Perturbative Unitarity of Inflationary Models with Features

Abstract

We consider the pertubative consistency of inflationary models with features with effective field theory methods. By estimating the size of one-loop contributions to the three-point function, we find the energy scale where their contribution is of the same order of the tree-level amplitude. It is well-known that beyond that scale, perturbative unitarity is lost and the theory is no more under theoretical control. Requiring that all the relevant energy scales of the problem are below this cutoff, we derive a strong upper bound on the sharpness of the feature, or equivalently on its characteristic time scale, which is independent on the amplitude of the feature itself. We point out that the sharp features which seem to provide better fits to the CMB power spectrum are already outside this bound, questioning the consistency of the models that predict them.

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Cited by in corpus (11)

• Oscillations in the stochastic gravitational wave background from sharp features and particle production during inflation
• B-modes and the Nature of Inflation
• Polyspectra searches for sharp oscillatory features in cosmic microwave sky data
• Inflation in Motion: Unitarity Constraints in Effective Field Theories with Broken Lorentz Symmetry
• Searching for primordial localized features with CMB and LSS spectra
• Euclid: The search for primordial features
• Bayesian reconstruction of the inflaton's speed of sound using CMB data
• Robust predictions for an oscillatory bispectrum in Planck 2015 data from transient reductions in the speed of sound of the inflaton
• Perturbative unitarity and NEC violation in genesis cosmology
• Primordial feature constraints from BOSS+eBOSS
• Primordial gravitational waves from excited states