Bonanno-Reuter regular black hole: quasi-resonances, grey-body factors and absorption cross-sections of a massive scalar field

Abstract: We study quasinormal modes of a massive scalar field in the background of the regular, quantum-corrected Bonanno-Reuter black hole, which arises from the renormalization group improvement of the Schwarzschild solution within the framework of asymptotically safe gravity. The analysis is performed in both the time and frequency domains. We find that increasing the mass of the field leads to a strong suppression of the damping rate, and extrapolation to larger masses indicates the emergence of arbitrarily long-lived oscillations, or quasi-resonances. In the time domain, the late-time decay follows an asymptotic behavior that differs from the power-law tails of the classical Schwarzschild case. Furthermore, we compute the grey-body factors and absorption cross-sections for the massive scalar field and show that the grey-body factors decrease as the field mass increases, effectively shifting the emitted radiation spectrum toward higher frequencies.