Fivebrane Instanton Corrections to the Universal Hypermultiplet

TL;DR

This paper studies fivebrane instanton effects in type IIA string theory compactified on Calabi-Yau threefolds, revealing nonperturbative corrections to the universal hypermultiplet moduli space, especially affecting the Ramond-Ramond sector.

Contribution

It provides a detailed analysis of fivebrane instantons, including zero modes and instanton measure, and computes their nonperturbative effects on the hypermultiplet moduli space.

Findings

Only the Ramond-Ramond sector receives instanton corrections.

Instantons break certain isometries of the moduli space.

Explicit instanton measure and zero modes are determined.

Abstract

We analyze the Neveu-Schwarz fivebrane instanton in type IIA string theory compactifications on rigid Calabi-Yau threefolds, in the low-energy supergravity approximation. It there appears as a finite action solution to the Euclidean equations of motion of a double-tensor multiplet (dual to the universal hypermultiplet) coupled to N=2, D=4 supergravity. We determine the bosonic and fermionic zero modes, and the single-centered instanton measure on the moduli space of collective coordinates. The results are then used to compute, in the semiclassical approximation, correlation functions that nonperturbatively correct the universal hypermultiplet moduli space geometry of the low-energy effective action. We find that only the Ramond-Ramond sector receives corrections, and we discuss the breaking of isometries due to instantons.