  We perform a numerical study of the critical regime for the general
relativistic collapse of collisionless matter in spherical symmetry. The
evolution of the matter is given by the Vlasov equation (or Boltzmann equation)
and the geometry by Einstein's equations. This system of coupled differential
equations is solved using a particle-mesh (PM) method. This method approximates
the distribution function which describes the matter in phase space with a set
of particles moving along the characteristics of the Vlasov equation. The
individual particles are allowed to have angular momentum different from zero
but the total angular momentum has to be zero to retain spherical symmetry.
  In accord wih previous work by Rein, Rendall and Schaeffer, our results give
some indications that the critical behaviour in this model is of Type I (the
smallest black hole in each family has a finite mass). For the families of
initial data that we have studied it seems that in the critical regime the
solution is a static spacetime with non-zero radial momentum for the individual
particles. We have also found evidence for scaling laws for the time that the
critical solutions spend in the critical regime.
