Stringy instanton corrections to N=2 gauge couplings

TL;DR

This paper investigates how stringy instantons contribute to N=2 gauge couplings in a specific string theory model, providing explicit calculations and confirming duality predictions with heterotic string theory.

Contribution

It presents a detailed calculation of stringy instanton effects on gauge couplings in an N=2 model, validating the approach through duality with heterotic string theory.

Findings

Explicit evaluation of stringy instanton contributions to gauge kinetic functions.

Matching of instanton effects with heterotic 1-loop threshold computations.

Validation of the instanton calculus via duality correspondence.

Abstract

We discuss a string model where a conformal four-dimensional N=2 gauge theory receives corrections to its gauge kinetic functions from "stringy" instantons. These contributions are explicitly evaluated by exploiting the localization properties of the integral over the stringy instanton moduli space. The model we consider corresponds to a setup with D7/D3-branes in type I' theory compactified on T4/Z2 x T2, and possesses a perturbatively computable heterotic dual. In the heteoric side the corrections to the quadratic gauge couplings are provided by a 1-loop threshold computation and, under the duality map, match precisely the first few stringy instanton effects in the type I' setup. This agreement represents a very non-trivial test of our approach to the exotic instanton calculus.