δN versus covariant perturbative approach to non-Gaussianity outside the horizon in multifield inflation

Abstract

We compute the super-Hubble evolution of non-Gaussianity of primordial curvature perturbations in two-field inflation models by employing two formalisms: delta N and covariant formalisms. Although two formalisms treat the evolution of fluctuations radically different, we show that the formulas of f_{NL} parameter agree quantitatively with each other within 1 % accuracy. We analytically find that the amplitude of f_{NL} decays no faster than a^{-3} as the inflationary trajectory reaches to the adiabatic limit for generic potentials.

v4: minor changes, version accepted for PRD; v3: 10 pages, 14 figures, added two examples that produce relatively large non-Gaussianity in Appendix to support the results; v2: 8 pages, 10 figures, added references

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Cited by in corpus (14)

• Correlation Functions in Stochastic Inflation
• Perturbative Reheating After Multiple-Field Inflation: The Impact on Primordial Observables
• Squeezed Bispectrum in the $\delta N$ Formalism: Local Observer Effect in Field Space
• Reheating, Multifield Inflation and the Fate of the Primordial Observables
• Large trispectrum in two-field slow-roll inflation
• Multi-field effects in a simple extension of $R^2$ inflation
• Local non-Gaussianity from rapidly varying sound speeds
• Multi-field formulation of gravitational particle production after inflation
• Influence of Reheating on the Trispectrum and its Scale Dependence
• Mixed non-Gaussianity in multiple-DBI inflation
• Fully non-linear equivalence of delta N and covariant formalisms
• A general proof of the equivalence between the δN and covariant formalisms
• Covariant second-order perturbations in generalized two-field inflation
• Curvature Perturbations in the Effective Field Theory of Inflation