The problem of neutrino masses in extensions of the standard model (Q2783547)

The author reviews the problem of neutrino masses and mixing in the context of grand unified theories. Sections 2-4 of the review contain a summary of the present experimental status and future perspectives about neutrinos show the two basic mechanisms to provide an explanation of the large atmospheric mixing and present explicit grand unified models which realize these two possibilities. Then the author reviews in detail the various severe problems which plague minimal grand unified theories models and which force to investigate the possibility of constructing more elaborate but realistic models. In the section 5 an example of a quasirealistic SUSY SU(5) which, by exploiting the crucial presence of an Abelian flavor symmetry, is constructed which is not plagued by the need for large amounts of fine tunings and leads to an acceptable phenomenology with respect to coupling unification, fermion masses, mixings and bounds from proton decay.