Superradiance or total reflection?

TL;DR

This study numerically investigates massless scalar fields on Kerr black holes, revealing that incident waves are almost perfectly reflected rather than extracting energy via superradiance, challenging previous expectations.

Contribution

The paper demonstrates through numerical simulations that incident scalar waves are reflected rather than superradiantly amplified, providing new insights into wave behavior around Kerr black holes.

Findings

Incident waves are nearly perfectly reflected.

Superradiance does not occur under the studied conditions.

Energy extraction via superradiance is not observed.

Abstract

Numerical evolution of massless scalar fields on Kerr background is studied. The initial data specifications are chosen to have compact support separated from the ergoregion and to yield nearly monochromatic incident wave packets. The initial data is also tuned to maximize the effect of superradiance. Evidences are shown indicating that instead of the anticipated energy extraction from black hole the incident radiation fail to reach the ergoregion rather it suffers a nearly perfect reflection.