Statistically anisotropic curvature perturbation generated during the   waterfall
  If the waterfall field of hybrid inflation couples to a U(1) gauge field, the waterfall can generate a statistically anisotropic contribution to the curvature perturbation. We investigate this possibility, generalising in several directions the seminal work of Yokoyama and Soda. The statistical anisotropy of the bispectrum could be detectable by PLANCK even if the statistical anisotropy of the spectrum is too small to detect. 
David H. Lyth and Mindaugas Karciauskas
astro-ph.CO hep-ph hep-th