String-theoretic unitary S-matrix at the threshold of black-hole production

Abstract

Previous results on trans-Planckian collisions in superstring theory are rewritten in terms of an explicitly unitary S-matrix whose range of validity covers a large region of the energy/impact-parameter plane. Amusingly, as part of this region's border is approached, properties of the final state start resembling those expected from the evaporation of a black-hole even well below its production threshold. More specifically, we conjecture that, in an energy window extending up such a threshold, inclusive cross sections satisfy a peculiar "anti-scaling" behaviour seemingly preparing for a smooth transition to black-hole physics.