Green-Schwarz mechanism in heterotic (2,0) gauged linear sigma models: torsion and NS5 branes
Michael Blaszczyk, Stefan Groot Nibbelink, Fabian Ruehle
Journal of High Energy Physics
Heterotic string compactifications can be conveniently described in the language of (2,0) gauged linear sigma models (GLSMs). Such models allow for Fayet-Iliopoulos (FI)-terms, which can be interpreted as Kahler parameters and axions on the target space geometry. We show that field dependent non-gauge invariant FI-terms lead to a Green-Schwarz-like mechanism on the worldsheet which can be used to cancel worldsheet anomalies. However, given that these FI-terms are constrained by quantization
... itions due to worldsheet gauge instantons, the anomaly conditions turn out to be still rather constraining. Field dependent non-gauge invariant FI-terms result in non-Kahler, i.e. torsional, target spaces in general. When FI-terms involve logarithmic terms, the GLSM seems to describe the heterotic string in the presence of Neveu-Schwarz (NS)5 branes. In particular, when the gauge bundle overcloses the Bianchi identities, the GLSM describes a decompactified target space geometry due to anti-NS5 branes.