\delta N versus covariant perturbative approach to non-Gaussianity   outside the horizon in multifield inflation
  We compute the super-Hubble evolution of non-Gaussianity of primordial curvature perturbations in two-field inflation models by employing two formalisms: delta N and covariant formalisms. Although two formalisms treat the evolution of fluctuations radically different, we show that the formulas of f_{NL} parameter agree quantitatively with each other within 1 % accuracy. We analytically find that the amplitude of f_{NL} decays no faster than a^{-3} as the inflationary trajectory reaches to the adiabatic limit for generic potentials. 
Yuki Watanabe (ASC, LMU Munich)
astro-ph.CO gr-qc hep-ph hep-th