We analyze both chirality-changing and chirality-preserving transitions of Dirac–Majorana neutrinos. In vacuum, the first ones are suppressed with respect to the others due to helicity conservation and the interactions with a ("normal") medium practically does not affect the expressions of the probabilities for these transitions, even if the amplitudes of oscillations change slightly. For usual situations involving relativistic neutrinos we find no resonant enhancement for all flavor-conserving transitions. However, for very light neutrinos propagating in superdense media, the pattern of oscillations [Formula: see text] is dramatically altered with respect to the vacuum case, the transition probability practically vanishing. An application of this result is envisaged.
Unveiling dipolar spectral regimes of large dielectric Mie spheres from helicity conservation
