String instantons, fluxes and moduli stabilization

TL;DR

This paper explores dual heterotic and type I string models with orbifold compactifications, demonstrating how instanton effects and fluxes can stabilize moduli fields and the dilaton in a racetrack scenario.

Contribution

It introduces a method to compute non-perturbative gauge coupling corrections using duality and applies fluxes and instantons to achieve moduli stabilization in type I models.

Findings

Non-perturbative corrections can be calculated via heterotic perturbative methods.

Fluxes and instantons effectively stabilize most moduli fields.

A racetrack model stabilizes the dilaton and other moduli.

Abstract

We analyze a class of dual pairs of heterotic and type I models based on freely-acting $\mathbb{Z}_2 \times \mathbb{Z}_2$ orbifolds in four dimensions. Using the adiabatic argument, it is possible to calculate non-perturbative contributions to the gauge coupling threshold corrections on the type I side by exploiting perturbative calculations on the heterotic side, without the drawbacks due to twisted moduli. The instanton effects can then be combined with closed-string fluxes to stabilize most of the moduli fields of the internal manifold, and also the dilaton, in a racetrack realization of the type I model.