Lemma 37.62.23. Let Z \to Y \to X be formally unramified morphisms of schemes. Assume that Z \to Y is a local complete intersection morphism. The exact sequence
of Lemma 37.7.12 is short exact.
Lemma 37.62.23. Let Z \to Y \to X be formally unramified morphisms of schemes. Assume that Z \to Y is a local complete intersection morphism. The exact sequence
of Lemma 37.7.12 is short exact.
Proof. The question is local on Z hence we may assume there exists a factorization Z \to \mathbf{A}^ n_ Y \to Y of the morphism Z \to Y. Then we get a commutative diagram
As Z \to Y is a local complete intersection morphism, we see that Z \to \mathbf{A}^ n_ Y is a Koszul-regular immersion. Hence by Divisors, Lemma 31.21.6 the sequence
is exact and locally split. Note that i^*\mathcal{C}_{Y/X} = (i')^*\mathcal{C}_{\mathbf{A}^ n_ Y/\mathbf{A}^ n_ X} by Lemma 37.7.7 and note that the diagram
is commutative. Hence the lower horizontal arrow is a locally split injection. This proves the lemma. \square
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