Fluctuating semiflexible polymer ribbon constrained to a ring

Twist stiffness and an asymmetric bending stiffness of a polymer or
a polymer bundle is captured by the elastic ribbon model. We
investigate the effects a ring geometry induces to a thermally
fluctuating ribbon, finding bend-bend coupling in addition to
twist-bend coupling. Furthermore, due to the geometric constraint
the polymer's effective bending stiffness increases. A new
parameter for experimental investigations of polymer bundles is
proposed: the mean square diameter of a ribbonlike ring, which is
determined analytically in the semiflexible limit. Monte Carlo
simulations are performed which affirm the model's prediction up to
high flexibility.