Complete WMAP Constraints on Bandlimited Inflationary Features

TL;DR

This paper uses WMAP7 data and principal component analysis to test for features in the inflationary potential, finding no significant deviations from slow roll but providing model-independent constraints on potential features.

Contribution

It introduces a comprehensive, model-independent method to constrain inflationary features using principal components and WMAP data, applicable to a wide range of models.

Findings

No statistically significant inflationary features detected.

Constraints placed on step-like potential features.

Predictions for polarization spectrum glitches tested against data.

Abstract

Using a principal component (PC) basis that accommodates order unity features in the slow roll parameters as fine as 1/10 of a decade across more than 2 decades of the inflationary expansion, we test slow roll and single field inflation with the WMAP7 data. Detection of any non-zero component would represent a violation of ordinary slow roll and indicate a feature in the inflaton potential or sound speed. Although one component shows a deviation at the 98% CL, it cannot be considered statistically significant given the 20 components tested. The maximum likelihood PC parameters only improves 2DeltalnL by 17 for the 20 parameters associated with known glitches in the WMAP power spectrum at multipoles l<60. We make model-independent predictions for the matching glitches in the polarization spectrum that would test their inflationary origin. This complete analysis for bandlimited features in the source function of generalized slow roll can be used to constrain parameters of specific models of the inflaton potential without requiring a separate likelihood analysis for each choice. We illustrate its use by placing bounds on the height and width of a step-like feature in the potential proposed to explain the glitch at 20<l<40. Even allowing for the presence of features in the temperature spectrum, single field inflation makes sharp falsifiable predictions for the acoustic peaks in the polarization whose violation would require extra degrees of freedom.