  A procedure for constructing topological actions from centrally extended Lie
groups is introduced. For a \km\ group, this produces \3al \cs, while for the
\vir\ group the result is a new \3al \tft\ whose physical states satisfy the
\vir\ \wi. This \tft\ is shown to be a first order formulation of two
dimensional induced gravity in the chiral gauge. The extension to $W_3$-gravity
is discussed.

High Energy Physics - Theory