  The predicted central densities of dark matter halos in LCDM models exceed
those observed in some galaxies. Weinberg & Katz argue that angular momentum
transfer from a rotating bar in the baryonic disk can lower the halo density,
but they also contend that N-body simulations of this process will not reveal
the true continuum result unless many more than the usual numbers of particles
are employed. Adopting their simplified model of a rotating rigid bar in a live
halo, I have been unable to find any evidence to support their contention. I
find that both the angular momentum transferred and the halo density change are
independent of the number of particles over the range usually employed up to
that advocated by these authors. I show that my results do not depend on any
numerical parameters, and that field methods perform equally with grid methods.
I also identify the reasons that the required particle number suggested by
Weinberg & Katz is excessive. I further show that when countervailing
compression by baryonic settling is ignored, moderate bars can reduce the mean
density of the inner halo by 20% - 30%. Long, massive, skinny bars can reduce
the mean inner density by a factor ~10. The largest density reductions are
achieved at the expense of removing most of the angular momentum likely to
reside in the baryonic component. Compression of the halo by baryonic settling
must reduce, and may even overwhelm, the density reduction achievable by bar
friction.
