Nonperturbative corrections to 4D string theory effective actions from SL(2,Z) duality and supersymmetry

TL;DR

This paper computes nonperturbative D-brane instanton effects in type IIB string theory compactified on Calabi-Yau threefolds, integrating them with known corrections into a modular invariant function that shapes the low-energy effective action.

Contribution

It introduces a unified framework incorporating D-instanton contributions with perturbative and worldsheet corrections using SL(2,Z) duality and supersymmetry.

Findings

Derived explicit D(-1) and D1-brane instanton contributions.

Constructed a modular invariant function for the hypermultiplet moduli space.

Enhanced understanding of nonperturbative effects in string compactifications.

Abstract

We find the D(-1) and D1-brane instanton contributions to the hypermultiplet moduli space of type IIB string compactifications on Calabi-Yau threefolds. These combine with known perturbative and worldsheet instanton corrections into a single modular invariant function that determines the hypermultiplet low-energy effective acction.