Hydrodynamic equations for mixed quantum states. I. General formulation

Quantum-mechanical hydrodynamic equations are considered for mixed quantum states, and the corresponding equations for pure quantum states are derived as a particular case. A generalization of the "quantum potential" of Bohmi an mechanics is formulated. In the mixed-state case, an infinite hierarchy of kinetic equations arises that may be truncated by introducing suitable a pproximations. The influence of dissipation on the kinetic equations is dis cussed. (C) 2001 American Institute of Physics.