Non-local bispectra from super cosmic variance
  We present examples of non-Gaussian statistics that can induce bispectra
matching local and non-local (including equilateral) templates in biased
sub-volumes. We find cases where the biasing from coupling to long wavelength
modes affects only the power spectrum, only the bispectrum or both. Our results
suggest that ruling out multi-field scenarios is quite difficult: some
measurements of the scalar correlations, including the shape of the bispectrum,
can be consistent with single-clock predictions even when cosmic variance from
super-horizon modes is at work. Furthermore, if observations of the density
perturbations rule out single-clock inflation, we will face a serious cosmic
variance obstacle in drawing any further conclusions about the particle physics
origin of the scalar fluctuations.
