Fully non-linear equivalence of delta N and covariant formalisms

Abstract

We explicitly show the fully non-linear equivalence of the $\delta$N and the covariant formalisms for the superhorizon curvature perturbations, which enables us to safely evaluate the non-Gaussian quantities of the curvature perturbation in either formalism. We also discuss isocurvature perturbations in the covariant formalism and clarify the relation between the fully non-linear evolution of the curvature covector and that of the curvature perturbation for multiple interacting fluids.

11 pages, minor changes, version accepted by PRD

References in corpus (14)

• Observational Signatures and Non-Gaussianities of General Single Field Inflation
• Non-Gaussianity in the modulated reheating scenario
• Primordial Curvature Fluctuation and Its Non-Gaussianity in Models with Modulated Reheating
• Probing String Theory with Modulated Cosmological Fluctuations
• Non-Gaussianity, Spectral Index and Tensor Modes in Mixed Inflaton and Curvaton Models
• Non-gaussianity from the second-order cosmological perturbation
• Primordial non-Gaussianity from the DBI Galileons
• Primordial non-Gaussianities in general modified gravitational models of inflation
• Primordial non-Gaussianity from G-inflation
• On Classification of Models of Large Local-Type Non-Gaussianity
• Nonlinear perturbations of cosmological scalar fields with non-standard kinetic terms
• Nonlinear perturbations for dissipative and interacting relativistic fluids
• Covariant generalization of cosmological perturbation theory
• δN versus covariant perturbative approach to non-Gaussianity outside the horizon in multifield inflation

Cited by in corpus (6)

• Nonperturbative analysis of the evolution of cosmological perturbations through a nonsingular bounce
• An update on adiabatic modes in cosmology and $\delta$N formalism
• Two-field inflation with non-minimal coupling
• A general proof of the equivalence between the δN and covariant formalisms
• $\Delta N$ Formalism and Conserved Currents in Cosmology
• Construction of the Conserved Non-linear Zeta via the Effective Action for Perfect Fluids