Skip to main content
2 of 2
added 331 characters in body
Jianrong Li
  • 6.2k
  • 2
  • 21
  • 34

Auslander-Reiten sequence and projective covers

Let $R$ be an Artin algebra and let $0 \to A \to B \to C \to 0$ be an Auslander-Reiten sequence of finitely generated left $R$-modules. Is it always true that the projective cover of $B$ equals to the direct sum of the projective cover of $A$ and the projective cover of $C$? Thank you very much.

Edit: I would also like to know the following.

Let $A \to B \to C$ ($B$ can be a direct sum of indecomposable modules) be a mesh in an Auslander-Reiten quiver. Is it true that the projective cover of $B$ is isomorphic to the direct sum of the projective cover of $A$ and the projective cover of $C$?

Thank you very much.

Jianrong Li
  • 6.2k
  • 2
  • 21
  • 34