  The hierarchical cold dark matter (CDM) model for structure formation is a
well defined and testable model. Direct detection is the best technique for
confirming the model yet predictions for the energy and density distribution of
particles on earth remain inadequate. Axially symmetric collapse of
collisionless dark matter can leave observable caustic rings in phase space and
this model is frequently used to make experimental predictions (Sikivie 1999).
Such cold collapses inevitably suffer from radial orbit instabilities that
produce unrealistic bar-like halos. Moreover, this model bears no relation to
the hierarchical growth of CDM galactic halos which form via a complicated
sequence of mergers and violent relaxation. This process destroys any symmetry
and phase wraps existing caustics on a scale comparable to the first objects to
collapse. Since axions can cluster on microscopic scales and free streaming of
neutralinos only erases structure smaller than \sim 100 (GeV/m_{CDM}) A.U., the
dynamical effects of caustics in the Galactic halo are expected to be
negligible.
