New expressions for gravitational scattering amplitudes
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- Hodges, A. J. High Energ. Phys. (2013) 2013: 75. doi:10.1007/JHEP07(2013)075
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New methods are introduced for evaluating tree-level gravitational scattering amplitudes. A new N=7 super-symmetric recursion yields amplitudes free from the spurious double poles of the N=8 theory. This is illustrated by a new nine-term expression for the six-graviton NMHV amplitude. The general scheme also implies a simplified recurrence relation for MHV amplitudes. We show how this relation is satisfied by a new expression for MHV amplitudes, far simpler than those hitherto identified, and exhibiting manifest Sn symmetry. This reformulation is related to a new momentum-twistor representation of the MHV amplitudes.