The Langevin equation derived by Shibata and Hashitsume with the help of the projection operator formula is shown to be the stochastic differential equation of the Ito type. From their derivation, it is natural to interpret it as that of the Stratonovich type. However, comparing the...

The development of non-equilibrium thermo field dynamics, called NETFD in abbreviation, was started in 1983 based on the damping theory in Liouville space. It has progressed considerably since then. Especially, the structural similarity between the framework of NETFD and the framework of the...