Double inflation and the low CMB multipoles

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 show that these potentials allow a period of fast roll sandwiched between two stages of slow roll inflation. We find that the modes which exit the Hubble radius during the period of fast roll have lower power when comparedto the amplitude of the nearly scale invariant spectrum associated with the modes that leave during the second stage of slow roll inflation. We set the scales such that the drop in the scalar 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, χ2 eff improves by 6.62) of the observed data when compared to the best fit reference ΛCDM model with a featureless, power law, primordial spectrum.