CMB polarization as a direct test of Inflation

Abstract

We study the auto-correlation function of CMB polarization anisotropies and their cross correlation with temperature fluctuations as probe of the causal structure of the universe. Because polarization is generated at the last scattering surface, models in which fluctuations are causally produced on sub-horizon scales cannot generate correlations on scales larger then $\sim 2^o$. Inflationary models, on the other hand, predict a peak in the correlation functions at these scales: its detection would be definitive evidence in favor of a period of inflation. This signal could be detected with the next generation of satellites.

Figures (1)

• Figure 1: Correlation functions for Q (a) and U (b) Stokes parameters for sCDM and the causal seed model discussed in the text. The noise in their determination is shown for both MAP and Planck. Panel (b) shows the expected noise for MAP if the CMB maps are flltered to include only the $E$ channel signal. Panel (c) shows the cross correlation between temperature and polarization and the noise for MAP, the expected variance for Planck is even smaller. Each resolution element in the correlation function should be considered independent.