1303.6628 (Noemi Frusciante et al.)

Gradient expansion of superhorizon perturbations in G-inflation    [PDF]

Noemi Frusciante, Shuang-Yong Zhou, Thomas P. Sotiriou

We develop the gradient expansion formalism for shift-symmetric Galileon-type actions. We focus on backgrounds that undergo inflation, work in the synchronous gauge, and obtain a general solution up to second order without imposing extra conditions at first order. The solution simplifies during the late stages of inflation. We also define a curvature perturbation conserved up to first order.

View original: http://arxiv.org/abs/1303.6628