2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/50154Rotation symmetry is less constraining than space-time symmetry. The free electron propagator is a projection operator that we show can be constructed from rotation symmetric projection operators. Rotation-based identifications of time, space, energy, momentum, polarization matrices, and the positron hypothesis are determined by the constraints that turn rotation symmetric projection operators into the electron propagator. PACS: 11.30.-j, 11.30.Cp, and 03.65.Fd15 pages, no figures, LaTexHigh Energy Physics - Theorytext