Numerical study of superradiant instability for charged stringy black hole–mirror system

We numerically study the superradiant instability of charged massless scalar field in the background of charged stringy black hole with mirror-like boundary condition. We compare the numerical result with the previous analytical result and show the dependencies of this instability upon various values of black hole charge Q, scalar field charge q  , and mirror radius rmrm. Especially, we have observed that imaginary part of BQN frequencies grows with the scalar field charge q rapidly.