Path integrals for open quantum systems: General theory and dynamical simulation

The influence functional method for a particle interacting with a thermal bath is outlined. The cases of factorizing and of correlated initial states of the system-plus-reservoir complex are briefly discussed. The method is applied to the dissipative two-level system. The exact formal solutions for conditional probabilities and the equilibrium correlation function are given. We then review the recent progress towards the solution of the sign problem in the numerical simulation of real-time functional integrals, and present some results for the equilibrium correlation function of the spin-boson model. (author). 21 refs, 6 figs