The Stacks project

Lemma 12.5.10. Let $\mathcal{A}$ be an abelian category. Let $0 \to A \to B \to C \to 0$ be a short exact sequence.

  1. Given a morphism $s : C \to B$ right inverse to $B \to C$, there exists a unique $\pi : B \to A$ such that $(s, \pi )$ splits the short exact sequence as in Definition 12.5.9.

  2. Given a morphism $\pi : B \to A$ left inverse to $A \to B$, there exists a unique $s : C \to B$ such that $(s, \pi )$ splits the short exact sequence as in Definition 12.5.9.

Proof. Omitted. $\square$

Comments (2)

Comment #8745 by Anonymous on

If " is left inverse to " means that is the identity (where means "apply first"), then I think "left" and "right" should be switched in this lemma.

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  • 9 comment(s) on Section 12.5: Abelian categories

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