2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184329We present an M-theory proof of the anomaly of Freed and Witten which in general shifts the quantisation law for the U(1) gauge field on a D6-brane. The derivation requires an understanding of how fields on the D6-brane lift to M-theory, together with a localisation formula which we prove using a U(1)-index theorem. We also show how the anomaly is related to the K-theory classification of Ramond-Ramond fields. In addition we discuss the M-theory origin of the D6-brane effective action, and illustrate the general arguments with a concrete example.25 pages; v2: minor alterations, references added; v3: various arguments clarified, mathematical background added. Published versionHigh Energy Physics - Theorytext