Holography for inflation using conformal perturbation theory
  We provide a precise and quantitative holographic description of a class of
inflationary slow-roll models. The dual QFT is a deformation of a
three-dimensional CFT by a nearly marginal operator, which, in the models we
consider, generates an RG flow to a nearby IR fixed point. These models
describe hilltop inflation, where the inflaton rolls from a local maximum of
the potential in the infinite past (corresponding to the IR fixed point of the
dual QFT) to reach a nearby local minimum in the infinite future (corresponding
to the UV of the dual QFT). Through purely holographic means, we compute the
spectra and bispectra of scalar and tensor cosmological perturbations. The QFT
correlators to which these observables map holographically may be calculated
using conformal perturbation theory, even when the dual QFT is strongly
coupled. Both the spectra and the bispectra may be expressed this way in terms
of CFT correlators that are fixed, up to a few constants, by conformal
invariance. The form of slow-roll inflationary correlators is thus determined
by the perturbative breaking of the de Sitter isometries away from the fixed
point. Setting the constants to their values obtained by AdS/CFT at the fixed
point, we find exact agreement with known expressions for the slow-roll power
spectra and non-Gaussianities.
