Primordial curvature perturbation during and at the end of multi-field   inflation
  We study the generation of the primordial curvature perturbation in multi-field inflation. Considering both the evolution of the perturbation during inflation and the effects generated at the end of inflation, we present a general formula for the curvature perturbation. We provide the analytic expressions of the power spectrum, spectral tilt and non-Gaussianity for the separable potentials of two inflaton scalars, and apply them to some specific models. 
Ki-Young Choi, Soo A Kim, Bumseok Kyae
astro-ph.CO hep-ph