Nonlinear superhorizon perturbations of non-canonical scalar field

Abstract

We develop a theory of non-linear cosmological perturbations at superhorizon scales for a scalar field with a Lagrangian of the form $P(X,\varphi )$, where $X=-{\partial }^{\mu }\varphi {\partial }_{\mu }\varphi$ and $\varphi$ is the scalar field. We employ the ADM formalism and the spatial gradient expansion approach to obtain general solutions valid up to the second order in the gradient expansion. This formulation can be applied to, for example, DBI inflation models to investigate superhorizon evolution of non-Gaussianities. With slight modification, we also obtain general solutions valid up to the same order for a perfect fluid with a general equation of state $P=P(\rho )$.

14 pages

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Cited by in corpus (5)

• On Classification of Models of Large Local-Type Non-Gaussianity
• Conservation of the nonlinear curvature perturbation in generic single-field inflation
• Non-Gaussianity of superhorizon curvature perturbations beyond $\delta$ N formalism
• Full nonlinear growing and decaying modes of superhorizon curvature perturbations
• Tackling non-linearities with the effective field theory of dark energy and modified gravity