Flux Stabilization of D-branes

TL;DR

The paper shows that D-branes wrapped on S^2 in SU(2) group manifolds are stabilized by quantized worldvolume flux, with a Born-Infeld analysis reproducing exact SU(2) WZW CFT results (including the k→k+2 shift) for brane masses, spectra, and fluctuations. It establishes a precise correspondence between semiclassical brane configurations and Cardy boundary states, and extends the flux-stabilization mechanism to general simple groups via twined conjugacy classes. A paradox about non-quantized RR charges is addressed through near-horizon massive RR fields and CS couplings, with discussions of possible connections to holographic duals. The results provide a robust, cross-validated picture of D-brane stability in curved group manifolds and their CFT descriptions.

Abstract

We explain how D-branes on group manifolds are stabilized against shrinking by quantized worldvolume U(1) fluxes. Starting from the Born-Infeld action in the case of the SU(2) group manifold we derive the masses, multiplicities and spectrum of small fluctuations of these branes, and show that they agree exactly with the predictions of conformal field theory, to all orders in the $α^\prime$ expansion. We discuss the generalization to other groups and comment on an apparent paradox: why are the `RR charges' of these branes not quantized?