The squeezed limit of the bispectrum in multi-field inflation
  We calculate the squeezed limit of the bispectrum produced by inflation with
multiple light fields. To achieve this we allow for different horizon exit
times for each mode and calculate the intrinsic field-space three-point
function in the squeezed limit using soft-limit techniques. We then use the
$\delta N$ formalism from the time the last mode exits the horizon to calculate
the bispectrum of the primordial curvature perturbation. We apply our results
to calculate the spectral index of the halo bias, $n_{\delta b}$, an important
observational probe of the squeezed limit of the primordial bispectrum and
compare our results with previous formulae. We give an example of a curvaton
model with $n_{\delta b} \sim {\cal O}(n_s-1)$ for which we find a 20%
correction to observable parameters for squeezings relevant to future
experiments. For completeness, we also calculate the squeezed limit of
three-point correlation functions involving gravitons for multiple field
models.
