Preferred axis in cosmology
  The foundation of modern cosmology relies on the so-called cosmological
principle which states an homogeneous and isotropic distribution of matter in
the universe on large scales. However, recent observations, such as the
temperature anisotropy of the cosmic microwave background (CMB) radiation, the
motion of galaxies in the universe, the polarization of quasars and the
acceleration of the cosmic expansion, indicate preferred directions in the sky.
If these directions have a cosmological origin, the cosmological principle
would be violated, and modern cosmology should be reconsidered. In this paper,
by considering the preferred axis in the CMB parity violation, we find that it
coincides with the preferred axes in CMB quadrupole and CMB octopole, and they
all align with the direction of the CMB kinematic dipole. In addition, the
preferred directions in the velocity flows, quasar alignment, anisotropy of the
cosmic acceleration, the handedness of spiral galaxies, and the angular
distribution of the fine-structure constant are also claimed to be aligned with
the CMB kinematic dipole. Since CMB dipole was confirmed to be caused by the
motion of our local group of galaxies relative to the reference frame of the
CMB, the coincidence of all these preferred directions hints that these
anomalies have a common origin, which is not cosmological or due to a
gravitational effect. The systematical or contaminative errors in observation
or in data analysis, which can be directly related to the motion of our local
group of galaxies, can play an important role in explaining the anomalies.
