Impact of transforming to Conformal Fermi Coordinates on Quasi-Single
  Field Non-Gaussianity
  In general relativity predictions for observable quantities can be expressed
in a coordinate independent way. Nonetheless it may be inconvenient to do so.
Using a particular frame may be the easiest way to connect theoretical
predictions to measurable quantities. For the cosmological curvature bispectrum
such frame is described by the Conformal Fermi Coordinates. In single field
inflation it was shown that going to this frame cancels the squeezed limit of
the density perturbation bispectrum calculated in Global Coordinates. We
explore this issue in quasi single field inflation when the curvaton mass and
the curvaton-inflaton mixing are small. In this case, the contribution to the
bispectrum from the coordinate transformation to Conformal Fermi Coordinates is
of the same order as that from the inflaton-curvaton interaction term but does
not cancel it.
