Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2016, Tutor: Joan Solà PeracaulaThe possibility of a slow cosmic evolution of fundamental \constants" of Nature has been discussed for a long time without being consolidated; recently, however, more and more experiments are arising whose results seem to support this idea. Apart from that, in an expanding universe the vacuum energy density p is expected to be a time-evolving parameter rather than the rigid one proposed in the standard ACDM model; in fact, quantum feld theory in curved space time suggests a slow evolution determined by the expansion rate of the universe H. In this work, we will try to obtain and develop some cosmological models with such a a dynamical vacuum energy density, and at the same time we will check whether they can provide an explanation for the alleged slow time variation of the fundamental constants