THE ULTRARELATIVISTIC LIMIT OF THE BOOSTED KERR-NEWMAN GEOMETRY AND THE SCATTERING OF SPIN-1/2 PARTICLES

The ultrarelativistic limit of the Kerr-Newman geometry is studied in detail. We find the corresponding gravitational shock-wave background associated with this limit. Interestingly, this allows us to find the source of the Kerr-Newman geometry in the ultrarelativistic regime. We study the scattering of spin-1/2 fields in the gravitational shock-wave geometries, and discuss the presence of the poles iGs = n = 0, 1, 2,..., already present in the case of scalar fields in the Aichelburg-Sexl metric. We compare this with the scattering by ultrarelativistic extended sources for which such poles do not appear, and with the scattering of fundamental strings.