Majorons: a simultaneous solution to the large and small scale dark matter problems

Abstract It is shown that the existence of majorons, which enable a heavy neutrino, 500 eV ≲ mνH ≲ 25 keV to decay into a light neutrino mνL ≲ 8 eV and a majoron, with lifetime 104 yr ≲ τνH ≲ 108 yr can solve both the large and small scale dark matter problems. For a primordial “Zeldovich” spectrum of fluctuations the limits are m v H ≲ 550 eV and τ v H > 107 to 108 yr (the ranges mνH ≲ eV and τνH ≳ 108 yr are allowed by the model but galaxy formation becomes problematic). The large scale dark matter problem is how to achieve the critical density as implied by inflation, the small scale problems deal with the halos of galaxies and galaxy formation and perturbation growth. The heavy neutrino…