Gravitational monopoles, anomalies and M$E_8$ bundles

Abstract

In this paper we try to clarify the physical meaning of the gauge theory that underlies the K-theoretical classification of RR charges in type IIA. Our main tool are the conditions for the cancellation of the Freed-Witten global anomaly when we take into account the effects of a flat and a general B-field. In each case we will see how K-theory captures some eleven dimensional information. In the first case and studying the electric properties of the D6-brane we see an eleven dimensional U(2) gauge symmetry, while the second can be related to an $E_8$ theory. Moreover, in the reduction from the general to the flat case, we find that the Romans' mass gives the number of unstable intial D9-branes.