_{r} (a1,…,ar∈κ^​(x)a_{1},\ldots,a_{r}\in\hat{\kappa}(x)), then

|l|ℒ​(x)\displaystyle|l|_{\mathscr{L}}(x) ≤max⁡{|a1|x​|e1|ℒ​(x),…,|ar|x​|er|ℒ​(x)}\displaystyle\leq\max\{|a_{1}|_{x}|e_{1}|_{\mathscr{L}}(x),\ldots,|a_{r}|_{x}|e_{r}|_{\mathscr{L}}(x)\}
≤max⁡{|a1|x,…,|ar|x}=‖l‖κ^​(x).\displaystyle\leq\max\{|a_{1}|_{x},\ldots,|a_{r}|_{x}\}=\|l\|_{\hat{\kappa}(x)}.

Finally let us see that |s|ℒ​(x)≤|s|h​(x)|s|_{\mathscr{L}}(x)\leq|s|_{h}(x) for s∈Hs\in H. For ϵ>0\epsilon>0, we choose l∈H⊗κ^​(x)l\in H\otimes\hat{\kappa}(x) such that l⁡(x)=s⁡(x)l(x)=s(x) and ‖l‖κ^​(x)≤eϵ​|s|h​(x)\|l\|_{\hat{\kappa}(x)}\leq e^{\epsilon}|s|_{h}(x). Then, by the previous observation,

|s|ℒ​(x)=|l|ℒ​(x)≤‖l‖κ^​(x)≤eϵ​|s|h​(x).|s|_{\mathscr{L}}(x)=|l|_{\mathscr{L}}(x)\leq\|l\|_{\hat{\kappa}(x)}\leq e^{\epsilon}|s|_{h}(x).

Thus the assertion follows. ∎

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