Scattering of charged massive scalar waves by Kerr-Newman black holes

TL;DR

This paper analyzes how charged massive scalar waves scatter off Kerr-Newman black holes, revealing effects of charge, rotation, and superradiance on scattering patterns and flux enhancements.

Contribution

It systematically examines the influence of black hole charge, electromagnetic interactions, and field mass on equatorial scattering, providing new insights into charged black hole wave interactions.

Findings

Frame-dragging shifts glory away from backward direction.

Flux intensity increases with field mass and Lorentz attraction.

Superradiance enhances scattering cross sections at specific angles.

Abstract

The scattering of charged massive scalar waves by Kerr-Newman black holes, with incidence along the equatorial plane, is investigated in this work. The differential scattering cross section is computed using the partial wave method, with the forward divergence handled via the series reduction technique. For the first time, we systematically examine the influence of the black hole charge, electromagnetic interactions, and field mass on the equatorial cross section. Our results reveal that regardless of whether the electromagnetic interaction is present or not, the frame-dragging effect shifts the glory away from the exact backward direction and can place interference minima there, contrasting with the on-axis scattering case. The average scattered flux intensity at the medium to large scattering angles exhibits a large enhancement as the Lorentz attraction or field mass increases, particularly in the slowly rotating regime, with the enhancement being frequency-dependent. When superradiance occurs, we observe that the cross section in the prograde scattering angles ($\sim 135^{\circ} < \phi < 270^{\circ}$) increases as the black hole spin increases, due to enhanced prograde partial wave contributions. Meanwhile, the superradiant scattering cross section increases in all (except the forward) directions when the Lorentz force becomes more repulsive. These findings highlight unique equatorial-plane signatures of charged, rotating spacetimes, distinguishing them from prior on-axis analyses.