2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/215150In this paper we consider a quantum open system and treat the master equation with some restricted dissipator which consists of a set of projection operators (projectors). The exact solution is given under the commutable approximation (in our terminology). This is the first step for constructing a general solution.Latex ; 7 pages ; no figureQuantum PhysicsMathematical Physicstext