Leavitt path algebras of separated graphs
arXiv:1004.4979
Abstract
The construction of the Leavitt path algebra associated to a directed graph is extended to incorporate a family consisting of partitions of the sets of edges emanating from the vertices of . The new algebras, , are analyzed in terms of their homology, ideal theory, and K-theory. These algebras are proved to be hereditary, and it is shown that any conical abelian monoid occurs as the monoid $\mon{L_K(E,C)}$ of isomorphism classes of finitely generated projective modules over one of these algebras. The lattice of trace ideals of is determined by graph-theoretic data, namely as a lattice of certain pairs consisting of a subset of and a subset of . Necessary conditions for $\mon{L_K(E,C)}$ to be a refinement monoid are developed, together with a construction that embeds in a separated graph such that $\mon{L_K(E_+,C^+)}$ has refinement.
56 pages. Final version, to appear in J. reine angew. Math. Minor changes