THE FORMATION OF COSMIC STRUCTURE WITH A 17 KEV NEUTRINO

Adding a 17 keV neutrino with a lifetime of approximately 1 yr can explain the puzzling large-scale structure observed in the galaxy distribution which is difficult to understand in the "standard" cold dark matter model with the adiabatic scale invariant density fluctuations predicted by inflation. Decay times greater-than-or-similar-to 10 yr are incompatible with microwave background anisotropy limits and galaxy clustering observations.