Folded Strings Falling into a Black Hole

TL;DR

This paper derives all classical string solutions in two-dimensional curved spacetimes, including black holes, revealing new phenomena such as string tunneling into singularities beyond classical particle behavior.

Contribution

It provides a comprehensive classification of classical string solutions in curved backgrounds and uncovers novel effects like string tunneling into black hole singularities.

Findings

Classical solutions include oscillating folded strings in black hole spacetimes.

Strings can tunnel into regions beyond the classical singularity, unlike particles.

The solutions are constructed using lattice-like patches and transfer matrices.

Abstract

We find all the classical solutions (minimal surfaces) of open or closed strings in {\it any} two dimensional curved spacetime. As examples we consider the SL(2,R)/R two dimensional black hole, and any 4D black hole in the Schwarzschild family, provided the motion is restricted to the time-radial components. The solutions, which describe longitudinaly oscillating folded strings (radial oscillations in 4D), must be given in lattice-like patches of the worldsheet, and a transfer operation analogous to a transfer matrix determines the future evolution. Then the swallowing of a string by a black hole is analyzed. We find several new features that are not shared by particle motions. The most surprizing effect is the tunneling of the string into the bare singularity region that lies beyond the black hole that is classically forbidden to particles.