Degrees and composition of irreducible morphisms in almost presectional paths

CHAIO CLAUDIA

Algebras and Representation Theory

SPRINGER

Lugar: Berlin; Año: 2014 vol. 17 p. 407 - 432

1386-923X

We consider A to be an artin algebra. We characterize the irreducible morphisms of left degree two. We study the non-zero composition of irreducible morphisms in almost pre-sectional paths. As a consequence, we get a complete description of when the composition of three irreducible morphisms between indecomposable modules is a non-zero morphism in the fourth power of the radical. We also determine the degree of irreducible morphism between indecomposable modules in Auslander-Reiten components, with almost split sequences with at most two middle terms.