Particle Models and the Small-Scale Structure of Dark Matter
  The kinetic decoupling of weakly interacting massive particles (WIMPs) in the
early universe sets a scale that can directly be translated into a small-scale
cutoff in the spectrum of matter density fluctuations. The formalism presented
here allows a precise description of the decoupling process and thus the
determination of this scale to a high accuracy from the details of the
underlying WIMP microphysics. With decoupling temperatures of several MeV to a
few GeV, the smallest protohalos to be formed range between 10^{-11} and almost
10^{-3} solar masses -- a somewhat smaller range than what was found earlier
using order-of-magnitude estimates for the decoupling temperature; for a given
WIMP model, the actual cutoff mass is typically about a factor of 10 greater
than derived in that way, though in some cases the difference may be as large
as a factor of several 100. Observational consequences and prospects to probe
this small-scale cutoff, which would provide a fascinating new window into the
particle nature of dark matter, are discussed
