A laser master equation is derived by introducing an appropriate relaxation operator which takes into account correctly the semi-classical part of laser evolution. The introduction of the relaxation operator is done systematically by making use of the general procedure of non-equilibrium thermo...

An axiomatic formulation of the thermo field dynamics (TFD) for spin systems is performed, and is applied to the relaxation process of single spin-12. The spin relaxation accompanied with a change of symmetry of the system is also investigated. The time evolution of an order parameter is...

The generating functional formulation of non-equilibrium thermo field dynamics (NETFD) is given. The results are compared with those obtained by Schwinger who introduced the forward and backward time axes in order to include the dissipation effect. The relation of NETFD to other closed time-path...