Interacting fermionic and pomeronic strings: Gravitational interaction of the Ramond fermion

Abstract

We present a ghost-free model for the Ramond fermion interacting with closed and open bosonic strings. Since a closed string contains a «graviton» state as a physical state, which reduces to the Einstein graviton in the zero-slope limit, we introduce the interaction of the closed-string graviton with the fermionic string of Ramond in a way analogous to the usual tetrad formalism for the interacting gravitational and spinor fields. By considering the general co-ordinate transformation and the local Lorentz transformation for the fermionic string, we obtain the vertex for an external tetrad field. We show that the vertex satisfies desirable gravitational and supergauge properties. A general form of the vertices describing the emission of the closed string out of the fermionic string is given by extracting the gauge properties of the graviton vertex. In our model, the self-interaction among the closed strings is described by the nonplanar version of the Neveu-Schwarz model. The zero-slope limit of our model is also briefly considered.