Schwinger-Keldysh mechanism in extended quasi single field inflation
  We study an extension of quasi-single field model of inflation containing
multiple semi-heavy isocurvaton fields using the Schwinger-Keldysh mechanism.
We calculate the amplitudes and the shapes of the bispectrum and the
trispectrum. We show that the diagrammatic approach associated with the
Schwinger-Keldysh mechanism simplifies the analysis considerably compared to
standard in-in formalism. This method is helpful to study the spectroscopy of
masses and couplings of light and semi-heavy fields during inflation.
