Three Graviton Scattering in M-Theory

The leading eikonal S-matrix for three graviton scattering in d=11 supergravity and Matrix Theory are shown to precisely agree. The result unifies the source-probe plus recoil approach of Okawa and Yoneya and relaxes the restriction imposed by those authors that all D-particle impact parameters and velocities are mutually perpendicular. Furthermore, the unified S-matrix approach facilitates a clean-cut study of M-theoretic R^4 curvature corrections to the low energy supergravity effective action. In particular, the leading R^4 correction to the three graviton S-matrix is computed and compared to the corresponding next to leading order two loop U(3) amplitude in Matrix Theory. We find a clear disagreement of the two resulting tensor structures.