Cosmological 3-point correlators from holography

TL;DR

The paper develops a holographic framework to map primordial cosmological non-Gaussianities to stress-energy correlators of a dual 3D QFT via the domain-wall/cosmology correspondence. It introduces response-function methods to compute 3-point functions in cosmology and derives holographic formulae expressing them in terms of the dual QFT's 2- and 3-point functions, including semi-local terms. For Einstein gravity, tensor-containing bispectra are determined by positive-helicity data with universal momentum ratios. The results extend to general holographic RG flows and asymptotically power-law domain-walls, enabling applications beyond standard slow-roll models.

Abstract

We investigate the non-Gaussianity of primordial cosmological perturbations using holographic methods. In particular, we derive holographic formulae that relate all cosmological 3-point correlation functions, including both scalar and tensor perturbations, to stress-energy correlation functions of a holographically dual three-dimensional quantum field theory. These results apply to general single scalar inflationary universes that at late times approach either de Sitter spacetime or accelerating power-law cosmologies. We further show that in Einstein gravity all 3-point functions involving tensors can be obtained from correlators containing only positive helicity gravitons, with the ratios of these to the correlators involving one negative helicity graviton being given by universal functions of momenta, irrespectively of the potential of the scalar field. As a by-product of this investigation, we obtain holographic formulae for the full 3-point function of the stress-energy tensor along general holographic RG flows. These results should have applications in a wider holographic context.