Decoherence and classical predictability of phase space histories

摘要: We consider the decoherence of phase-space histories in quantum Brownian motion models, consisting a particle moving under a potential V(x) contact with heat bath temperature T and dissipation constant g in Markovian regime. The are described by quasiprojectors Gaussian density matrices smeared over large cells characterized size @G# phase-space cell together [M] margin ~the region at boundary G which Weyl symbol the projector goes from 1 to 0!. generalize earlier results Hagedorn show that an initial Gaussian density matrix remains approximately nonunitary time evolution deriving bound giving validity of this approximation. Following work Omne`s @J. Stat. Phys. 51, 351 ~1989!# we use result to compute projectors master equation histories of samplings decohere, probabilities for these peaked about classical dissipative evolution, but element unpredictability is reflected increase of margin.