Entropic Tightening of Vibrated Chains,

M. B. Hastings, Z. A. Daya, E. Ben-Naim, and R. E. Ecke

We investigate experimentally the distribution of configurations of a ring with an elementary topological constraint, a ``figure-8'' twist. Using a system far from thermal equilibrium, a vibrated granular chain, we show that configurations where one loop is small and the second is large are strongly preferred. Despite the highly non-equilibrium nature of the system, our results are consistent with recent predictions for equilibrium properties of topologically-constrained polymers. The dynamics of the tightening process weakly violates a (coarse-grained) detailed balance, indicating that the unexpected correspondence with an equilibrium entropic approach is not exact.

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