Nonlinear superhorizon curvature perturbation in generic single-field inflation

Abstract

We develop a theory of nonlinear cosmological perturbations on superhorizon scales for generic single-field inflation. Our inflaton is described by the Lagrangian of the form $W(X,\varphi )-G(X,\varphi )\square \varphi$ with $X=-{\partial }^{\mu }\varphi {\partial }_{\mu }\varphi /2$, which is no longer equivalent to a perfect fluid. This model is more general than k-inflation, and is called G-inflation. A general nonlinear solution for the metric and the scalar field is obtained at second order in gradient expansion. We derive a simple master equation governing the large-scale evolution of the nonlinear curvature perturbation. It turns out that the nonlinear evolution equation is deduced as a straightforward extension of the corresponding linear equation for the curvature perturbation on uniform $\varphi$ hypersurfaces.

14 pages, version to appear in PTEP

References in corpus (9)

• G-inflation: inflation driven by the Galileon field
• Higgs G-inflation
• Non-gaussianity from the second-order cosmological perturbation
• Primordial non-Gaussianity from the DBI Galileons
• Primordial non-Gaussianity from G-inflation
• Gradient expansion approach to nonlinear superhorizon perturbations
• Conservation of the nonlinear curvature perturbation in generic single-field inflation
• Gradient expansion approach to nonlinear superhorizon perturbations II -- a single scalar field --
• Full nonlinear growing and decaying modes of superhorizon curvature perturbations

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• Large fluctuations and Primordial Black Holes
• Regularized-Renormalized-Resummed loop corrected power spectrum of non-singular bounce with Primordial Black Hole formation
• Primordial Black Holes from Effective Field Theory of Stochastic Single Field Inflation at NNNLO
• Negative non-Gaussianity as a salvager for PBHs with PTAs in bounce
• Constraining cosmological scaling solutions of a Galileon field
• Gradient expansion of superhorizon perturbations in G-inflation
• Inflation in Non-de Sitter Background with Coherent States
• Application of beyond $\delta N$ formalism -- Varying sound speed