Threshold corrections in orbifold models and superstring unification of gauge interactions

TL;DR

This paper analyzes one-loop string threshold corrections in orbifold models, exploring their impact on gauge coupling unification considering moduli effects, embeddings, Wilson lines, and anomalous U(1) thresholds.

Contribution

It provides a detailed numerical evaluation of moduli-independent threshold corrections and examines gauge unification scenarios with various model features.

Findings

Threshold corrections depend on model specifics and can match low-energy data.

Unification can be achieved with appropriate moduli and threshold adjustments.

Inclusion of anomalous U(1) thresholds influences unification scales.

Abstract

The string one loop renormalization of the gauge coupling constants is examined in abelian orbifold models. The contributions to string threshold corrections independent of the compactification moduli fields are evaluated numerically for several representative examples of orbifold models. We consider cases with standard and non-standard embeddings as well as cases with discrete Wilson lines background fields which match reasonably well with low energy phenomenology. We examine one loop gauge coupling constants unification in a description incorporating the combined effects of moduli dependent and independent threshold corrections, an adjustable Kac-Moody level for the hypercharge group factor and a large mass threshold associated with an anomalous $U(1)$ mechanism.