2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42704We review the experimental evidence for a net baryon density in cosmology, and the theoretical mechanism for producing it, called leptogenesis, which relies on the creation of a lepton asymmetry at an intermediate step. The naturality of this mechanism and its possible relations with neutrino oscillations are outlined.11 pages, 6 figures; presented at the XXXVIII Rencontres de Moriond: Electroweak Interactions and Unified Theories, Les Arcs, France, 15-22 March 2003High Energy Physics - Phenomenologytext