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Spatial curvature at the sound horizon

Accepted version
Peer-reviewed

Type

Article

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Authors

Avis, G 
Supeł, J 

Abstract

The effect of spatial curvature on primordial perturbations is controlled by  ΩK,0/cs2 , where  ΩK,0  is today's fractional density of spatial curvature and  cs  is the speed of sound during inflation. Here we study these effects in the limit  cs≪ 1 . First, we show that the standard cosmological soft theorems in flat universes are violated in curved universes and the soft limits of correlators can have non-universal contributions even in single-clock inflation. This is a consequence of the fact that, in the presence of spatial curvature, there is a gap between the spectrum of residual diffeomorphisms and that of physical modes. Second, there are curvature corrections to primordial correlators, which are not scale invariant. We provide explicit formulae for these corrections to the power spectrum and the bispectrum to linear order in curvature in single-clock inflation. We show that the large-scale CMB anisotropies could provide interesting new constraints on these curvature effects, and therefore on  ΩK,0/cs2 , but it is necessary to go beyond our linear-order treatment.

Description

Keywords

non-gaussianity, cosmological perturbation theory, inflation

Journal Title

Journal of Cosmology and Astroparticle Physics

Conference Name

Journal ISSN

1475-7516
1475-7516

Volume Title

2020

Publisher

IOP Publishing

Rights

All rights reserved
Sponsorship
Science and Technology Facilities Council (ST/P000673/1)