Numerical evaluation of the bispectrum in multiple field inflation

Dias, Mafalda, Frazer, Jonathan, Mulryne, David J and Seery, David (2016) Numerical evaluation of the bispectrum in multiple field inflation. Journal of Cosmology and Astroparticle Physics, 2016 (12). 033. ISSN 1475-7516

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We present a complete framework for numerical calculation of the power spectrum and bispectrum in canonical inflation with an arbitrary number of light or heavy fields. Our method includes all relevant effects at tree-level in the loop expansion, including (i) interference between growing and decaying modes near horizon exit; (ii) correlation and coupling between species near horizon exit and on superhorizon scales; (iii) contributions from mass terms; and (iv) all contributions from coupling to gravity. We track the evolution of each correlation function from the vacuum state through horizon exit and the superhorizon regime, with no need to match quantum and classical parts of the calculation; when integrated, our approach corresponds exactly with the tree-level Schwinger or 'in-in' formulation of quantum field theory. In this paper we give the equations necessary to evolve all two- and three-point correlation functions together with suitable initial conditions. The final formalism is suitable to compute the amplitude, shape, and scale dependence of the bispectrum in models with |fNL| of order unity or less, which are a target for future galaxy surveys such as Euclid, DESI and LSST. As an illustration we apply our framework to a number of examples, obtaining quantitatively accurate predictions for their bispectra for the first time. Two accompanying reports describe publicly-available software packages that implement the method.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Astronomy Centre
Subjects: Q Science > QB Astronomy > QB0980 Cosmogony. Cosmology
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Depositing User: David Seery
Date Deposited: 03 Jan 2017 11:04
Last Modified: 20 Dec 2017 02:00

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Project NameSussex Project NumberFunderFunder Ref
Precisions tests of the inflationary scenarioG0918EUROPEAN UNION308082
Philip Leverhulme Prize - David SeeryG0810LEVERHULME TRUSTPLP-2011-157