  Massive neutrinos have a detectable effect on cosmological structure
formation, in particular on the large-scale distribution of galaxies. Adding
Hot Dark Matter to the now-standard Lambda CDM model leads to a worse fit to
large-scale structure and CMB anisotropy data. This results in a limit on the
mass of the most massive neutrino of 4 eV, assuming a power-law primordial
power spectrum.
