Published online by Cambridge University Press: 20 January 2009
We give a necessary and sufficient condition to determine when an operator in the nest algebra of doubly infinite block upper triangular operators factors through a diagonal projection. An example shows that this condition does not extend to more general nest algebras, but a similar criterion yields a description of the ideals of nest algebras generated by diagonal projections.
Both authors were partially supported by NSF grant DMS-9204811.