Classical fluctuations in dissipative quantum systems.

  title={Classical fluctuations in dissipative quantum systems.},
  journal={Physical review. D, Particles and fields},
  volume={33 12},
Dissipative quantum systems such as an unstable field, thermal field, and cosmological particle production are investigated. Equations of motion for each appropriate mean field are revealed to be Langevin type. The derived correlation of the random field turns out not to be Gaussian nor white in general. A relation between a popular quantum average and the statistical correlation is also clarified.