We investigate numerically the dynamically generated plastic deformations of
a 3D vortex lattice (VL) driven through a disorder potential with isolated,
strong pinning centers (point-like or extended along the field direction). We
find that the VL exhibits a very peculiar dynamical behavior in the plastic
flow regime, in particular, topological excitations consisting of three or four
entangled vortices are formed. We determine the critical current density jc
and the activation energy for depinning Uc in the presence of a finite
density of strong pinning centers.Comment: 12 pages, TeX type, Postscript figure