  Non-Abelian plasma instabilities have been proposed as a possible explanation
for fast isotropization of the quark-gluon plasma produced in relativistic
heavy-ion collisions. We study the real-time evolution of these instabilities
in non-Abelian plasmas with a momentum-space anisotropy using a hard-loop
effective theory that is discretized in the velocities of hard particles. We
extend our previous results on the evolution of the most unstable modes, which
are constant in directions transverse to the direction of anisotropy, from
gauge group SU(2) to SU(3). We also present first full 3+1-dimensional
simulation results based on velocity-discretized hard loops. In contrast to the
effectively 1+1-dimensional transversely constant modes we find subexponential
behaviour at late times.
