  A pseudo su(1,1)-algebra is formulated as a possible deformation of the
Cooper-pair in the su(2)-algebraic many-fermion system. With the aid of this
algebra, it is possible to describe behavior of individual fermions which are
generated as the result of interaction with the external environment. The form
presented in this paper is a generalization of a certain simple case developed
recently by the present authors. Basic idea follows the su(1,1)-algebra in the
Schwinger boson representation for treating energy transfer between the
harmonic oscillator and the external environment. Hamiltonian is given under
the idea of the phase space doubling in the thermo-field dynamics formalism and
the time-dependent variational method is applied to this Hamiltonian. Its trial
state is constructed in the frame deformed from the BCS-Bogoliubov approach to
the superconductivity. Several numerical results are shown.

Nuclear Theory