Computing K-theory and Ext for graph C*-algebras

الأصل · EN

K-theory and Ext are computed for the C*-algebra C*(E) of any countable directed graph E. The results generalize the K-theory computations of Raeburn and Szymanski and the Ext computations of Tomforde for row-finite graphs. As a consequence, it is shown that if A is a countable 0,1 matrix and Eₐ is the graph obtained by viewing A as a vertex matrix, then C*(Eₐ) is not necessarily Morita equivalent to the Exel-Laca algebra Oₐ.