Gravitational effects in ultrahigh-energy string scattering

TL;DR

This paper explores the interplay of string and gravitational effects in ultrahigh-energy string scattering, revealing that gravitational processes dominate at small impact parameters and challenging local theory bounds.

Contribution

It provides new insights into the dominance of gravitational effects over string excitations in black hole formation at ultrahigh energies.

Findings

Gravitational effects dominate at small impact parameters.

String excitations do not directly cause black hole formation.

High-energy amplitudes violate local theory bounds.

Abstract

Ultrahigh-energy string scattering is investigated to clarify the relative role of string and gravitational effects, and their possible contributions to nonlocal behavior. Different regimes can be characterized by varying the impact parameter at fixed energy. In the regime where momentum transfers reach the string scale, string effects appear subdominant to higher-loop gravitational processes, approximated via the eikonal. At smaller impact parameters, "diffractive" or "tidal" string excitation leads to processes dominated by highly excited strings. However, new evidence is presented that these excitation effects do not play a direct role in black hole formation, which corresponds to breakdown of gravitational perturbation theory and appears to dominate at sufficiently small impact parameters. The estimated amplitudes violate expected bounds on high-energy behavior for local theories.