Relativistic Effect in Galaxy Clustering
  The general relativistic description of galaxy clustering provides a complete
and unified treatment of all the effects in galaxy clustering such as the
redshift-space distortion, gravitational lensing, Sachs-Wolfe effects, and
their relativistic effects. In particular, the relativistic description
resolves the gauge issues in the standard Newtonian description of galaxy
clustering by providing the gauge-invariant expression for the observed galaxy
number density. The relativistic effect in galaxy clustering is significant on
large scales, in which dark energy models or alternative theories of modified
gravity deviate from general relativity. In this paper, we review the
relativistic effect in galaxy clustering by providing a pedagogical derivation
of the relativistic formula and by computing the observed galaxy two-point
statistics. The relativistic description of galaxy clustering is an essential
tool for testing general relativity and probing the early Universe on large
scales in the era of precision cosmology.
