2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45677The existence of a light singlet fermion mixed with the electron neutrino is hinted by the simultaneous explanation of various neutrino anomalies. We show that supersymmetry can provide a natural framework for the existence and the desired properties of such a fermion. Quasi Goldstone fermions (QGF) of spontaneously broken global symmetries like the Peccei-Quinn symmetry or lepton number can mix properly with the neutrinos provided the presence of the R-parity breaking term $\e LH_2$. The lightness of QGF can be a consequence of non-minimal Kähler potentials like that of no-scale supergravity. In order to keep R-parity, such a sterile component has to be placed in a new singlet superfield with no vacuum expectation value. In the context of the standard seesaw mechanism the lightness of such a singlet can be understood by imposing a $R$-symmetry.12 pages, Latex, 1 figure included (Talk presented at the workshop Valencia 95)High Energy Physics - Phenomenologytext