Non-Abelian Gerbes from Strings on a Branched Space-Time

Abstract

As superstring solitons that carry Neuveu-Schwarz charge can be described in terms of gerbes, one expects non-Abelian gerbes to appear e.g. in the exotic six-dimensional world-volume theories of coinciding NS5 branes. We consider open bosonic strings on a space-time that is branched in such a way that the B-field is provided with the same Lie algebra structure as the world-volume gauge field on a D-brane. These considerations motivate a generalization of the cocycle conditions and the transformation rules of an Abelian gerbe in hypercohomology. The resulting system incorporates in a natural way the NS two-form, the RR gauge field, the Chan-Paton gauge field, the relevant gauge transformations and the holonomies associated to Wilson surface observables.