Chern-Simons foam
arXiv:0810.3041
Abstract
Chern-Simons theory can be defined on a cell complex, such as a network of bubbles, which is not a (Hausdorff) manifold. Requiring gauge invariance determines the action, including interaction terms at the intersections, and imposes a relation between the coupling constants of the CS terms on adjacent cell walls. We also find simple conservation laws for charges at the intersections.
22 pages, 3 figures, version 2: acknowledgement added, minor typos corrected