Finsler geometric perspective on the bulk flow in the universe
  Astronomical observations showed that there may exist a bulk flow with
peculiar velocities in the universe, which contradicts with the (\Lambda)CDM
model. The bulk flow reveals that the observational universe is anisotropic at
large scales. In fact, a more reliable observation on the anisotropy of
spacetime comes from the CMB power spectra. The WMAP and Planck satellites both
show that there is a hemispherical power asymmetry at large-angular scales. In
this paper, we propose a "wind" scenario to the bulk flow (or the anisotropy of
spacetime). Under the influence of the "wind", the spacetime metric could
become a Finsler structure. By resolving the null geodesic equation, we obtain
the modified luminosity distance, which has a dipolar form at the leading
order. Thus, the "wind" describes well the bulk flow. In addition, we perform a
least-(\chi^2) fit to the data of type Ia supernovae (SNe Ia) in the Union2.1
compilation. The peculiar velocity of the bulk flow has an upper limit
(v_{bulk}\lesssim 4000 \rm{km/s}), which is compatible with all the existing
observational values.
