The High-Redshift Neutral Hydrogen Signature of an Anisotropic Matter
  Power Spectrum
  An anisotropic power spectrum will have a clear signature in the 21cm
radiation from high-redshift hydrogen. We calculate the expected power spectrum
of the intensity fluctuations in neutral hydrogen from before the epoch of
reionization, and predict the accuracy to which future experiments could
constrain a quadrupole anisotropy in the power spectrum. We find that the
Square Kilometer Array will have marginal detection abilities for this signal
at z~17 if the process of reionization has not yet started; reionization could
enhance the detectability substantially. Pushing to higher redshifts and higher
sensitivity will allow highly precise (percent level) measurements of
anisotropy.
