Published online by Cambridge University Press: 20 November 2018
Let be a fixed separable, infinite dimensional complex Hilbert space, and let
(
) denote the algebra of all (bounded, linear) operators on
. The ideal of all compact operators on
will be denoted by
and the canonical quotient map from
(
) onto the Calkin algebra
(
)/
will be denoted by π.
Some open problems in the theory of extensions of C*-algebras (cf. [1]) have recently motivated an increasing interest in the class of all operators in (
) whose self-commuta tor is compact.