Inflationary signatures of single-field models beyond slow-roll

Abstract

If the expansion of the early Universe was not close to de Sitter, the statistical imprints of the primordial density perturbation on the cosmic microwave background can be quite different from those derived in slow-roll inflation. In this paper we study the inflationary signatures of all single-field models which are free of ghost-like instabilities. We allow for a rapid change of the Hubble parameter and the speed of sound of scalar fluctuations, in a way that is compatible with a nearly scale-invariant spectrum of perturbations, as supported by current cosmological observations. Our results rely on the scale-invariant approximation, which is different from the standard slow-roll approximation. We obtain the propagator of scalar fluctuations and compute the bispectrum, keeping next-order corrections proportional to the deviation of the spectral index from unity. These theories offer an explicit example where the shape and scale-dependences of the bispectrum are highly non-trivial whenever slow-roll is not a good approximation.

v1: 36 pages, including tables, appendices and references. v2: abstract improved, references added, minor clarifications throughout the text; matches version published in JCAP

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Cited by in corpus (35)

• Beyond the Cosmological Standard Model
• Ultra Slow-Roll Inflation and the non-Gaussianity Consistency Relation
• Features and New Physical Scales in Primordial Observables: Theory and Observation
• Shapes of primordial non-Gaussianities in the Horndeski's most general scalar-tensor theories
• Localized correlated features in the CMB power spectrum and primordial bispectrum from a transient reduction in the speed of sound
• Bispectrum in Single-Field Inflation Beyond Slow-Roll
• On the scalar consistency relation away from slow roll
• Collective Symmetry Breaking and Resonant Non-Gaussianity
• Untangling features in the primordial spectra
• Strong scale dependent bispectrum in the Starobinsky model of inflation
• Non-slow-roll dynamics in $\alpha -$attractors
• Searching for primordial localized features with CMB and LSS spectra
• The δN formula is the dynamical renormalization group
• The squeezed limit of the bispectrum in multi-field inflation
• Transporting non-Gaussianity from sub to super-horizon scales
• General formula for the running of local fNL
• Three-form inflation and non-Gaussianity
• Observational constraints on tachyon and DBI inflation
• Effect of transitions in the Planck mass during inflation on primordial power spectra
• Local non-Gaussianity from rapidly varying sound speeds
• The Separate Universe Approach to Soft Limits
• Primordial Power Spectrum features and $f_{NL}$ constraints
• Beyond the growth rate of cosmic structure: Testing modified gravity models with an extra degree of freedom
• Non-Canonical Inflation in Supergravity
• Scale-dependent bias from multiple-field inflation
• DBI Galileon inflation in the light of Planck 2015
• Non-Gaussian Shape Recognition
• Non-Gaussian Shape Discrimination with Spectroscopic Galaxy Surveys
• Why does the effective field theory of inflation work?
• Scalar Bispectrum Beyond Slow-Roll in the Unified EFT of Inflation
• Quantum quenches during inflation
• Resonant non-Gaussianity with equilateral properties
• Looking for non-Gaussianity in all the right places: A new basis for non-separable bispectra
• Application of beyond $\delta N$ formalism -- Varying sound speed
• Constraining fast-roll inflation