Observational signatures of holographic models of inflation

TL;DR

This paper explores holographic models of inflation where the early universe is described by a dual quantum field theory, predicting universal features in primordial fluctuations that can be tested by observations.

Contribution

It demonstrates that a class of holographic inflation models predicts universal observational signatures independent of specific QFT details.

Findings

Nearly scale-invariant primordial fluctuation spectrum

Scalar spectral index with specific running alpha_s

Equilateral form of three-point scalar function with fixed f_nl^eq

Abstract

We discuss the phenomenology of recently proposed holographic models of inflation, in which the very early universe is non-geometric and is described by a dual three-dimensional quantum field theory (QFT). We analyze models determined by a specific class of dual QFTs and show that they have the following universal properties: (i) they have a nearly scale invariant spectrum of small amplitude primordial fluctuations, (ii) the scalar spectral index runs as alpha_s = -(n_s-1), (iii) the three-point function of primordial scalar perturbations is of exactly the factorizable equilateral form with f_nl^eq=5/36. These properties hold irrespective of the details (e.g. field content, strength of interactions, etc.) of the dual QFT within the class of theories we analyze. The ratio of tensors-to-scalars is determined by the field content of the dual QFT and does not satisfy the slow-roll consistency relations. Observations from the Planck satellite should be able to confirm or exclude these models.