D-branes, B-fields and twisted K-theory
P. Bouwknegt and V. Mathai
ADP-00-07/M88, hep-th/0002023, J. High Energy Phys. 03 (2000) 007.

In this note we propose that D-brane charges, in the presence of a topologically non-trivial B-field, are classified by the K-theory of an infinite dimensional C^*-algebra. In the case of B-fields whose curvature is pure torsion our description is shown to coincide with that of Witten.

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