Effects of local features of the inflaton potential on the spectrum and bispectrum of primordial perturbations

TL;DR

This paper investigates how local features in the inflaton potential, characterized by a symmetric step with an exponential decay, influence the primordial power spectrum and bispectrum, affecting CMB observations.

Contribution

It introduces and analyzes a new class of local features in the inflaton potential, showing their specific impact on primordial perturbations and CMB spectra, distinct from previously studied branch-type features.

Findings

Local features cause oscillations in the power spectrum around a specific scale.

Effects are confined to a narrow range of scales corresponding to the feature.

Different parameter choices lead to observable variations in CMB temperature and polarization spectra.

Abstract

We study the effects of a class of features of the potential of slow-roll inflationary models corresponding to a step symmetrically dumped by an even power negative exponential factor, which we call local features. Local-type features differ from other branch-type features considered previously, because the potential is only affected in a limited range of the scalar field value, and are symmetric respect to the location of the feature. This type of features only affects the spectrum and bispectrum in a narrow range of scales which leave the horizon during the time interval corresponding to the modification of the potential. On the contrary branch-type features have effects on all the perturbation modes leaving the horizon when the field value is within the interval defining the branch, introducing for example differences in the power spectrum between large and small scale which are absent in the case of local-type features. The spectrum and bispectrum of primordial curvature perturbations are affected by oscillations around the scale $k_0$ exiting the horizon at the time $\tau_0$ corresponding to the feature. We also compute the effects of the features on the CMB temperature and polarization spectra, showing the effects or different choices of parameters.