Abstract:
We discuss an approach to compute two-particle scattering amplitudes for spinless light
particles colliding at Planckian centre-of-mass energies, with increasing momentum transfer away
from the eikonal limit. The leading corrections to the eikonal amplitude, in our 'external metric'
approach, are shown to be vanishingly small in the limit of the source particle mass going to zero.
For massless charged particles, the electromagnetic and gravitational interactions decouple in the
eikonal limit, hut mix non-trivially for the leading order corrections.