Complete Bundle Moduli Reduction in Heterotic String Compactifications

TL;DR

This paper presents a method to reduce the number of vector bundle moduli in heterotic string compactifications, enabling the construction of rigid bundles with superpotentials depending only on complex structure moduli, thus aiding moduli stabilization.

Contribution

It explicitly classifies twists that reduce bundle moduli and provides a formula for the reduction in SU(5) bundles, achieving complete rigidity in some cases.

Findings

Explicit reduction formula for bundle moduli in SU(5) bundles.

Construction of rigid bundles with superpotentials depending solely on complex structure.

Examples demonstrating complete moduli reduction leading to rigid bundles.

Abstract

A major problem in discussing heterotic string models is the stabilisation of the many vector bundle moduli via the superpotential generated by world-sheet instantons. In arXiv:1110.6315 we have discussed the method to make a discrete twist in a large and much discussed class of vector bundles such that the generation number gets new contributions (which can be tuned suitably) and at the same time the space of bundle moduli of the new, twisted bundle is a proper subspace (where the 'new', non-generic twist class exists) of the original bundle moduli space; one thus gets a model, closely related to the original model one started with, but with enhanced flexibility in the generation number and where on the other hand the number of bundle moduli is {\em somewhat} reduced. Whereas in the previous paper the emphasis was on examples for the new flexibility in the generation number we here classify and describe explicitly the twists and give the precise reduction formula (for the number of moduli) for SU(5) bundles leading to an SU(5) GUT group in four dimensions. Finally we give various examples where the bundle moduli space is reduced {\em completely}: the superpotential for such {\em rigid} bundles becomes a function of the complex structure moduli alone (besides the exponential Kahler moduli contribution).