Punctuated inflation and the low CMB multipoles

TL;DR

This paper explores inflationary models with brief departures from slow roll, producing a step-like feature in the power spectrum that better explains the low quadrupole power in the CMB, fitting WMAP data more accurately.

Contribution

It introduces a class of inflationary potentials causing a temporary departure from slow roll, resulting in a step in the power spectrum that improves CMB data fit.

Findings

Better fit to WMAP data with a suppressed large-scale power spectrum.

Introduction of a brief departure from slow roll causes a step in the scalar power spectrum.

Improved fit with just one extra parameter, reducing chi-squared by 6.62.

Abstract

We investigate inflationary scenarios driven by a class of potentials which are similar in form to those that arise in certain minimal supersymmetric extensions of the standard model. We find that these potentials allow a brief period of departure from inflation sandwiched between two stages of slow roll inflation. We show that such a background behavior leads to a step like feature in the scalar power spectrum. We set the scales such that the drop in the power spectrum occurs at a length scale that corresponds to the Hubble radius today--a feature that seems necessary to explain the lower power observed in the quadrupole moment of the Cosmic Microwave Background (CMB) anisotropies. We perform a Markov Chain Monte Carlo analysis to determine the values of the model parameters that provide the best fit to the recent WMAP 5-year data for the CMB angular power spectrum. We find that an inflationary spectrum with a suppression of power at large scales that we obtain leads to a much better fit (with just one extra parameter, $\chi_{\rm eff}^{2}$ improves by 6.62) of the observed data when compared to the best fit reference $\Lambda$CDM model with a featureless, power law, primordial spectrum.