Goldberger-Wise variations: Stabilizing brane models with a bulk scalar

Models with compact extra–dimensions need the volume of the extra space to be stabilized. This is a typical problem of string–theoretical constructions, in which the existence of a mass term for moduli is vital for the viability of the models. The inevitability of 9 or 10 spatial dimensions in string theory provides one of the main motivations for the recent interest about extra–dimensions, although many scenarios that are not necessarily linked to string theory have also been envisaged. Among these, the one proposed by Randall and Sundrum [1] has been object of intense study. One of the (many) features that make the scenario so interesting is the presence of a single extra–dimension, that allows for a detailed – and not too complicated – analysis of the model and of its possible modifications.