Topology beyond the horizon: how far can it be probed?
  The standard cosmological model does not determine the spatial topology of
the universe. This article revisits the signature of a non-trivial topology on
the properties of the cosmic microwave background anisotropies. We show that
the correlation function of the coefficients of the expansion of the
temperature and polarization anisotropies in spherical harmonics, encodes a
topological signature that can be used to distinguish a multi-connected space
from an infinite space on sizes larger than the last scattering surface. The
effect of the instrumental noise and of a galactic cut are estimated. We thus
establish boundaries for the size of the biggest torus dintinguisable with
temperature and polarization CMB data. We also describe the imprint of the
spatial topology on the 3-point function and on non-Gaussianity.
