The Stacks project

Definition 12.28.5. Let $\mathcal{A}$ be an abelian category. We say that $\mathcal{A}$ has functorial projective surjections if there exists a functor

\[ P : \mathcal{A} \longrightarrow \text{Arrows}(\mathcal{A}) \]

such that

  1. $t \circ P = \text{id}_\mathcal {A}$,

  2. for any object $A \in \mathop{\mathrm{Ob}}\nolimits (\mathcal{A})$ the morphism $P(A)$ is surjective, and

  3. for any object $A \in \mathop{\mathrm{Ob}}\nolimits (\mathcal{A})$ the object $s(P(A))$ is an projective object of $\mathcal{A}$.

We will denote such a functor by $A \mapsto (P(A) \to A)$.

Comments (0)

There are also:

  • 2 comment(s) on Section 12.28: Projectives

Post a comment

Your email address will not be published. Required fields are marked.

In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).

Unfortunately JavaScript is disabled in your browser, so the comment preview function will not work.

All contributions are licensed under the GNU Free Documentation License.




In order to prevent bots from posting comments, we would like you to prove that you are human. You can do this by filling in the name of the current tag in the following input field. As a reminder, this is tag 013F. Beware of the difference between the letter 'O' and the digit '0'.



View Definition 12.28.5 as pdf