Prospects for constraining the shape of non-Gaussianity with the
  scale-dependent bias
  We consider whether the non-Gaussian scale-dependent halo bias can be used
not only to constrain the local form of non-Gaussianity but also to distinguish
among different shapes. In particular, we ask whether it can constrain the
behavior of the primordial three-point function in the squeezed limit where one
of the momenta is much smaller than the other two. This is potentially
interesting since the observation of a three-point function with a squeezed
limit that does not go like the local nor equilateral templates would be a
signal of non-trivial dynamics during inflation. To this end we use the
quasi-single field inflation model of Chen and Wang as a representative
two-parameter model, where one parameter governs the amplitude of
non-Gaussianity and the other the shape. We also perform a model-independent
analysis by parametrizing the scale-dependent bias as a power-law on large
scales, where the power is to be constrained from observations. We find that
proposed large-scale structure surveys (with characteristics similar to the
dark energy task force stage IV surveys) have the potential to distinguish
among the squeezed limit behavior of different bispectrum shapes for a wide
range of fiducial model parameters. Thus the halo bias can help discriminate
between different models of inflation.
