Microwave Background Polarization as a Probe of Large-Angle Correlations
  Two-point correlation functions of cosmic microwave background polarization
provide a physically independent probe of the surprising suppression of
correlations in the cosmic microwave background temperature anisotropies at
large angular scales. We investigate correlation functions constructed from
both the Q and U Stokes parameters and from the E and B polarization
components. The dominant contribution to these correlation functions comes from
local physical effects at the last scattering surface or from the epoch of
reionization at high redshift, so all should be suppressed if the temperature
suppression is due to an underlying lack of correlations in the cosmological
metric perturbations larger than a given scale. We evaluate the correlation
functions for the standard $\Lambda$CDM cosmology constrained by the observed
temperature correlation function, and compute statistics characterizing their
suppression on large angular scales. Future full-sky polarization maps with
minimal systematic errors on large angular scales will provide strong tests of
whether the observed temperature correlation function is a statistical fluke or
reflects a fundamental shortcoming of the standard cosmological model.
