Abstract
We construct the three-loop four-point amplitude of supergravity using the unitarity method. The amplitude is ultraviolet finite in four dimensions. Novel cancellations, not predicted by traditional superspace power-counting arguments, render its degree of divergence in dimensions no worse than that of super-Yang-Mills theory—a finite theory in four dimensions. Similar cancellations can be identified at all loop orders in certain unitarity cuts, suggesting that supergravity may be a perturbatively finite theory of quantum gravity.
- Received 19 February 2007
DOI:https://doi.org/10.1103/PhysRevLett.98.161303
©2007 American Physical Society