Stationary scalar clouds around a rotating BTZ-like black hole in the Einstein-bumblebee gravity

Abstract

We have studied stationary clouds of massive scalar fields around a rotating BTZ-like black hole in the Einstein-bumblebee gravity, by imposing the Robin type boundary conditions at the AdS boundary. We establish, by scanning the parameter space, the existence of \textit{fundamental} stationary scalar clouds ($i.e.$, the overtone number $n=0$). In particular, we observe that the Lorentz symmetry breaking parameter $s$ and the quantum number $k$ play an opposite role in determining scalar clouds, which indicates the existence of \textit{degenerate} scalar clouds. To illustrate the fact that scalar clouds may only be supported for the $n=0$ case, we have analyzed the impact of various parameters on scalar quasinormal modes. It is shown that the Lorentz symmetry breaking parameter $s$ does not change the superradiance condition, and superradiant instabilities only appear for the fundamental modes. Our work shows that the Lorentz symmetry breaking provides richer physics in stationary scalar clouds around black holes.