Scattering of scalar waves by rotating black holes

Citation
K. Glampedakis et N. Andersson, Scattering of scalar waves by rotating black holes, CLASS QUANT, 18(10), 2001, pp. 1939-1966
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
CLASSICAL AND QUANTUM GRAVITY
ISSN journal
0264-9381 → ACNP
Volume
18
Issue
10
Year of publication
2001
Pages
1939 - 1966
Database
ISI
SICI code
0264-9381(20010521)18:10<1939:SOSWBR>2.0.ZU;2-8
Abstract
We study the scattering of massless scalar waves by a Kerr black hole by le tting plane monochromatic waves impinge on the black hole. We calculate the relevant scattering phase-shifts using the Prufer phase-function method, w hich is computationally efficient and also reliable for high frequencies an d/or large values of the angular multipole indices (l, m), We use the obtai ned phase-shifts and the partial-wave approach to determine differential cr oss sections and deflection functions. Results for off-axis scattering (wav es incident along directions misaligned with the black hole's rotation axis ) are obtained for the first time. Inspection of the off-axis deflection fu nctions reveals the same scattering phenomena as in Schwarzschild scatterin g. In particular, the cross sections are dominated by the glory effect and the forward (Coulomb) divergence due to the long-range nature of the gravit ational field. In the rotating case the overall diffraction pattern is 'fra me-dragged' and as a result the glory maximum is not observed in the exact backward direction. We discuss the physical reason for this behaviour, and explain it in terms of the distinction between prograde and retrograde moti on in the Kerr gravitational field. Finally, we also discuss the possible i nfluence of the so-called superradiance effect on the scattered waves.