Zp charged branes in flux compactifications

TL;DR

This paper classifies Z_p discrete gauge symmetries and charges arising from wrapped branes in flux compactifications, revealing their realization via fluxes, anomalies, and dualities, and exploring their mathematical structure.

Contribution

It provides a detailed classification of Z_p charges and symmetries in flux compactifications, including non-Abelian cases and their relation to torsion (co)homology and generalized K-theory.

Findings

Z_p-valued particles, strings, and domain walls are linked to discrete gauge symmetries.

Discrete symmetries are realized as subgroups of broken U(1) symmetries via flux couplings.

Examples include non-Abelian discrete gauge groups and relations to T-duality and torsion (co)homology.

Abstract

We consider 4d string compactifications in the presence of fluxes, and classify particles, strings and domain walls arising from wrapped branes which have charges conserved modulo an integer p, and whose annihilation is catalized by fluxes, through the Freed-Witten anomaly or its dual versions. The Z_p-valued strings and particles are associated to Z_p discrete gauge symmetries, which we show are realized as discrete subgroups of 4d U(1) symmetries broken by their Chern-Simons couplings to the background fluxes. We also describe examples where the discrete gauge symmetry group is actually non-Abelian. The Z_p-valued domain walls separate vacua which have different flux quanta, yet are actually equivalent by an integer shift of axion fields (or further string duality symmetries). We argue that certain examples are related by T-duality to the realization of discrete gauge symmetries and Z_p charges from torsion (co)homology. At a formal level, the groups classifying these discrete charges should correspond to a generalization of K-theory in the presence of general fluxes (and including fundamental strings and NS5-branes).