Pseudo-anomalous U(1) symmetry in the strong coupling limit of the heterotic string

TL;DR

This paper explores the emergence of anomalous U(1)_X symmetries in strongly coupled heterotic string theory, analyzing their anomalies and Fayet-Iliopoulos terms in the presence of five-branes, revealing differences from the weakly coupled scenario.

Contribution

It provides a nonperturbative analysis of anomalous U(1) symmetries and Fayet-Iliopoulos terms in the strongly coupled heterotic string framework with five-branes.

Findings

Anomalous U(1)_X symmetries originate nonperturbatively in the strongly coupled regime.

Fayet-Iliopoulos terms are computed and found to be lower than in the weakly coupled case.

The presence of five-branes influences anomaly cancellation and gauge symmetry structure.

Abstract

We discuss, in the context of the strongly coupled E_8 \times E_8 heterotic string proposed by Horava and Witten, the appearance of anomalous U(1)_X symmetries of a nonperturbative origin, related to the presence, after compactification, of five-branes in the five-dimensional bulk of the theory. We compute the gauge anomalies and the induced Fayet-Iliopoulos terms on each boundary, which we find to be lower than the universal one induced in the weakly coupled case.