The Breakdown of String Perturbation Theory for Many External Particles

TL;DR

This paper investigates the limitations of string perturbation theory when applied to scattering amplitudes with many low-energy external particles, revealing a breakdown in this regime and discussing implications for the information paradox.

Contribution

It demonstrates that string perturbation theory fails in the large particle number limit using moduli space volume growth and numerical evidence, with implications for the information paradox.

Findings

String perturbation theory breaks down at large external particle numbers.

Growth of moduli space volume indicates perturbation theory failure.

Numerical evidence supports the theoretical argument.

Abstract

We consider massless string scattering amplitudes in a limit where the number of external particles becomes very large, while the energy of each particle remains small. Using the growth of the volume of the relevant moduli space, and by means of independent numerical evidence, we argue that string perturbation theory breaks down in this limit. We discuss some remarkable implications for the information paradox.