Rules of the game: BRST structure

We require two symmetries and which should:

1. have certain ghost charges:

   	left ghost #	right ghost #
   	1	0
   	0	1

2. satisfy the constraint: where

The existence of such and in the classical sigma-model imposes constraints on the coefficients , , ,

It turns out that these constraints guarantee that these coefficients encode the solutions of the Type IIB SUGRA. At the quantum level, the condition encodes the stringy -corrections. (N.Berkovits, P.Howe)