Symmetries and Loops in Inflation
  In this paper, we prove that the superhorizon conservation of the curvature perturbation zeta in single-field inflation holds as an operator statement. This implies that all zeta-correlators are time independent at all orders in the loop expansion. Our result follows directly from locality and diffeomorphism invariance of the underlying theory. We also explore the relationship between the conservation of zeta, the single-field consistency relation and the renormalization of composite operators. 
Valentin Assassi, Daniel Baumann, and Daniel Green
hep-th astro-ph.CO hep-ph