  We consider actions for particles and strings, including twistorial
descriptions on 4d Minkowski and AdS$_5$ spacetimes from the point of view of
co-adjoint 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.
