Review: Mean-Square Displacements of Simulated Polymers.

We review simulations of polymeric fluids that report mean-square displacements g(t) of polymer beads, segments, and chains. By means of careful numerical analysis, but contrary to some models of polymer dynamics, we show that hypothesized power-law regimes g(t)∼tα are almost never present. In most but not quite all cases, plots of log(g(t)) against log(t) show smooth curves whose slopes vary continuously with time. We infer that models that predict power-law regimes for g(t) are invalid for melts of linear polymers.