Stable knots in the phase diagram of semiflexible polymers: A topological order parameter?

Abstract

We report a recent computer simulation study of the phase diagram of a single semiflexible polymer chain using a generic coarse-grained bead-stick model. The results are obtained with a combination of multicanonical and replica-exchange simulations. Interestingly, we find in the temperature-stiffness plane well-defined phases that can be characterized by stable knots of various types. We discuss how the knots can be observed and to what extent they can be interpreted as “topological order parameter”. Another surprising observation concerns the peculiar transitions into these stable knot phases which will be also explained.