https://doi.org/10.1140/epjc/s10052-015-3370-4
Regular Article - Theoretical Physics
Scalar clouds in charged stringy black hole-mirror system
Department of Physics, Henan Normal University, Xinxiang, 453007, China
* e-mail: 021149@htu.cn
Received:
30
January
2015
Accepted:
20
March
2015
Published online:
9
April
2015
It was reported that massive scalar fields can form bound states around Kerr black holes (Herdeiro and Radu, Phys. Rev. Lett. 112:221101, 2014). These bound states are called scalar clouds; they have a real frequency , where
is the azimuthal index and
is the horizon angular velocity of Kerr black hole. In this paper, we study scalar clouds in a spherically symmetric background, i.e. charged stringy black holes, with the mirror-like boundary condition. These bound states satisfy the superradiant critical frequency condition
for a charged scalar field, where
is the charge of the scalar field, and
is the horizon’s electrostatic potential. We show that, for the specific set of black hole and scalar field parameters, the clouds are only possible for specific mirror locations
. It is shown that analytical results of the mirror location
for the clouds perfectly coincide with numerical results in the
regime. We also show that the scalar clouds are also possible when the mirror locations are close to the horizon. Finally, we provide an analytical calculation of the specific mirror locations
for the scalar clouds in the
regime.
© SIF and Springer-Verlag Berlin Heidelberg, 2015