2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54443After recalling a few basic concepts from cosmology and string theory, I will discuss the main ideas/assumptions underlying string cosmology and show how these lead to a two-parameter family of ``minimal" models. I will then explain how to compute, in terms of those parameters, the spectrum of scalar, tensor and electromagnetic perturbations, point at their ($T$ and $S$-type) duality symmetries, and mention their most relevant physical consequences.21p, latex, epsf, 3 figures in uuencoded fileHigh Energy Physics - Theorytext