Conformal invariance of curvature perturbation
  We show that in the single component situation all perturbation variables in the comoving gauge are conformally invariant to all perturbation orders. Generally we identify a special time slicing, the uniform-conformal transformation slicing, where all perturbations are again conformally invariant to all perturbation orders. We apply this result to the delta N formalism, and show its conformal invariance. 
Jinn-Ouk Gong, Jai-chan Hwang, Wan Il Park, Misao Sasaki and Yong-Seon   Song
gr-qc astro-ph.CO hep-ph hep-th