An argument that the dark matter is axions
  An argument is presented that the dark matter is axions, at least in part. It
has three steps. First, axions behave differently from the other forms of cold
dark matter because they form a rethermalizing Bose-Einstein condensate (BEC).
Second, there is a tool to distinguish axion BEC from the other dark matter
candidates on the basis of observation, namely the study of the inner caustics
of galactic halos. Third, the observational evidence for caustic rings of dark
matter is consistent in every aspect with axion BEC, but not with the other
proposed forms of dark matter.
