An ansatz for a non-perturbative four-graviton amplitude in type IIB superstring theory

TL;DR

This paper proposes a non-perturbative four-graviton amplitude in type IIB superstring theory, incorporating SL(2,Z) invariance, perturbative, and non-perturbative D-instanton effects, matching known limits and particle spectra.

Contribution

It introduces a novel SL(2,Z) invariant amplitude that unifies perturbative and non-perturbative contributions in type IIB superstring theory.

Findings

Amplitude includes perturbative and D-instanton effects.

Singularities correspond to $(p,q)$ string states.

Structure of perturbative corrections to the effective action.

Abstract

A natural SL(2,Z) invariant generalization of the Veneziano amplitude in type IIB superstring theory is investigated. It includes certain perturbative and non-perturbative (D-instanton) contributions, and it reduces to the correct expressions in different limits. The singularities are poles in the $s$-$t$-$u$ channels, corresponding to the exchange of particles with a mass spectrum coinciding with that of $(p,q)$ string states. We describe the general structure of the associated perturbative corrections to the effective action.