2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59737A systematic exposition is given of the theory of invariant differential operators on a not necessarily reductive homogeneous space. This exposition is modelled on Helgason's treatment of the general reductive case and the special non-reductive case of the space of horocycles. As a final application the differential operators on (not a priori reductive) isotropic pseudo-Riemannian spaces are characterized.11 pages, electronic version of old 1981 reportRepresentation Theory43A85 (primary), 17B35, 22E30, 58J70 (secondary)text