Projective representation of the Galilei group for classical and quantum–classical systems*

Abstract A physically relevant unitary irreducible non-projective representation of the Galilei group is possible in Koopman–von Neumann formulation classical mechanics. This characterized by vanishing central charge algebra. contrast to quantum case where mass plays role charge. Here we show, direct construction, that mechanics also allows for a projective We extend result certain kind quantum–classical hybrid systems.