A Class of Three-Loop Models with Neutrino Mass and Dark Matter
  We study a class of three-loop models for neutrino mass in which dark matter plays a key role in enabling the mass diagram. The simplest models in this class have Majorana dark matter and include the proposal of Krauss, Nasri and Trodden; we identify the remaining related models, including the viable colored variants. The next-to-simplest models use either more multiplets and/or a slight modification of the loop-diagram, and predict inert N-tuplet scalar dark matter. 
Chian-Shu Chen, Kristian L. McDonald and Salah Nasri
hep-ph