– Campus Golm, Haus 9, Raum 0.17 (und online)
Sandpile models and spanning trees
Wioletta Ruszel (Univ. Utrecht)
Sylvie Paycha (Potsdam University)
Two essential ingredients in classical gauge field theory are gauge fields given by connections on a principal bundle and gauge transformations given by automorphisms of the bundle.
Principal bundles are in one to one correspondence with gauge groupoids and connections on principal bundles amount to infinitesimal connections on their corresponding gauge groupoid. We study gauge groupoids equipped with direct connections, which one can roughly view as enhanced infinitesimal connections in so far as they can be built from a torsion free connection on the underlying manifold combined with an infinitesimal connection.
Direct connections occur in various disguises in the mathematical literature, and specifically in Hairer's regularity structures where they are called re-expansion maps.
Gauge groupoids behave functorially under jet prolongation, a useful fact to have in mind in the context of regularity structures. We shall argue that this functoriality carries out to flat direct connections when the underlying manifold is affine.
Gauge transformations of a principal bundle induce transformations of the corresponding gauge groupoid, which for short, we call gaugeoid transformations. Not all gaugeoid transformations come from a gauge transformation, which gives rise to interesting cohomological obstructions and led us to investigating higher analogues of gauge groupoids and their transformations.
This is based on ongoing joint work with S. Azzali and A. Frabetti together with Y. Boutaib and A. Garmendia.
Meeting ID: 498 775 1829