Inflationary perturbation theory is geometrical optics in phase space

Seery, David, Mulryne, David, Frazer, Jonathan and Ribeiro, Raquel (2012) Inflationary perturbation theory is geometrical optics in phase space. Journal of Cosmology and Astroparticle Physics, 2012 (9). 010. ISSN 1475-7516

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Abstract

A pressing problem in comparing inflationary models with observation is the accurate calculation of correlation functions. One approach is to evolve them using ordinary differential equations ("transport equations"), analogous to the Schwinger-Dyson hierarchy of in-out quantum field theory. We extend this approach to the complete set of momentum space correlation functions. A formal solution can be obtained using raytracing techniques adapted from geometrical optics. We reformulate inflationary perturbation theory in this language, and show that raytracing reproduces the familiar "δN" Taylor expansion. Our method produces ordinary differential equations which allow the Taylor coefficients to be computed efficiently. We use raytracing methods to express the gauge transformation between field fluctuations and the curvature perturbation, ζ, in geometrical terms. Using these results we give a compact expression for the nonlinear gauge-transform part of fNL in terms of the principal curvatures of uniform energy-density hypersurfaces in field space.

Item Type: Article
Keywords: cosmological perturbation theory; inflation
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy > QB0980 Cosmogony. Cosmology
Depositing User: David Seery
Date Deposited: 25 Sep 2012 10:42
Last Modified: 25 Sep 2012 10:42
URI: http://sro.sussex.ac.uk/id/eprint/40583
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