The Functor \(K_{0}^{\operatorname {gr}}\) is Full and only Weakly Faithful

Abstract

The Graded Classification Conjecture states that the pointed \(K_{0}^{\operatorname {gr}}\)-group is a complete invariant of the Leavitt path algebras of finite graphs when these algebras are considered with their natural grading by \(\mathbb {Z}\). The strong version of this conjecture states that the functor \(K_{0}^{\operatorname {gr}}\) is full and faithful when considered on the category of Leavitt path algebras of finite graphs and their graded homomorphisms modulo conjugations by invertible elements of the zero components. We show that the functor \(K_{0}^{\operatorname {gr}}\) is full for the unital Leavitt path algebras of countable graphs and that it is faithful (modulo specified conjugations) only in a certain weaker sense.