Rules of the game: BRST structureWe require two symmetries and which should:

have certain ghost charges:

left ghost #

right ghost #

1

0

0

1

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)