2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/93395In analogy to Gamow vectors describing resonance states from first order S-matrix poles, one can define Gamow vectors from higher order poles of the S-matrix. With these vectors we are going to discuss a density operator that describes exponentially decaying resonances from higher order poles.4 pages, no figures, uses group21.sty (included); to appear in GROUP21 proceedings vol. 1, H.-D. Doebner et al., eds., World Scientific, SingaporeQuantum Physicstext