Cosmological Lower Bound on Heavy-Neutrino Masses

Abstract

The present cosmic mass density of possible stable neutral heavy leptons is calculated in a standard cosmological model. In order for this density not to exceed the upper limit of 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}29}$ g/${\mathrm{cm}}^{3}$, the lepton mass would have to be greater than a lower bound of the order of 2 GeV.