Vertex Operators, String Vertices and Conformal Field Theory Deformations

Abstract: We compute multi-string interaction vertices by sewing of basic string interaction vertex operators, so called dual Reggeon vertex operators. These operators describe the interaction between two complete external string sectors. They are particularly useful when the interactions involve twisted sectors. In paper I we check the dual vertex formalism by sewing multi-loop interactions in the bosonic string. We also construct the dual Reggeon vertex describing the interaction between a twisted and an untwisted bosonic string sektor. In papers II to IV we compute the string interaction vertex describing the interaction between two twisted fermion sectors of the RNS string.

Nearby conformal field theories can be connected by so called marginal deformations. Papers V and VI deal with the regularization of such marginal deformations and the construction of connections on spaces of conformal field theories.

The papers I to VI concern various aspects of string field theory. Sewing of Reggeon vertex operators may be thought of as interactions between second quantized strings fields. The spaces of conformal field theories may be thought of as the spaces of classical solutions to a string field action. In the introductory text we therefore provide some background material on conformal field theory and string field theory.