Non-Universal Anomalies in Heterotic String Constructions

TL;DR

This paper explores anomalies in heterotic orbifolds and their blowups, revealing that axionic couplings are generally non-universal, which impacts the understanding of anomaly cancellation and discrete symmetries in string theory.

Contribution

It demonstrates that anomaly cancellation via axions in heterotic orbifolds is typically non-universal, clarifying recent misconceptions and analyzing implications for discrete symmetries on Calabi-Yau manifolds.

Findings

Anomalous U(1) symmetries are canceled by non-universal axions.

Non-universality of axionic couplings is common outside orbifolds.

Implications for discrete R symmetries are discussed.

Abstract

We investigate anomalies on heterotic orbifolds and their blowups. We give a simple example of an orbifold blowup which contains anomalous U(1) symmetries that are canceled by axions which couple non-universally to the different gauge groups, thus clarifying some confusion which recently arose in the literature concerning anomaly universality. We argue that non-universal axionic couplings are the general case, and that the couplings are only universal in the case of orbifolds. We comment on the consequences of this non-universality for discrete R symmetries. We furthermore investigate the origin of discrete (R and non-R) symmetries on smooth Calabi-Yau manifolds.