Exploring the CMB Power Suppression in Canonical Inflation Models

Abstract

There exists some evidence of a suppression in power in the CMB multipoles around $l\sim 20-30$. If taken seriously, this is in tension with the simplest inflationary models driven by a single scalar field with a standard type of slowly varying potential function $V(\varphi )$. Such potential functions generate a nearly scale invariant spectrum and so they do not possess the requisite suppression in power. In this paper we explore if canonical two-derivative inflation models, with a step-like feature in the potential, can improve agreement with data. We find that improvement can be made when one utilizes the standard slow-roll approximation formula for the power spectrum. However, we find that in order to have a feature in the power spectrum that is sufficiently localized so as to not significantly disrupt higher $l$ or lower $l$, the potential's step-like feature must be so sharp that the standard slow-roll approximations break down. This leads us to perform an exact computation of the power spectrum by solving for the Bunch-Davies mode functions numerically. We find that the corresponding CMB multipoles do not provide a good agreement with the data. We conclude that, unless there is fine-tuning, canonical inflation models do not fit this suppression in the data.

arXiv comment17 pages, 7 figures. V2: Updated towards version published in JCAP

References in corpus (16)

• Planck 2015 results. XIII. Cosmological parameters
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• The Cosmic Linear Anisotropy Solving System (CLASS) II: Approximation schemes
• Cosmological Non-Linearities as an Effective Fluid
• The Effective Field Theory of Cosmological Large Scale Structures
• Features and New Physical Scales in Primordial Observables: Theory and Observation
• Primordial Black Holes from Polynomial Potentials in Single Field Inflation
• The Spectrum of Density Perturbations produced during Inflation to Leading Order in a General Slow-Roll Approximation
• The Effective Field Theory of Dark Matter and Structure Formation: Semi-Analytical Results
• Primeval Corrections to the CMB Anisotropies
• Consistency relations for sharp features in the primordial spectra
• Searching for Oscillations in the Primordial Power Spectrum with CMB and LSS Data
• Scalar suppression on large scales in open inflation
• Low-$\ell$ power suppression in punctuated inflation
• Primordial Non-Gaussianities of inflationary step-like models
• Large Scale Power Suppression in a Multifield Landscape