Running primordial perturbations: Inflationary Dynamics and Observational Constraints

Abstract

Inflationary cosmology proposes that the early Universe undergoes accelerated expansion, driven, in simple scenarios, by a single scalar field, or inflaton. The form of the inflaton potential determines the initial spectra of density perturbations and gravitational waves. We show that constraints on the duration of inflation together with the BICEP3/Keck bounds on the gravitational wave background imply that higher derivatives of the potential are nontrivial with a confidence of 99%. Such terms contribute to the scale-dependence, or running, of the density perturbation spectrum. We clarify the ``universality classes'' of inflation in this limit showing that a very small gravitational wave background can be correlated with a larger running. If pending experiments do not observe a gravitational wave background the running will be at the threshold of detectability if inflation is well-described at third-order in the slow roll expansion.

5 pages; 5 figures; as published in PRD -- change of title, minor clarifications

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• BICEP / Keck XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
• Inflation and the Scale Dependent Spectral Index: Prospects and Strategies
• Collapse of Small-Scale Density Perturbations during Preheating in Single Field Inflation
• Lighting the Dark: The Evolution of the Post-Inflationary Universe
• Constraining Inflation
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Cited by in corpus (12)

• Simple single-field inflation models with arbitrarily small tensor/scalar ratio
• Oscillon formation from preheating in asymmetric inflationary potentials
• LiteBIRD and CMB-S4 Sensitivities to Reheating in Plateau Models of Inflation
• Constraining Cosmic Inflation with Observations: Prospects for 2030
• Searching for blue in the dark
• Chasing cosmic inflation: constraints for inflationary models and reheating insights
• Minimizing the tensor-to-scalar ratio in single-field inflation models
• Third-order corrections to the slow-roll expansion: calculation and constraints with Planck, ACT, SPT, and BICEP/Keck
• Natural Inflation with Exponentially Small Tensor-To-Scalar Ratio
• Reheating constraints on mutated hilltop inflation
• One Extension to Explain Them All, One Scale-Invariant Spectrum to Test Them All, and in One Model Bind Them
• Observational constraints on the second-order primordial power spectrum: Exploring a Continuous Spontaneous Localization inspired inflationary model