On 4/24/13 4/24/13 10:33 AM, Wade Jenkins wrote: > Tom Roberts wrote: >>>> Hmmmm. In physics, where we always have an ORIENTABLE manifold WITH >>>> METRIC, >>> >>> Certainly at an undergraduate level, but once you get into things like >>> gauge theories you need manifolds without a metric. >> >> Yes. I meant spacetime manifold. > > Finally you admit, relativity is an undergraduate level!
But GR and gauge theories not, and the issues discussed here are not (except possibly for a very advanced undergraduate).