2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97436Different structures of master-equation used for the description of decoherence of a microsystem interacting through collisions with a surrounding environment are considered and compared. These results are connected to the general expression of the generator of a quantum dynamical semigroup in presence of translation invariance recently found by Holevo.10 pages, latex, no figures, to appear in Int. J. Theor. PhysQuantum Physicstext