Lemma 108.4.1. The diagonal of \mathcal{C}\! \mathit{oh}_{X/B} over B is affine and of finite presentation.
Proof. The representability of the diagonal by algebraic spaces was shown in Quot, Lemma 99.5.3. From the proof we find that we have to show \mathit{Isom}(\mathcal{F}, \mathcal{G}) \to T is affine and of finite presentation for a pair of finitely presented \mathcal{O}_{X_ T}-modules \mathcal{F}, \mathcal{G} flat over T with support proper over T. This was discussed in Section 108.3. \square
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