http://arxiv.org/abs/1503.04205 advances a new hypothesis. There are dark matter analogues of quarks and gluons allowing the dark-quarks to form dark-neutrons. The dark strong force is stronger than the usual strong force causing the dark neutrons to be more strongly bound. (Actually this paper's setup is not the exact analogue of quarks, mathematically, but close enough for my present purposes.) The interesting thing about this class of hypotheses is, the dark quarks actually would be charged particles and hence highly visible with ordinary photons, i.e. naively not "dark" at all. However, due to the unbreakable binding into dark-neutrons, which are uncharged, they effectively are invisible EXCEPT to very high energy photons, or in the early universe when it was very hot, there presumably were charged dark particles too. This allows new phenomena to happen that old-style dark matter would not have permitted, giving them more freedom to fit their baloney to observations. This kind of dark matter also ought to be observable even today in interactions with high energy particles. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)