De Haan, M.; George, C.; Mayné, F. - In: Physica A: Statistical Mechanics and its Applications 92 (1978) 3, pp. 584-598
The Friedrichs model of an unstable particle provides us with a non-trivial example of a dynamical system with a continuous spectrum. The non-unitary transformation operator which leads in our approach to a semi-group description of the time evolution of the system has been constructed in...