Behaviour of Singularities of the Kerr-Newman and the Kerr-Sen Solutions by Arbitrary Boost

TL;DR

This paper investigates how singularities of rotating black holes, including Kerr-Newman and Kerr-Sen solutions, behave under arbitrary boosts, providing explicit formulas and discussing ultrarelativistic limits.

Contribution

It introduces a simple algorithm to derive explicit metrics and singularity positions for boosted rotating black holes in various directions and speeds.

Findings

Explicit expressions for metrics and singularities under boosts.

Analysis of ultrarelativistic limit non-smoothness.

Extension to Kerr-Sen black hole solutions in string theory.

Abstract

Behaviour of singularities of the rotating black holes under an arbitrary boost is considered on the basis of a complex representation of the Kerr theorem. We give a simple algorithm allowing to get explicit expressions for the metric and the position of the singularities for arbitrary direction and magnitude of the boost, including the ultrarelativistic case. The non-smoothness of the ultrarelativistic limit is discussed. The Kerr-Sen BH-solution to low energy string theory is also analyzed.