2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/40339These lectures review certain topological defects and aspects of their cosmology. Unconventional material includes brief descriptions of electroweak defects, the structure of domain walls in non-Abelian theories, and the spectrum of magnetic monopoles in SU(5) Grand Unified theory.34 pages; lectures at the 2000 summer school in cosmology at ICTP, Trieste; minor correction in domain wall sectionHigh Energy Physics - PhenomenologyAstrophysicsHigh Energy Physics - Theorytext