Statistical Anisotropy in Inflationary Models with Many Vector Fields
  and/or Prolonged Anisotropic Expansion
  We study the most general contributions due to scalar field perturbations,
vector field perturbations, and anisotropic expansion to the generation of
statistical anisotropy in the primordial curvature perturbation \zeta. Such a
study is done using the \delta N formalism where only linear terms are
considered. Here, we consider two specific cases that lead to determine the
power spectrum P_\zeta(k) of the primordial curvature perturbation. In the
first one, we consider the possibility that the n-point correlators of the
field perturbations in real space are invariant under rotations in space
(statistical isotropy); as a result, we obtain as many levels of statistical
anisotropy as vector fields present and, therefore, several preferred
directions. The second possibility arises when we consider anisotropic
expansion, which leads us to obtain I+a additional contributions to the
generation of statistical anisotropy of \zeta compared with the former case,
being I and a the number of scalar and vector fields involved respectively.
