The path towards manifest background independence
arXiv:hep-th/9709215
Abstract
The set of string vertices is extended to include moduli spaces with genus and numbers of ordinary and special punctures ranging over all integral values . It is argued that both the string background and the B-V delta operator should be associated with the vertex $\B^0_{0,1}$ corresponding to the once-punctured sphere. This leads naturally to the proposal that the manifestly background independent formulation of quantum closed string field theory is given by the sum $\B$ of the completed set of string vertices satisfying the classical master equation $\{\B,\B\}=0$.
9 pages, phyzzx