Topology Change from (Heterotic) Narain T-Duality

TL;DR

This paper investigates how Narain T-duality induces topology changes in string backgrounds with nontrivial fluxes, preserving key physical conditions and exchanging geometric and gauge properties.

Contribution

It characterizes the action of Narain T-duality on topology and flux in nontrivially fibered string backgrounds, including supersymmetric cases with flux and gauge symmetry exchanges.

Findings

Topology change preserves tadpole conditions.

T-duality exchanges flux with curvature of circle fibrations.

Supersymmetry conditions are exchanged between circle and gauge bundles.

Abstract

We consider Narain T-duality on a nontrivially fibered n-torus bundle in the presence of a topologically nontrivial NS H flux. The action of the duality group on the topology and H flux of the corresponding type II and heterotic string backgrounds is determined. The topology change is specialized to the case of supersymmetric T^2-fibered torsional string backgrounds with nontrivial H flux. We prove that it preserves the global tadpole condition in the total space as well as on the base of the torus fibration. We find that some of these T-dualities exchange half of the field strength of an unbroken U(1) gauge symmetry with the anti-selfdual part of the curvature of a physical circle fibration. We verify that such T-dualities indeed exchange the supersymmetry condition for the circle bundle with that of the gauge bundle.