Analyzing the cosmic variance limit of remote dipole measurements of the
  cosmic microwave background using the large-scale kinetic Sunyaev Zel'dovich
  effect
  Due to cosmic variance we cannot learn any more about large-scale
inhomogeneities from the primary cosmic microwave background (CMB) alone. More
information on large scales is essential for resolving large angular scale
anomalies in the CMB. Here we consider cross correlating the large-scale
kinetic Sunyaev Zel'dovich (kSZ) effect and probes of large-scale structure, a
technique known as kSZ tomography. The statistically anisotropic component of
the cross correlation encodes the CMB dipole as seen by free electrons
throughout the observable Universe, providing information about long wavelength
inhomogeneities. We compute the large angular scale power asymmetry,
constructing the appropriate transfer functions, and estimate the cosmic
variance limited signal to noise for a variety of redshift bin configurations.
The signal to noise is significant over a large range of power multipoles and
numbers of bins. We present a simple mode counting argument indicating that kSZ
tomography can be used to estimate more modes than the primary CMB on
comparable scales. A basic forecast indicates that a first detection could be
made with next-generation CMB experiments and galaxy surveys. This paper
motivates a more systematic investigation of how close to the cosmic variance
limit it will be possible to get with future observations.
