Simple Properties: structure of the action

We postulate the action of the form:

(1) This is almost a generic sigma-model, but we require:

  1. Classical 2d conformal invariance

  2. Lagrangian is polynomial in and

  3. Two separate conserved ghost number charges:
    • left ghost charge for

    • right ghost charge for

and the most important postulate is about:

 BRST structure