Remarks on Derivations on Maximal Triangular Operator Algebras

This note concerns bounded derivations on maximal triangular operator algebras on a Hilbert space. Given any bounded derivation $\delta$ on a maximal triangular algebra whose invariant lattice is continuous at 1, an operator which is shown to implement $\delta$ is constructed explicitly. For a general reducible maximal triangular algebra the same construction yields an operator which is shown to implement any $\delta$, if and only if $\delta$ obeys an additional triple product rule. This work is based on unpublished parts of the author's dissertation [19] and describes a variant of the proof of a more general result in [21] and is thus in effect a footnote to that work. To the best of the author's knowledge the constructive proof and triple product rule have not appeared elsewhere. The work here is not set in the context of the large body of subsequent research, and no claims are made regarding its relationship to later developments.