Physical description of decay processes

A dynamical formulation of quasi-particles corresponding to complex poles of Green's functions has been provided in the frame of "Liapounov" transformations in a superoperator formalism. In this formalism, two different superoperators are associated with the hamiltonian, on the one hand an energy superoperator H, and on the other, an evolution superoperator L. In the case of systems with continuous spectrum, it is possible to diagonalize the transform of H, the diagonal elements being the energies found by the Green's functions methods. This can be achieved without diagonalizing at the same time, the transform of L: the inverse lifetimes and the collision processes are obtained in this way. We show here on the Friedrichs model, that we can specify uniquely such a transformation in agreement with our previous "new quantum rules for dissipative systems". This method can be generalized to more complex systems. © 1981.SCOPUS: ar.j