Lagrangian Symmetries of Chern-Simons Theories

This paper analyses the Noether symmetries and the corresponding conservation laws for Chern-Simons Lagrangians in dimension $d=3$. In particular, we find an expression for the superpotential of Chern-Simons gravity. As a by-product the general discussion of superpotentials for 3rd order natural and quasi-natural theories is also given.Comment: 16 pages in LaTeX, some comments and references added. to appear in Journal of Physics A: Mathematical and Genera