Vertex projective module of a path algebra

ID: vertex-projective-module-of-a-path-algebra

The vertex projective module of a path algebra has at vertex the span of paths from to . Each arrow appends itself to such paths. It is a projective module because it is a summand of the free module . Its endomorphism ring is , acting by right multiplication. The closed-path corner of a path algebra is a domain, so this ring has no nontrivial idempotents and is indecomposable. Directed cycles may make these projectives infinite-dimensional.

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