© 1995 by London Mathematical Society
© The London Mathematical Society
Decomposability of Reflexive Cycle Algebras
Mathematics Department, Murdoch University Murdoch, Western Australia 6150, Australia E-mail: harrison{at}csuvaxl.murdoch.edu.au
Department of Mathematics, Edith Cowan University Perth, Western Australia 6050, Australia E-mail: u.mueller{at}cowan.edu.au
Received 19 January 1993. Revision received 14 June 1993.
We give, for each n
3, an example of a reflexive operator algebra
n with the following properties: (i) each finite rank operator with rank less than n – 1 is the sum of rank-one operators in
n, and (ii) there is an operator of rank n – 1 in
n which is not the sum of rank-one operators in
n. The invariant subspace lattice of
n is finite and distributive with 2n join-irreducible elements. We show also that the indecomposability of
n is related to the existence of a chordless cycle in a bipartite graph associated with
n.