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Moment transport equations for the primordial curvature perturbation
journal contribution
posted on 2023-06-08, 06:20 authored by David J Mulryne, David SeeryDavid Seery, Daniel WesleyIn a recent publication, we proposed that inflationary perturbation theory can be reformulated in terms of a probability transport equation, whose moments determine the correlation properties of the primordial curvature perturbation. In this paper we generalize this formulation to an arbitrary number of fields. We deduce ordinary differential equations for the evolution of the moments of zeta on superhorizon scales, which can be used to obtain an evolution equation for the dimensionless bispectrum, fNL. Our equations are covariant in field space and allow identification of the source terms responsible for evolution of fNL. In a model with M scalar fields, the number of numerical integrations required to obtain solutions of these equations scales like O(M^3). The performance of the moment transport algorithm means that numerical calculations with M >> 1 fields are straightforward. We illustrate this performance with a numerical calculation of fNL in Nflation models containing M ~ 10^2 fields, finding agreement with existing analytic calculations. We comment briefly on extensions of the method beyond the slow-roll approximation, or to calculate higher order parameters such as gNL.
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Publication status
- Published
Journal
Journal of Cosmology and Astroparticle PhysicsExternal DOI
Issue
04Volume
2011Page range
030Pages
23.0Department affiliated with
- Physics and Astronomy Publications
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Author list in alphabetical order.Full text available
- No
Peer reviewed?
- Yes
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2012-02-06Usage metrics
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