Non-gaussianity in axion Nflation models

Abstract

We study perturbations in the multi-field axion Nflation model, taking account of the full cosine potential. We find significant differences with previous analyses which made a quadratic approximation to the potential. The tensor-to-scalar ratio and the scalar spectral index move to lower values, which nevertheless provide an acceptable fit to observation. Most significantly, we find that the bispectrum non-gaussianity parameter f_NL may be large, typically of order 10 for moderate values of the axion decay constant, increasing to of order 100 for decay constants slightly smaller than the Planck scale. Such a non-gaussian fraction is detectable. We argue that this property is generic in multi-field models of hilltop inflation.

5 pages with 3 figures incorporated. v2: minor updates, new analytic formulae for spectral index and trispectrum, references added, typo corrections. v3: minor updates to match version accepted by Physical Review Letters

References in corpus (14)

• Non-Gaussianities in two-field inflation
• Non-Gaussianities in Multi-field Inflation
• Conditions for large non-Gaussianity in two-field slow-roll inflation
• CMB Constraints on Primordial non-Gaussianity from the Bispectrum (f_{NL}) and Trispectrum (g_{NL} and τ_{NL}) and a New Consistency Test of Single-Field Inflation
• Non-gaussianity from the inflationary trispectrum
• Large non-Gaussianity from two-component hybrid inflation
• On the Issue of the ζSeries Convergence and Loop Corrections in the Generation of Observable Primordial Non-Gaussianity in Slow-Roll Inflation. Part I: the Bispectrum
• Nflation: multi-field inflationary dynamics and perturbations
• Nflation: non-gaussianity in the horizon-crossing approximation
• Non-Gaussianities in N-flation
• On Perturbation Spectra of N-flation
• On the Issue of the ζSeries Convergence and Loop Corrections in the Generation of Observable Primordial Non-Gaussianity in Slow-Roll Inflation. Part II: the Trispectrum
• Nflation: observable predictions from the random matrix mass spectrum
• Stability of multi-field cosmological solutions

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• Non-Gaussianities in Multifield Inflation: Superhorizon Evolution, Adiabaticity, and the Fate of fnl
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• Perturbative Reheating After Multiple-Field Inflation: The Impact on Primordial Observables
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• The next non-Gaussianity frontier: what can a measurement with $\sigma (f_{\mathrm{NL}})\lesssim 1$ tell us about multifield inflation?
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• Large trispectrum in two-field slow-roll inflation
• Non-gaussianity in axion N-flation models: detailed predictions and mass spectra
• Adiabaticity and the Fate of Non-Gaussianities: The Trispectrum and Beyond
• No-boundary measure and preference for large e-foldings in multi-field inflation
• Primordial curvature perturbation during and at the end of multi-field inflation
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• Multi-fluid cosmology in Einstein gravity: analytical solutions
• The probability distribution for non-Gaussianity estimators constructed from the CMB trispectrum
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• Exploring Two-Field Inflation in the Wess-Zumino Model
• What Planck does not tell us about inflation
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• Evidence for Inflation in an Axion Landscape
• Towards an Observational Appraisal of String Cosmology
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