  With the use of two kinds of boson operators, a new boson representation of
the su(2)-algebra is proposed. The basic idea comes from the pseudo
su(1,1)-algebra recently given by the present authors. It forms a striking
contrast to the Schwinger boson representation of the su(2)-algebra which is
also based on two kinds of bosons. This representation may be suitable for
describing time-dependence of the system interacting with the external
environment in the framework of the thermo field dynamics formalism, i.e., the
phase space doubling. Further, several deformations related to the
su(2)-algebra in this boson representation are discussed. On the basis of these
deformed algebra, various types of time-evolution of a simple boson system are
investigated.
