Reconstructing the Primary CMB Dipole
  The observed dipole anisotropy of the cosmic microwave background (CMB)
temperature is much larger than the fluctuations observed on smaller scales and
is dominated by the kinematic contribution from the Doppler shifting of the
monopole due to our motion with respect to the CMB rest frame. In addition to
this kinematic component, there is expected to be an intrinsic contribution
with an amplitude about two orders of magnitude smaller. Here we explore a
method whereby the intrinsic CMB dipole can be reconstructed through
observation of temperature fluctuations on small scales which result from
gravitational lensing. Though the experimental requirements pose practical
challenges, we show that one can in principle achieve a cosmic variance limited
measurement of the primary dipole using the reconstruction method we describe.
Since the primary CMB dipole is sensitive to the largest observable scales,
such a measurement would have a number of interesting applications for early
universe physics, including testing large-scale anomalies, extending the
lever-arm for measuring local non-Gaussianity, and constraining isocurvature
fluctuations on super-horizon scales.
