Portrait of the String as a Random Walk

TL;DR

This paper models highly excited closed strings as a convolution of Brownian motions, revealing their space-time evolution and the emergence of singular classical backgrounds due to decoherence effects.

Contribution

It introduces a novel approach to describe string dynamics through Brownian motion and links decoherence to classical singularities in string scattering.

Findings

String evolution resembles a convolution of Brownian motions

Classical backgrounds reproducing scattering are time-dependent and singular

Decoherence leads to classical singularities without strong gravity effects

Abstract

In this paper we analyze a Rutherford type experiment where light probes are inelastically scattered by an ensemble of excited closed strings, and use the corresponding cross section to extract density-density correlators between different pieces of the target string. We find a wide dynamical range where the space-time evolution of typical highly excited closed strings is accurately described as a convolution of brownian motions. Moreover, we show that if we want to obtain the same cross section by coherently scattering probes off a classical background, then this background has to be time-dependent and singular. This provides an example where singularities arise, not as a result of strong gravitational self-interactions, but as a byproduct of the decoherence implicit in effectively describing the string degrees of freedom as a classical background.