Z3 dark matter and two-loop neutrino mass

Dark matter and neutrino mass are two of the most important issues to be understood in particle physics and astrophysics. Dark matter is universally assumed to be distinguished from ordinary matter by an odd-even parity, i.e. the discrete symmetry Z2, but that is not based on any fundamental principle. As an alternative and foil, a simple model of Z3 dark matter is proposed and shown to be natural for understanding the smallness of neutrino mass as a two-loop radiative effect.