- #1
IRobot
- 87
- 0
I heard in a conference that gravity forbids to construct local gauge invariants like [itex]Tr-\frac14 F^{\mu\nu}_aF_{\mu\nu}^a[/itex] and only allows non-local gauge invariant quantities like Wilson Loops: [itex]Tr P e^{\oint_{\gamma} A_a dx^a}[/itex]. Could someone explain me where does it come from? I have a basis knowledge of QFT and GR. If you could had a reference it would be great!