Holographic Non-Gaussianity

TL;DR

This paper develops a holographic approach to compute the non-Gaussianity of primordial cosmological perturbations, deriving a formula for the bispectrum from a dual quantum field theory, revealing a universal equilateral form.

Contribution

It introduces a holographic formula linking cosmological bispectrum to a dual QFT, enabling perturbative calculations for non-geometric early universe phases.

Findings

Primordial bispectrum is of equilateral shape with f_nl^eq=5/36 for certain models.

Holographic formula for three-point stress-energy tensor correlator derived.

Method allows computation of non-Gaussianity from holographic duals in inflation.

Abstract

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.