String vacua with flux from freely-acting obifolds

TL;DR

This paper establishes a precise T-duality correspondence between freely-acting orbifolds and string vacua with NSNS flux, analyzing a specific non-compact heterotic orbifold with N=2 SUSY and its non-Kahler T-dual geometry.

Contribution

It demonstrates the detailed geometric and physical properties of the T-dual flux background, highlighting the role of torsion and the limitations of current T-duality rules in heterotic string theory.

Findings

The T-dual background is non-Kahler with generic torsion compatible with SUSY.

All equations of motion are satisfied except the Bianchi identity, which holds only at leading order.

The discrepancy is due to unknown higher-order corrections to heterotic T-duality rules.

Abstract

A precise correspondence between freely-acting orbifolds (Scherk-Schwarz compactifications) and string vacua with NSNS flux turned on is established using T-duality. We focus our attention to a certain non-compact Z_2 heterotic freely-acting orbifold with N=2 supersymmetry (SUSY). The geometric properties of the T-dual background are studied. As expected, the space is non-Kahler with the most generic torsion compatible with SUSY. All equations of motion are satisfied, except the Bianchi identity for the NSNS field, that is satisfied only at leading order in derivatives, i.e. without the curvature term. We point out that this is due to unknown corrections to the standard heterotic T-duality rules.