Scattering of a Long Cosmic String by a Rotating Black Hole

TL;DR

This paper investigates how an infinitely long cosmic string is scattered by a rotating black hole, revealing displacement effects, resulting kinks, and comparing numerical results with weak-field and non-rotating cases.

Contribution

It provides a detailed numerical analysis of cosmic string scattering by rotating black holes, including displacement and kink formation, extending previous non-rotating black hole studies.

Findings

String displacement depends on impact parameter and velocity.

Late-time solutions feature propagating kinks and anti-kinks.

Numerical results agree with weak-field approximation for large impact parameters.

Abstract

The scattering of a straight, infinitely long string by a rotating black hole is considered. We assume that a string is moving with velocity v and that initially the string is parallel to the axis of rotation of the black hole. We demonstrate that as a result of scattering, the string is displaced in the direction perpendicular to the velocity by an amount kappa(v,b), where b is the impact parameter. The late-time solution is represented by a kink and anti-kink, propagating in opposite directions at the speed of light, and leaving behind them the string in a new ``phase''. We present the results of the numerical study of the string scattering and their comparison with the weak-field approximation, valid where the impact parameter is large, b/M >> 1, and also with the scattering by a non-rotating black hole which was studied in earlier works.