S-Duality as an Open String Gauge Symmetry

Abstract

The paper discusses the connection between S-duality and string-theoretic picture-changing formalism. The singular limit of the picture-changing transformation at zero momentum leads to the presence of the topological 5-form charge in the type IIB superalgebra which is attributed to the M5-brane. The topological charge defines the boundary D-brane state, which also is the analogue of the monopole part of the Olive-Witten's result in field theory.The correlation functions involving this non-perturbative state are computed.The non-perturbative D-brane states are associated with the ghost number cohomologies, introduced in the paper. Connections with M(atrix) theory are discussed.

16 pages, TeX. The computational error of the previous version is corrected; erratum added. The new derivation of the central terms in the superalgebra is presented and new physical motivation is given