The Standard Form of an E0-Semigroup

We show that the conjugacy classes of continuous semigroups of *-endomorphisms of B(H) that possess a pure, normal, absorbing state (i.e., standard E0-semigroups) are indexed by the orbits of the natural action of the group of local cocycles on the set of intertwining semigoups of isometries. We use this to show that, in passing from an arbitrary E0-semigroup α to a cocycle perturbation in standard form, the boundary representation is compressed to a hereditary subalgebra of the domain D(δα) of α.