Astrophysical implications of the neutrino rest mass. I. The universe

Recent measurements of the spectrum of tritium decay electrons in the USSR suggest that electronic neutrinos may have a rest energy m/sub ν/c2approx. =30 eV. Primordial neutrinos would then make a major contribution to the mean density of matter in the universe, enough for the universe to be closed. If future reactor and accelerator experiments should reveal that muonic and tau neutrinos have a mass of the same order, then one would infer an age of less than 1010 yr for the Friedmann universe, contrary to the age observed for the oldest stars in the Galaxy. The contradiction can be removed by introducing the cosmological constant Λ. Conversely, measuring the rest mass of all neutrino species as well as the age of the universe would afford a unique opportunity to evaluate Λ