Solving the Decompactification Problem in String Theory

TL;DR

This paper analyzes heterotic string models where supersymmetry is spontaneously broken and demonstrates a mechanism that suppresses threshold corrections in the decompactification limit, addressing the decompactification problem in string theory.

Contribution

It introduces a mechanism that suppresses gauge coupling threshold corrections in decompactification limits, providing a solution to the decompactification problem in string models with broken supersymmetry.

Findings

Threshold corrections are suppressed as supersymmetry is restored at decompactification.

Standard N=2 models exhibit coupling blow-up with volume, unlike the studied models.

Mechanism can be adapted for models with lower supersymmetry.

Abstract

We investigate heterotic ground states in four dimensions in which N=4 supersymmetry is spontaneously broken to N=2. N=4 supersymmetry is restored at a decompactification limit corresponding to $m_{3/2}\to 0$. We calculate the full moduli dependent threshold corrections and confirm that they are supressed in the decompactification limit $m_{3/2}\to 0$ as expected from the restoration of N=4 supersymmetry. This should be contrasted with the behavior of the standard N=2 groundstates where the coupling blow up linearly with the volume of the decompactifying manifold. This mechanism provides a solution to the decompactification problem for the gauge coupling constants. We also discuss how the mechanism can be implemented in ground states with lower supersymmetry.