Holography for Cosmology
  We propose a holographic description of four-dimensional single-scalar
inflationary universes, and show how cosmological observables, such as the
primordial power spectrum, are encoded in the correlation functions of a
three-dimensional QFT. The holographic description correctly reproduces
standard inflationary predictions in the limit where a perturbative
quantization of fluctuations is justified. In the opposite limit, wherein
gravity is strongly coupled at early times, we propose a holographic
description in terms of perturbative large N QFT. Initiating a holographic
phenomenological approach, we show that models containing only two parameters,
N and a dimensionful coupling constant, are capable of satisfying the current
observational constraints.
