  Aspects of super-planckian gravitational scattering and black hole formation
are investigated, largely via a partial-wave representation. At large and
decreasing impact parameters, amplitudes are expected to be governed by single
graviton exchange, and then by eikonalized graviton exchange, for which
partial-wave amplitudes are derived. In the near-Schwarzschild regime,
perturbation theory fails. However, general features of gravitational
scattering associated with black hole formation suggest a particular form for
amplitudes, which we express as a black hole ansatz. We explore features of
this ansatz, including its locality properties. These amplitudes satisfy
neither the Froissart bound, nor apparently the more fundamental property of
polynomial boundedness, through which locality is often encoded in an S-matrix
framework. Nevertheless, these amplitudes do satisfy a macroscopic form of
causality, expressed as a polynomial bound for the forward-scattering
amplitude.
