2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97699The Galilean invariance in three dimensional space-time is considered. It appears that the Galilei group in 2+1 dimensions posses a three-parameter family of projective representations. Their physical interpretation is discussed in some detail.9 pages, latex, no figuresHigh Energy Physics - Theorytext