Towards general patterns of features in multi-field inflation
  We investigate the consequences of general curved trajectories in multi-field
inflation. After setting up a completely general formalism using the mass
basis, which naturally accommodates the notion of light and heavy modes, we
study in detail the simple case of two successive turns in two-field system. We
find the power spectrum of the curvature perturbation receives corrections that
exhibit oscillatory features sinusoidal in the logarithm of the comoving
wavenumber without slow-roll suppression. We show that this is because of the
resonance of the heavy modes inside and outside the mass horizon.
