Quasinormal modes and absorption of a massless scalar field for the magnetic Gauss-Bonnet black hole

We study the massless scalar quasinormal frequencies of an asymptotically flat static and spherically symmetric black hole with a nonzero magnetic charge in four-dimensional extended scalar-tensor-Gauss-Bonnet theory. The results show that the real part of the quasinormal frequency becomes larger and the imaginary part becomes smaller with increasing the magnetic charge or the angular harmonic index. The existence of magnetic charges will reduce the damping of scalar perturbation, but increase the frequency. We also study the absorption cross-section of the scalar field in this black hole. We find that its curve will become lower as the magnetic charge increases, i.e. the magnetic charge will weaken the absorption capacity of the black hole. Meanwhile, the high-frequency limit of the total absorption cross-section is just the area of black hole shadow.

Automated summary

The study shows that the real part of quasinormal frequency increases and the imaginary part decreases with an increase in magnetic charge or angular harmonic index. Magnetic charges reduce the damping of scalar perturbation but increase the frequency. The absorption cross-section of the scalar field in a black hole decreases as the magnetic charge increases, weakening the black hole's absorption capacity. The total absorption cross-section's high-frequency limit is the area of the black hole shadow.