Holographic Non-Gaussianity
  We investigate the non-Gaussianity of primordial cosmological perturbations
within our recently proposed holographic description of inflationary universes.
We derive a holographic formula that determines the bispectrum of cosmological
curvature perturbations in terms of correlation functions of a holographically
dual three-dimensional non-gravitational quantum field theory (QFT). This
allows us to compute the primordial bispectrum for a universe which started in
a non-geometric holographic phase, using perturbative QFT calculations.
Strikingly, for a class of models specified by a three-dimensional
super-renormalisable QFT, the primordial bispectrum is of exactly the
factorisable equilateral form with f_nl^eq=5/36, irrespective of the details of
the dual QFT. A by-product of this investigation is a holographic formula for
the three-point function of the trace of the stress-energy tensor along general
holographic RG flows, which should have applications outside the remit of this
work.
