Quasinormal modes of scalarized black holes in the Einstein-Maxwell-Scalar theory

We perform the stability analysis on scalarized charged black holes in the Einstein-Maxwell-Scalar (EMS) theory by computing quasinormal mode spectrum. It is noted that the appearance of these black holes with scalar hair is closely related to the instability of Reissner-Nordstrom black holes without scalar hair in the EMS theory. The scalarized charged black hole solutions are classified by the order number of n = 0,1,2, ... , where n = 0 is called the fundamental branch and n = 1, 2, ... denote the n excited branches. Here, we show that the n = 1, 2 excited black holes are unstable against the s(l = 0)-mode scalar perturbation, while the n = 0 black hole is stable against all scalar-vector-tensor perturbations. This is consistent with other scalarized black holes without charge found in the Einstein-Scalar-Gauss-Bonnet theory. (C) 2019 The Author(s). Published by Elsevier B.V.