Halo nonlinear reconstruction
  We apply the nonlinear reconstruction method to simulated halo fields. For
halo number density $2.77\times 10^{-2}$ $(h^{-1} {\rm Mpc})^{-3}$ at $z=0$,
corresponding to the SDSS main sample density, we find the scale where the
noise saturates the linear signal is improved to $k\gtrsim0.36\ h {\rm
Mpc}^{-1}$, a factor of $2.29$ improvement in scale, or $12$ in number of
linear modes. The improvement is less for higher redshift or lower halo
density. We expect this to substantially improve the BAO accuracy of dense, low
redshift surveys, including the SDSS main sample, 6dFGS and 21cm intensity
mapping initiatives.
