Dark matter in ghost-free bigravity theory: From a galaxy scale to the
  universe
  We study the origin of dark matter based on the ghost-free bigravity theory
with twin matter fluids. The present cosmic acceleration can be explained by
the existence of graviton mass, while dark matter is required in several
cosmological situations [the galactic missing mass, the cosmic structure
formation and the standard big-bang scenario (the cosmological nucleosynthesis
vs the CMB observation)]. Assuming that the Compton wavelength of the massive
graviton is shorter than a galactic scale, we show the bigravity theory can
explain dark matter by twin matter fluid as well as the cosmic acceleration by
tuning appropriate coupling constants.
