Abstract
AbstractWe present the holographic predictions for cosmological 3-point correlators, involving both scalar and tensor modes, for a universe which started in a non-geometric holographic phase. Holographic formulae relate the cosmological 3-point functions to stress tensor correlation functions of a holographically dual three-dimensional non-gravitational QFT. We compute these correlators at 1-loop order for a theory containing massless scalars, fermions and gauge fields, and present an extensive analysis of the constraints due to Ward identities showing that they uniquely determine the correlators up to a few constants. We define shapes for all cosmological bispectra and compare the holographic shapes to the slow-roll ones, finding that some are distinguishable while others, perhaps surprisingly, are not. In particular, for three gravitons, we are able to recover the slow-roll shapes exactly.
Highlights
In a recent series of papers [1,2,3,4,5,6] we put forward a holographic framework for inflationary cosmology and discussed a novel class of models describing a universe that started in a nongeometric phase, which is described holographically via a large-N three-dimensional QFT
In this paper we computed the complete set of bispectra for a class of holographic models of the very early universe based
The field content of the dual theory includes gauge fields, massless fermions, massless minimal and conformal scalars and the parameters that can appear in the results are the number of species for each type of field
Summary
In a recent series of papers [1,2,3,4,5,6] we put forward a holographic framework for inflationary cosmology and discussed a novel class of models describing a universe that started in a nongeometric phase, which is described holographically via a large-N three-dimensional QFT. We worked out the holographic dictionary for non-Gaussianities involving tensors in [6], and in this paper we compute the relevant QFT correlation functions. The 3-point functions involving only tensors are determined by the 3-point functions of conformal scalars and fermions, and, as in the discussion of [7], they agree exactly with slow-roll inflation if the field content of the dual QFT is appropriately chosen. Several technical results are presented in four appendices: in appendix A we summarise our notation and conventions for the helicity tensors, in appendix B we present three different methods for evaluating the relevant diagrams, in appendix C we show that ghosts and gauge fixing terms do not contribute in correlators of the stress tensor and in appendix D we present the conformal and diffeomorphicm Ward identities
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