Universality properties of N=2 and N=1 Heterotic threshold corrections

TL;DR

This paper investigates one-loop gauge coupling corrections in heterotic string compactifications, revealing universal properties in N=2 models and analyzing their impact on gauge unification in N=1 models.

Contribution

It provides explicit formulas for gauge thresholds in N=2 heterotic models and explores their implications for gauge unification in N=1 models.

Findings

Threshold corrections are universal within certain N=2 models.

N=1 sector contributions can significantly modify unification predictions.

Explicit calculations demonstrate the impact on string unification scenarios.

Abstract

In the framework of heterotic compactifications, we consider the one-loop corrections to the gauge couplings, which were shown to be free of any infra-red ambiguity. For a class of N=2 models, namely those that are obtained by toroidal compactification to four dimensions of generic six-dimensional N=1 ground states, we give an explicit formula for the gauge-group independent thresholds, and show that these are equal within this class, as a consequence of an anomaly-cancellation constraint in six dimensions. We further use these results to compute the (N=2)-sector contributions to the thresholds of N=1 orbifolds. We then consider the full contribution of N=1 sectors to the gauge couplings which generically are expected to modify the unification picture. We compute such corrections in several models. We finally comment on the effect of such contributions to the issue of string unification.