Gravito-electromagnetic perturbations and QNMs of regular black holes

In the framework of Einstein's gravity coupled to nonlinear electromagnetic fields, we study gravito-electromagnetic perturbations of magnetic regular black holes (BHs). The master equations of perturbations are obtained through Chandrasekhar's formulation, from which it can be seen, different from the electric counterparts, for magnetic BHs gravitational perturbations with odd-parity coupled only to the electromagnetic perturbations with even-parity. We solve the master equations numerically and obtain quasinormal modes (QNMs) for three typical regular BHs. Results show that QNMs of distinct regular BHs differ significantly, and they differ from that of the Reissner-Nordstrom BH as well. Indications of these results on the stability of these regular BHs are discussed in detail.