Scalar and Dirac quasinormal modes of scalar-tensor-Gauss-Bonnet black holes

This study explores the scalar and Dirac quasinormal modes pertaining to a class of black hole solutions in the scalar-tensor-Gauss-Bonnet theory. The black hole metrics in question are novel analytic solutions recently derived in the extended version of the theory, which effectively follows at the level of the action of string theory. Owing to the existence of a nonlinear electromagnetic field, the black hole solution possesses a nonvanishing magnetic charge. In particular, the metric is capable of describing black holes with distinct characteristics by assuming different values of the ADM mass and the magnetic charge. This study investigates the scalar and Dirac perturbations in these black hole spacetimes; in particular, we focus on two different types of solutions, based on distinct horizon structures. The properties of the complex frequencies of the obtained dissipative oscillations are investigated, and the stability of the metric is subsequently addressed. We also elaborate on the possible implications of this study.