COLD PLUS HOT DARK-MATTER

The Cold + Hot Dark Matter (CHDM) model appears to require about 5 eV of neutrino mass in order to produce early enough galaxy formation. Re cent experimental data suggests that this neutrino mass may be divided between two species of neutrinos, each with mass of about 2.4 eV. Her e we consider the consequences of such neutrino masses for cosmologica l models for the formation of galaxies and large scale structure in th e universe, which are spatially flat and in which most of the dark mat ter is cold. The linear calculations and the new N-body simulation tha t we report here indicate that an Omega = 1 CHDM cosmological model wi th two neutrinos each of mass approximate to 2.4 eV (we will call this model C nu(2)DM) agrees remarkably well with all available observatio ns. However, we find that this is true only if the Hubble parameter H- 0 approximate to 50 km s(-1) Mpc(-1). We also consider Cold Dark Matte r (CDM) models with a cosmological constant Lambda and show that evide nce for hot dark matter raises serious difficulties for low-Omega ACDM models.