ncts

I discuss my latest preprint about gauge theories based on principal bundles $\mathcal{P}$ equipped with a right $\mathcal{G}$ -action, where $\mathcal{G}$ is a Lie group bundle instead of a Lie group. Due to the fact that a $\mathcal{G}$ -action acts fibre by fibre, pushforwards of tangent vectors via a right-translation act now only on the vertical structure of $\mathcal{P}$ . Thus, we generalize pushforwards using sections of $\mathcal{G}$ , and in order to provide a definition independent of the choice of section we fix a connection on $\mathcal{G}$ , which will modify the pushforward by subtracting the fundamental vector field generated by a generalized Darboux derivative of the chosen section. A horizontal distribution on $\mathcal{P}$ invariant under such a modified pushforward leads to a parallel transport on $\mathcal{P}$ which is a homomorphism w.r.t.\ the $\mathcal{G}$ -action and the parallel transport on $\mathcal{G}$ . For achieving gauge invariance we impose conditions on the connection 1-form $\mu$ on $\mathcal{G}$ : $\mu$ has to be a multiplicative form, \textit{i.e.}\ closed w.r.t.\ a certain simplicial differential $\delta$ on $\mathcal{G}$ , and the curvature $R_\delta$ of $\mu$ has to be $\delta$ -exact with primitive $\zeta$ ; $\mu$ will be the generalization of the Maurer-Cartan form of the classical gauge theory, while the $\delta$ -exactness of $R_\delta$ will generalize the role of the Maurer-Cartan equation. For allowing curved connections on $\mathcal{G}$ we will need to generalize the typical definition of the curvature/field strength $F$ on $\mathcal{P}$ by adding $\zeta$ to $F$

This leads to a generalized gauge theory with many similar, but generalized, statements, including Bianchi identity, gauge transformations and Darboux derivatives. An example for a gauge theory with a curved Maurer-Cartan form $\mu$ will be provided by the inner group bundle of the Hopf fibration $\mathit{S}^7$ $\to\$ $\mathit{S}^4$ .