2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/50266Fate of branes in external fields is reviewed. Spontaneous creation of the Brane World in $AdS_{5}$ with external field is described. The resulting Brane World consists of a flat 4d spatially finite expanding Universe and curved expanding "regulator" branes. All branes have a positive tension.13 pages, contribution to the Proceedings of E.S.Fradkin Memorial Conference, Moscow, 2000High Energy Physics - Theorytext