Models for dissipation in quantum mechanics

N. G. van Kampen

Jürg Fröhlich, Alessandro Pizzo

This note starts with a recapitulation of what people call the ``Measurement Problem'' of Quantum Mechanics (QM). The dissipative nature of the quantum-mechanical time-evolution of averages of states over large ensembles of identical isolated systems consisting of matter interacting with the radiation field is discussed and shown to correspond to a stochastic time-evolution of states of individual systems. The importance of dissipation for the successful completion of measurements is highlighted. To conclude, a solution of the ``Measurement Problem'' is sketched in an idealized model of a double-slit experiment.

A. H. Castro Neto, A. O. Caldeira

We propose a new model for studying dissipation in quantum-mechanical systems. The mechanism of dissipation is solely due to the scattering of the environment excitations by the particle of interest. We treat the problem via the functional integral formalism. It is shown that the model gives a damping parameter which is temperature dependent.