Conservation of the nonlinear curvature perturbation in generic single-field inflation

Abstract

It is known that the curvature perturbation on uniform energy density (or comoving or uniform Hubble) slices on superhorizon scales is conserved to full nonlinear order if the pressure is only a function of the energy density (ie, if the perturbation is purely adiabatic), independent of the gravitational theory. Here we explicitly show that the same conservation holds for a universe dominated by a single scalar field provided that the field is in an attractor regime, for a very general class of scalar field theories. However, we also show that if the scalar field equation contains a second time derivative of the metric, as in the case of the Galileon theory, one has to invoke the gravitational field equations to show the conservation.

6 pages, minor revisions made but conclusion unchanged, references added, to be published in CQG as a fast track communication

References in corpus (10)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Imperfect Dark Energy from Kinetic Gravity Braiding
• G-inflation: inflation driven by the Galileon field
• Non-gaussianity from the second-order cosmological perturbation
• Primordial non-Gaussianity from the DBI Galileons
• Primordial Non-Gaussianity in Multi-Scalar Slow-Roll Inflation
• Gradient expansion approach to nonlinear superhorizon perturbations
• Non-Gaussianity of superhorizon curvature perturbations beyond $\delta$ N formalism
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• Nonlinear superhorizon perturbations of non-canonical scalar field

Cited by in corpus (10)

• Horndeski theory and beyond: a review
• Primordial black holes and gravitational waves from resonant amplification during inflation
• Primordial non-Gaussianities in general modified gravitational models of inflation
• Primordial non-Gaussianity from G-inflation
• Potential-driven Galileon inflation
• Disformal transformation of cosmological perturbations
• Multi-field effects in a simple extension of $R^2$ inflation
• Holographic inflation and the conservation of $\zeta$
• Running of scalar spectral index in multi-field inflation
• The spatial gauge-dependence of single-field inflationary bispectra