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APS » Journals » Phys. Rev. Lett. » Volume 98 » Issue 16
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Phys. Rev. Lett. 98, 161303 (2007) [4 pages]

Cancellations Beyond Finiteness in N=8 Supergravity at Three Loops

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Z. Bern1, J. J. Carrasco1, L. J. Dixon2, H. Johansson1, D. A. Kosower3,4, and R. Roiban5
1Department of Physics and Astronomy, UCLA, Los Angeles, California 90095-1547, USA
2Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309, USA
3Service de Physique Théorique, CEA-Saclay, F-91191 Gif-sur-Yvette cedex, France
4Institut für Theoretische Physik, Universität Zürich, CH-8057 Zürich, Switzerland
5Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA

Received 19 February 2007; published 19 April 2007

We construct the three-loop four-point amplitude of N=8 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 D dimensions no worse than that of N=4 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 N=8 supergravity may be a perturbatively finite theory of quantum gravity.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.98.161303
DOI:
10.1103/PhysRevLett.98.161303
PACS:
04.65.+e, 11.15.Bt, 11.25.Db, 12.60.Jv
 
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