Mathematical problems of irreversible statistical mechanics for quantum systems. II: On the singularities of (ψ(z) - Z)-1 and the pseudo-Markovian equation. Application to Lee model

We study in the frame of the superspace of the Hilbert-Schmidt operators the contributions of some complex singularities of the analytic continuation of (ψ(z) - z)- 1 to the diagonal part of the solution of the Liouville-von Neumann equation. Under some conditions, the θ̃ operator of the pseudo-Markovian master equation can be explicitly constructed. It is necessary to specify the diagonal representation and the class of initial conditions having regularity properties. This Hilbertian structure does not allow the construction of a closed subspace which reduces the Liouville-von Neumann operator L, giving an exact irreversible subdynamics; more elaborate mathematical structures are therefore necessary. The above methods are illustrated in the case of the Lee model. © 1982 American Institute of Physics.SCOPUS: ar.j