Segmented strings and the McMillan map
  We present new exact solutions describing motions of closed segmented strings in $AdS_3$ in terms of elliptic functions. The existence of analytic expressions is due to the integrability of the classical equations of motion, which in our examples reduce to instances of the McMillan map. We also obtain a discrete evolution rule for the motion in $AdS_3$ of arbitrary bound states of fundamental strings and D1-branes in the test approximation. 
Steven S. Gubser, Sarthak Parikh, and Przemek Witaszczyk
hep-th