We construct a sequence of concordance invariants for classical links, which depend on the peripheral isomorphism type of the nilpotent quotients of the link fundamental group. The terminology stems from the fact that we replace the Magnus expansion in the definition of Milnor's μfalse¯‐invariants by the similar Campbell–Hausdorff expansion. The main point is that we introduce a new universal indeterminacy, which depends only on the number of components of the link. The Campbell–Hausdorff invariants are new, effectively computable and can efficiently distinguish (unordered and unoriented) isotopy types of links, as we indicate on several families of closed braid examples. They also satisfy certain natural dependence relations, which generalize well‐known symmetries of the μfalse¯‐invariants. 1991 Mathematics Subject Classification: 81S25, 46L10, 46L50, 47A60.

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In the calculus of Hudson and Parthasarathy we show the existence of a solution to the quantum stochastic evolution equationfor a class of unbounded operators L,,..., L 4 in the initial space, and show that the necessary and sufficient condition that U be a unitary process is the same as in the case that L , , . . . , L 4 are bounded.Applications of the vacuum conditional expectation to U give rise to strongly continuous semigroups and their generators in the initial space, and to ultraweakly continuous completely positive semigroups and their generators in the von Neumann algebra of the initial space.