Lemma 71.16.4. Let $S$ be a scheme and let $X$ be an algebraic space over $S$. Let $\mathcal{E}$ be a quasi-coherent $\mathcal{O}_ X$-module. There is a bijection
\[ \left\{ \begin{matrix} \text{sections }\sigma \text{ of the }
\\ \text{morphism } \mathbf{P}(\mathcal{E}) \to X
\end{matrix} \right\} \leftrightarrow \left\{ \begin{matrix} \text{surjections }\mathcal{E} \to \mathcal{L}\text{ where}
\\ \mathcal{L}\text{ is an invertible }\mathcal{O}_ X\text{-module}
\end{matrix} \right\} \]
In this case $\sigma $ is a closed immersion and there is a canonical isomorphism
\[ \mathop{\mathrm{Ker}}(\mathcal{E} \to \mathcal{L}) \otimes _{\mathcal{O}_ X} \mathcal{L}^{\otimes -1} \longrightarrow \mathcal{C}_{\sigma (X)/\mathbf{P}(\mathcal{E})} \]
Both the bijection and isomorphism are compatible with base change.
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