Scattering of massless scalar waves by Reissner-Nordstr\"om black holes

TL;DR

This paper investigates how charged black holes scatter massless scalar waves, revealing how increasing charge affects scattering patterns, absorption, and the glory phenomenon, with results validated against semi-classical geodesic approximations.

Contribution

It provides a detailed numerical analysis of scalar wave scattering by Reissner-Nordström black holes, highlighting the influence of charge on scattering and absorption characteristics, and compares results with semi-classical methods.

Findings

Absorption cross section decreases with increasing black hole charge.

Angular width of scattering fringes increases as charge increases.

The glory in the backward direction widens with higher charge.

Abstract

We present a study of scattering of massless planar scalar waves by a charged non-rotating black hole. Partial wave methods are applied to compute scattering and absorption cross sections, for a range of incident wavelengths. We compare our numerical results with semi-classical approximations from a geodesic analysis, and find excellent agreement. The glory in the backward direction is studied, and its properties are shown to be related to the properties of the photon orbit. The effects of black hole charge upon scattering and absorption are examined in detail. As the charge of the black hole is increased, we find that the absorption cross section decreases, and the angular width of the interference fringes of the scattering cross section at large angles increases. In particular, the glory spot in the backward direction becomes wider. We interpret these effects under the light of our geodesic analysis.