Neutrino masses: model building

We review various models of flavour symmetries that have been proposed in order to explain the solar and atmospheric neutrino deficits. Although there is a wide range of solutions within different frameworks, it is possible to identify some common characteristics which, in view of the expected neutrino data, may be used in order to constraint or even exclude certain classes of models. We discussed different models of neutrino mass textures, in the light of the atmospheric and solar neutrino data. There have been many different proposals in the literature, on how the viable phenomenological textures may arise in models with flavour and GUT symmetries. Here, we focus in identifying common characteristics of the various theories, in a way that the new data can constrain or even exclude whole classes of models. For instance, a generic feature of models based on Abelian flavour symmetries is that, in the absence of cancellations, most models predict a small mixing angle for the solar neutrino deficit and hierarchical neutrino masses. On the other hand, non-Abelian flavour symmetries can generate more naturally degenerate neutrinos with bimaximal mixing. If the future data can tell us which solution we have for the solar neutrinos, a dear indication of the flavour structure of the underlying theory is obtained. (14 refs).