Projective irreducible unitary representations of the Schrodinger group with a nontrivial factor

A classification and a realization are given of the projective irreducible unitary representations of the Schroedinger group which have a nontrivial factor, i.e., representations which are not equivalent to true representations. The connection between some of these representatives and the realizations found previously on spaces of solutions of Schroedinger equations is then established. 6 references