Operator product expansion of inflationary correlators and conformal symmetry of de Sitter

Kehagias, A; Riotto, A

dc.contributor.author	Kehagias, A	en
dc.contributor.author	Riotto, A	en
dc.date.accessioned	2014-03-01T02:11:50Z
dc.date.available	2014-03-01T02:11:50Z
dc.date.issued	2012	en
dc.identifier.issn	05503213	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/29958
dc.subject	Conformal field theory	en
dc.subject	Curvaton	en
dc.subject	Inflation	en
dc.subject	Non-Gaussianities	en
dc.subject	Operator product expansion	en
dc.subject	Suyama-Yamaguchi inequality	en
dc.title	Operator product expansion of inflationary correlators and conformal symmetry of de Sitter	en
heal.type	journalArticle	en
heal.identifier.primary	10.1016/j.nuclphysb.2012.07.004	en
heal.identifier.secondary	http://dx.doi.org/10.1016/j.nuclphysb.2012.07.004	en
heal.publicationDate	2012	en
heal.abstract	We study the multifield inflationary models where the cosmological perturbation is sourced by light scalar fields other than the inflaton. The corresponding perturbations are both scale invariant and special conformally invariant. We exploit the operator product expansion technique of conformal field theories to study the inflationary correlators enjoying the symmetries present during the de Sitter epoch. The operator product expansion is particularly powerful in characterizing inflationary correlation functions in two observationally interesting limits, the squeezed limit of the three-point correlator and the collapsed limit of the four-point correlator. Despite the fact that the shape of the four-point correlators is not fixed by the symmetries of de Sitter, its exact shape can be found in the collapsed limit making use of the operator product expansion. By employing the fact that conformal invariance imposes the two-point cross-correlations of the light fields to vanish unless the fields have the same conformal weights, we are able to show that the Suyama-Yamaguchi inequality relating the coefficients fNL of the bispectrum in the squeezed limit and τNL of the trispectrum in the collapsed limit also holds when the light fields are intrinsically non-Gaussian. In fact, we show that the inequality is valid irrespectively of the conformal symmetry, being just a consequence of fundamental physical principles, such as the short-distance expansion of operator products. The observation of a strong violation of the inequality will then have profound implications for inflationary models as it will imply either that multifield inflation cannot be responsible for generating the observed fluctuations independently of the details of the model or that some new non-trivial degrees of freedom play a role during inflation. © 2012 Elsevier B.V.	en
heal.journalName	Nuclear Physics B	en
dc.identifier.doi	10.1016/j.nuclphysb.2012.07.004	en
dc.identifier.volume	864	en
dc.identifier.issue	3	en
dc.identifier.spage	492	en
dc.identifier.epage	529	en