| The “system+bath” approach is applied to study quantum dynamics in condensed phase matter. In this approach one selects the subsystem of interest and includes approximately the effects of the remaining part of the system, or “bath”, on the subsystem dynamics. Such a subsystem is usually called a quantum dissipative system. Three novel methods are introduced for the simulation of the dynamics of quantum dissipative systems: a memory equation algorithm, its combination with mixed quantum-classical methods, and a quasiclassical method. The first two are based on the influence functional approach within Feynman's path-integral formulation of quantum dynamics. Our methods are much more efficient than other methods based on this approach. In practice, the influence functional approach is restricted to a harmonic bath. In contrast, a quasiclassical method is applicable to both a harmonic and a spin bath. The difference between two bath models is discussed. |
