Algebraic theory of product integrals in quantum stochastic calculus

Motivated by the search for solutions of the quantum Yang-Baxter equation, an algebraic theory of quantum stochastic product integrals is developed. The product integrators are formal power series in an indeterminate h whose coefficients are elements of the Lie algebra L labelling the usual integrators of a many-dimensional quantum stochastic calculus. The product integrals are also formal power series in h, whose coefficients are finite iterated additive stochastic integrals which act on the exponential domain in the Fock space of the calculus and which represent elements of the universal enveloping algebra U of L. They obey a multiplication rule suggested by the quantum Ito product formula, and are characterized among all such formal power series by a grouplike property. (C) 2000 American Institute of Physics. [S0022-2488(00)02107-1].