Gravitational Scattering of Cosmic Strings by Non-Rotating Black Holes

TL;DR

This study investigates how cosmic strings interact gravitationally with non-rotating black holes, providing numerical and analytical insights into scattering, loop formation, and capture phenomena across various impact parameters and velocities.

Contribution

It offers new numerical results and analysis on cosmic string scattering by black holes, including near-critical impact parameters and the role of string tension, extending previous analytical work.

Findings

String scattering is highly sensitive near critical impact parameters.

Ultra-relativistic regimes show loop formation and shock wave scattering.

A comprehensive capture curve for all velocities is provided.

Abstract

This paper discusses the gravitational scattering of a straight, infinitely long test cosmic string by a black hole. We present numerical results that probe the two-dimensional parameter space of impact parameter and initial velocity and compare them to approximate perturbative solutions derived previously. We analyze string scattering and loop formation in the ultra-relativistic regime and compare these results with analytical results for string scattering by a gravitational shock wave. Special attention is paid to regimes where the string approaches the black hole at near-critical impact parameters. The dynamics of string scattering in this case are highly sensitive to initial data and transient phenomena arise while portions of the string dwell in the strong gravitational field near the event horizon of the black hole. The role of string tension is also investigated by comparing the scattering of a cosmic string to the scattering of a tensionless "dust" string. Finally, the problem of string capture is revisited in light of these new results, and a capture curve covering the entire velocity range ($0 < v \le c$) is given.