Hierarchical fermion masses in SU(5)

Radiative masses are generated for the first and the second fermion families by exploiting the idea that their chirality is a symmetry of the 'low-energy' SU(3) x SU(2) x U(1) approximation of SU(5), broken only by including the effects of superheavy particles. With only 5's of Higgs coupled to fermions and getting a non-zero vacuum expectation value, we unavoidably get (i) msub(s) = msub(μ)/3 at the grand unification scale; (ii) the charm quark needing a direct mass as the third family; (iii) neutrino masses of size approx. <= (α/π)M2sub(W)/M. (orig.)