2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/101027Demailly-Semple jets are studied using the invariant theory of non reductive groups. The geometric characterization of the 3-jets bundle in dimension 3 is given and provides a Riemann-Roch computation.25 pages, in french, final versionAlgebraic GeometryComplex Variables14L24; 32Q45text