ScalingStacks

Démonstration. [01J4]

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Démonstration.

Let L¯0\overline{L}_{0} be the trivial line bundle with global section s0=1s_{0}=1 and metric defined by φ=log⁡‖s0‖−1\varphi=\log\left\|{s_{0}}\right\|^{-1}. Let s1=ss_{1}=s and, for 2≤j≤k2\leq j\leq k, let sjs_{j} be an invertible meromorphic section of LjL_{j}. Since div⁡(s0|Z)=0\operatorname{div}(s_{0}|_{\mathrm{Z}})=0,

(div^⁡(s0)​…​div^⁡(sk)|Z)=∫Xφ​c1​(L¯1)​…​c1​(L¯k)​δZ(\mathop{\widehat{\operatorname{div}}}(s_{0})\dots\mathop{\widehat{\operatorname{div}}}(s_{k})|\mathrm{Z})=\int_{\mathrm{X}}\varphi c_{1}(\overline{L}_{1})\dots c_{1}(\overline{L}_{k})\delta_{\mathrm{Z}}

and

(div^⁡(s0)​div^⁡(s2)​…​div^⁡(sk)|div⁡(s|Z))=∫Xφ​c1​(L¯2)​…​c1​(L¯k)​δdiv⁡(s|Z)(\mathop{\widehat{\operatorname{div}}}(s_{0})\mathop{\widehat{\operatorname{div}}}(s_{2})\dots\mathop{\widehat{\operatorname{div}}}(s_{k})|\operatorname{div}(s|_{\mathrm{Z}}))=\int_{\mathrm{X}}\varphi c_{1}(\overline{L}_{2})\dots c_{1}(\overline{L}_{k})\delta_{\operatorname{div}(s|\mathrm{Z})}

One the other hand, the symmetry of the local height pairing implies that

(div^⁡(s0)​…​div^⁡(sk)|Z)\displaystyle(\mathop{\widehat{\operatorname{div}}}(s_{0})\dots\mathop{\widehat{\operatorname{div}}}(s_{k})|\mathrm{Z}) =(div^⁡(s1)​div^⁡(s0)​…​div^⁡(sk)|Z)\displaystyle=(\mathop{\widehat{\operatorname{div}}}(s_{1})\mathop{\widehat{\operatorname{div}}}(s_{0})\dots\mathop{\widehat{\operatorname{div}}}(s_{k})|\mathrm{Z})
=(div^⁡(s0)​div^⁡(s2)​…​div^⁡(sk)|div⁡(s|Z))\displaystyle=(\mathop{\widehat{\operatorname{div}}}(s_{0})\mathop{\widehat{\operatorname{div}}}(s_{2})\dots\mathop{\widehat{\operatorname{div}}}(s_{k})|\operatorname{div}(s|_{\mathrm{Z}}))
+∫Xlog‖s‖−1c1(L¯0)c1(L¯2)…c1(L¯k)δZ.\displaystyle\hskip 85.35826pt{}+\int_{\mathrm{X}}\log\left\|{s}\right\|^{-1}c_{1}(\overline{L}_{0})c_{1}(\overline{L}_{2})\dots c_{1}(\overline{L}_{k})\delta_{\mathrm{Z}}.

Combining these equations, we obtain the claim. ∎

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