On the possibility for constraining cosmic topology from the celestial
  distribution of astronomical objects
  We present a method to constrain cosmic topology from the distribution of
astronomical objects projected on the celestial sphere. This is an extension of
the 3D method introduced in Fujii & Yoshii (2011) that is to search for a pair
of pairs of observed objects (quadruplet) linked by a holonomy, i.e., the
method we present here is to search for a pair of celestial sphere $n$-tuplets
for $n \geq 3$. We find, however, that this method is impractical to apply in
realistic situations due to the small signal to noise ratio. We conclude
therefore that it is unrealistic to constrain the topology of the Universe from
the celestial distribution, and the 3D catalogs are necessary for the purpose.
