Narrow Results

We explore the geometry of superconformal moduli of the NSR superstring theory in order to construct the consistent sigma-model for NSR strings, free of picture-changing complications. The sigma-model generating functional is constructed by the integration over the bosonic and fermionic moduli, corresponding to insertions of the vertex operators in scattering amplitudes. While the integration over the supermoduli leads to the standard picture-changing insertions, the integration over the bosonic moduli results in the appearance of picture-changing operators for the b-c fermionic ghosts with the ghost number -1. Important example of the b-c ghost pictures involves the vertex operators in integrated and unintegrated forms. We obtain the BRST-invariant expressions for the b-c picture-changing operators for open and closed strings and study some of their properties. We also show that the superconformal moduli spaces of the NSR theory contain the global singularities, leading to the phenomenon of ghost-matter mixing and the appearance of nonperturbative D-brane creation operators.

We observe and study new nonlinear global space–time symmetries of the full ghost + matter action of RNS superstring theory. We show that these surprising new symmetries are generated by the special worldsheet currents (physical vertex operators) of RNS superstring theory, violating the equivalence of superconformal ghost pictures. We review the questions of BRST-invariance and nontriviality of picture-dependent vertex operators and show their relation to hidden space–time symmetries and hidden space–time dimensions. In particular, we relate the space–time transformations, induced by picture-dependent currents, to the symmetries observed in the 2T physics approach.