Many of the examples of above are of the type: A subsystem (or chromophore) interacts with an environment, which leads to energy and phase relaxation in the system. These system-bath problems can be treated in various ways. In quantum dynamics, we often use reduced density matrix theory, by solving an open-system Liouville-von Neumann (LvN) equation either with or without the Markov approximation and by direct matrix propagation. LvN equations can also be solved by stochastic wave- packet methods instead. An alternative approach is the solution of the full system-bath, time-dependent Schrödinger equation, by approximate quantum wavepacket methods. Examples are the MCTDH (Multi-Configurational Time-Dependent Hartree), the LCSA (Local Coherent State Approximation), and TDSCF (Time-Dependent Self-Consistent-Field) methods. Further, quantum-classical dynamics or molecular dynamics with friction (Langevin dynamics), can be employed. Method-oriented examples of our work are (numbering refers to publication list):
- Direct, reduced density matrix theory[12,14,18,26,32,39,48,50,54,81,88,96,97,117,138].
- Stochastic, dissipative, or coupled wavepacket methods[21,29,35,43,59,71,100,134].
- Approximate wavepacket methods: MCTDH, LCSA, TDSCF[44,77,78,83,112,138].
- Quantum-classical dynamics [31,44] and Langevin dynamics[31,100,118,134].