2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53263We review some recent developments in string theory, emphasizing the importance of vacuum instabilities, their relation to the density of states, and the role of space-time fermions in non-critical string theory. We also discuss the classical dynamics of two dimensional string theory.39 pagesHigh Energy Physics - Theorytext