  Entangled networks of stiff biopolymers exhibit complex dynamic response,
emerging from the topological constraints that neighboring filaments impose
upon each other. We propose a class of reference models for entanglement
dynamics of stiff polymers and provide a quantitative foundation of the tube
concept for stiff polymers. For an infinitely thin needle exploring a planar
course of point obstacles, we have performed large-scale computer simulations
proving the conjectured scaling relations from the fast transverse
equilibration to the slowest process of orientational relaxation. We determine
the rotational diffusion coefficient of the tracer, its angular confinement,
the tube diameter and the orientational correlation functions.
