Form-field gauge symmetry in M-theory

We show how to cast an interacting system of M‐branes into manifestly gauge‐invariant form using an arrangement of higher‐dimensional Dirac surfaces. Classical M‐theory has a cohomologically nontrivial and noncommutative set of gauge symmetries when written using a “doubled” formalism containing 3‐form and 6‐form gauge fields. We show how the arrangement of Dirac surfaces allows an integral subgroup of these symmetries to be preserved at the quantum level. The proper context for discussing these large gauge transformations is relative cohomology, in which the 3‐form transformation parameters become exact when restricted to the five‐brane worldvolume. This structure yields the correct lattice of M‐theory brane charges.