CMB polarization features from inflation versus reionization

Understand

The angular power spectrum of the cosmic microwave background temperature anisotropy observed by WMAP has an anomalous dip at l~20 and bump at l~40.

• One explanation for this structure is the presence of features in the primordial curvature power spectrum, possibly caused by a step in the inflationary potential.
• The detection of these features is only marginally significant from temperature data alone.
• However, the inflationary feature hypothesis predicts a specific shape for the E-mode polarization power spectrum with a structure similar to that observed in temperature at l~20-40.