Conditions for superradiant instability of the Kerr-Newman black holes

We find two conditions for superradiant instability of Kerr-Newman black holes under a charged massive scalar perturbation by analyzing the asymptotic scalar potential and far-region wave function. Actually, they correspond to the condition for getting a trapping well. Also, we obtain the conditions for superradiant stability of Kerr-Newman black holes which states that there is no trapping well. The analysis is applied to Kerr black holes to find a condition for superradiant instability.

Automated summary

The conditions for superradiant instability of Kerr-Newman black holes under a charged massive scalar perturbation are found by analyzing the asymptotic scalar potential and far-region wave function. It is also discovered that the conditions for superradiant stability of Kerr-Newman black holes correspond to the absence of a trapping well. The analysis is applied to Kerr black holes to find a condition for superradiant instability.