2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/194143Future cosmological data may be sensitive to the effects of a finite sum of neutrino masses even as small as ~0.06 eV, the lower limit guaranteed by neutrino oscillation experiments. We show that a cosmological detection of neutrino mass at that level would improve by many orders of magnitude the existing limits on neutrino lifetime, and as a consequence on neutrino secret interactions with (quasi-)massless particles as in majoron models. On the other hand, neutrino decay may provide a way-out to explain a discrepancy <~ 0.1 eV between cosmic neutrino bounds and Lab data.5 pages, 1 eps figure; clarifications and references added, improved discussion, conclusions unchanged. Matches version published in PRLAstrophysicsHigh Energy Physics - Phenomenologytext