Actions for particles and strings and Chern-Simons gravity

We consider actions for particles and strings, including twistorial descriptions on 4D Minkowski and ${\mathrm{AdS}}_5$ spacetimes from the point of view of coadjoint orbits for the isometry group. We also consider the collective coordinate dynamics of singular solutions in Chern-Simons (CS) theories and CS theories of gravity. This is a generalization of the work of Einstein, Infeld, and Hoffmann and also has potential points of contact with fluid-gravity correspondence.