The statistically anisotropic curvature perturbation generated by
  f(\phi)^2 F^2
  The inflaton might be coupled to a gauge field through a term f^2(\phi)
F_\mu\nu F^\mu\nu. If f \propto a^{-2} where a(t) is the scale factor, the
perturbation \delta W of the gauge field generates a potentially observable
statistically anisotropic contribution to the primordial curvature perturbation
during slow-roll inflation. The spectrum and bispectrum of this contribution
have been calculated using the in-in formalism of quantum field theory. We give
a simpler and more complete calculation using only the classical perturbations.
The results suggest that either the entire curvature perturbation \zeta (both
the statistically isotropic and anisotropic parts) is generated during
slow-roll inflation, or else it is generated afterwards.
