The asymptotically safe gravity is based on the idea that the main
contribution to the Schwarzschild-like black hole spacetime is due to the value
of the gravitational coupling which depends on the distance from the origin and
approaches its classical value in the far zone. However, at some stage this
approach has an arbitrariness of choice of some identification parameter. The
two cases of identification are considered here: first, by the modified proper
length (the Bonanno-Reuter metric), and second, by the Kretschmann scalar (the
Held-Gold-Eichhorn metric, which coincides, up to the redefinition of
constants, with the Hayward metric). Even though the quasinormal modes of these
metrics have been extensively studied, a number of interesting points were
missed. We have found that quasinormal modes are qualitatively similar for both
types of identification. The deviation of the fundamental mode from its
Schwarzschild limit may be a few times larger than it was claimed in the
previous studies. The striking deviation from the Schwarzschild limit occurs
for overtones, being as large as hundreds of percent even when the fundamental
mode is almost coinciding with the Schwarzschild one. This happens because the
above metrics are very close to the Schwarzschild one everywhere, except a
small region near the event horizon, which is crucial for overtones. The
spectrum of both metrics contains purely imaginary (non-oscillatory) modes,
which, for some values of parameters, can appear already at the second
overtone.
Preprint
Comment: 12 pages, 7 figures
Subjects: General Relativity and Quantum Cosmology; Astrophysics - High Energy Astrophysical Phenomena; High Energy Physics - Theory