## 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.

src,
ps,
pdf