2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/202565We suggest a mechanism explaining the origin of three generations of the Standard Model fermions from one generation in a higher-dimensional theory. Four-dimensional fermions appear as zero modes trapped in the core of a topological defect with topological number three. We discuss hierarchical pattern of masses and mixings which arises in these models.19 pages, no figures; v.2: references added, main text unchangedHigh Energy Physics - Phenomenologytext