Model-Independent Signatures of New Physics in non-Gaussianity
  We compute the model-independent contributions to the primordial bispectrum and trispectrum in de Sitter space due to high-energy physics. We do this by coupling a light inflaton to an auxiliary heavy field, and then evaluating correlation functions in the Schwinger-Keldysh "in-in" formalism. The high-energy physics produces corrections parametrized by $H/M$ where $H$ is the scale of inflation and $M$ is the mass of the heavy field. The bispectrum peaks near the elongated shape, but otherwise contains no features. The trispectrum receives no corrections at order $H/M$. 
Mark G. Jackson, Koenraad Schalm
hep-th astro-ph.CO