Reduction of a Boson Subsystem up to the Lowest Order

Abstract

Derivation of a master equation is given in the case where a Boson subsystem can be eliminated besides reservoirs by using the time-convolution-less formulation of the damping theory within the conventional treatment, up to the lowest order expansion of the “kinetic coefficient” with respect to the coupling constant between the Boson subsystem and the remaining ones. Useful diagramatic expansion of Liouville operators, formula for the elimination of Boson operators and algebraic formulae of the spin coherent representation are given in Appendices.