• DOI:10.1088/1475-7516/2011/04/030
• Corpus ID: 118417222

Moment transport equations for the primordial curvature perturbation

@article{Mulryne2011MomentTE,
  title={Moment transport equations for the primordial curvature perturbation},
  author={David J. Mulryne and D avid Seery and Daniel H. Wesley},
  journal={Journal of Cosmology and Astroparticle Physics},
  year={2011},
  volume={2011},
  pages={030-030}
}

• D. Mulryne, D. Seery, D. Wesley
• Published 18 August 2010
• Mathematics
• Journal of Cosmology and Astroparticle Physics

In 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 ζ 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(M3). 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 ~ 102 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.