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de Sitter limit of inflation and nonlinear perturbation theory
We study the fourth order action of the comoving curvature perturbation in an
inflationary universe in order to understand more systematically the de Sitter
limit in nonlinear cosmological perturbation theory. We derive the action of
the curvature perturbation to fourth order in the comoving gauge, and show that
it vanishes sufficiently fast in the de Sitter limit. By studying the de Sitter
limit, we then extrapolate to the n'th order action of the comoving curvature
perturbation and discuss the slow-roll order of the n-point correlation
function.Comment: 14 pages, 1 figure; typos corrected and discussion of tensor modes
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