Let GG be a (maybe Lie) group, and M a space (perhaps a manifold). Then a principal G-bundle over M is a bundle PtoM on which G acts (by fiber-preserving maps), so that each fiber is a G-torsor (a G-action isomorphic, although not canonically so, to the action of G on itself by multiplication). A map of G-bundles is a bundle map that plays well with the actions.
Then I more-or-less know what the classifying space of G is: it's some bundle EGtoBG that's universal in the homotopy category of (principal) G-bundles. I.e. any G-bundle PtoM has a (unique up to homotopy) map PtoEG and MtoBG, and conversely any map MtoBG (up to homotopy) determines a (unique up to isomorphism) bundle PtoM and by pulling back the obvious square.
At least this is how I think it works. Wikipedia's description of BG is here.
So, let G be a Lie group and M a smooth manifold. On a G-bundle PtoM I can think about connections. As always, a connection should determine for each smooth path in M a G-torsor isomorphism between the fibers over the ends of the path. So in particular, a bundle-with-connection is a (smooth) functor from the path space of M to the category of G-torsors. But not all of these are connections: the value of holonomy along a path is an invariant up to "thin homotopy", which is essentailly homotopy that does not push away from the image of the curve. So one could say that a bundle-with-connection is a smooth functor from the thin-homotopy-path-space.
More hands-on, a connection on PtoG is a rmLie(G)-valued one-form on P that is (1) invariant under the G action, and (2) restricts on each fiber to the canonical rmLie(G)-valued one-form on G that takes a tangent vector to its left-invariant field (thought of as an element of rmLie(G)).
Anyway, my question is: is there a "space" (of some sort) that classifies G-bundles over M with connections? By which I mean, the data of such a bundle should be the same (up to ...) as a map Mto this space. The category of G-torsors is almost right, but then the map comes not from M but from its thin-homotopy path space.
Please re-tag as desired.
No comments:
Post a Comment