Non-locality in Quantum Field Theory due to General Relativity
  We show that General Relativity coupled to a quantum field theory generically
leads to non-local effects in the matter sector. These non-local effects can be
described by non-local higher dimensional operators which remarkably have an
approximate shift symmetry. When applied to inflationary models, our results
imply that small non-Gaussianities are a generic feature of models based on
General Relativity coupled to matter fields. However, these effects are too
small to be observable in the Cosmic Microwave Background.
