Generalised universality of gauge thresholds in heterotic vacua with and without supersymmetry

TL;DR

This paper investigates one-loop gauge coupling corrections in heterotic string vacua, revealing conditions under which universal threshold behaviors persist even with broken supersymmetry, supported by various examples.

Contribution

It identifies specific conditions for universal gauge threshold differences in non-supersymmetric heterotic vacua, extending the concept of universality beyond supersymmetric cases.

Findings

Universal threshold differences can occur in non-supersymmetric models.

Conditions for supersymmetry breaking that preserve universality are formulated.

Examples include non-supersymmetric chiral models in four dimensions.

Abstract

We study one-loop quantum corrections to gauge couplings in heterotic vacua with spontaneous supersymmetry breaking. Although in non-supersymmetric constructions these corrections are not protected and are typically model dependent, we show how a universal behaviour of threshold differences, typical of supersymmetric vacua, may still persist. We formulate specific conditions on the way supersymmetry should be broken for this to occur. Our analysis implies a generalised notion of threshold universality even in the case of unbroken supersymmetry, whenever extra charged massless states appear at enhancement points in the bulk of moduli space. Several examples with universality, including non-supersymmetric chiral models in four dimensions, are presented.