Segmented strings in AdS3

We study segmented strings in flat space and in AdS3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS2 subspace of AdS3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We study several examples of closed segmented strings in AdS3 and find an unexpected quasi-periodic behavior. We also work out a WKB analysis of quantum states of yo-yo strings in AdS5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.