  Molecular dynamics simulations were performed for a polymer melt. In
quiescent states, the inter-chain interaction energy supported by each particle
takes relatively large values persistently for long times if the particle is
close to an entanglement. Thus, if the interaction is averaged over appropriate
time intervals, we can detect active spots on the chains produced by
entanglement constrains. If rapid shearing is applied, these active regions
subsequently become bended in eventual zig-zag shapes of the chains. We also
demonstrate that stress overshoot occurs with onset of disentanglement.
