Radiative and Jet Signatures of Regular Black Holes in Quantum-Corrected Gravity

TL;DR

This work probes regular rotating black holes in asymptotically safe gravity (ASG) where a scale-dependent Newton constant, governed by the deformation parameter $\xi$, alters near-horizon geometry while preserving Kerr-like asymptotics. By deriving a Kerr-like metric with ASG corrections, the authors compute the thin-disk radiative efficiency $\eta_{NT}$ and the Blandford–Znajek jet power $P_{BZ}$ as functions of $(a,\xi)$, linking horizon-scale physics to observable high-energy phenomena. Joint constraints from six stellar-mass BHs show that several systems (e.g., A0620--00, GRO J1655--40, XTE J1550--564) admit consistent regions in $(a,\xi)$ with modest deformation, whereas high-spin systems like GRS 1915+105 exhibit tensions, indicating either tighter bounds on $\xi$ or missing physics. A methodological contribution presents a physically transparent procedure to obtain axisymmetric rotating spacetimes from static seeds via a modified Newman–Janis approach, yielding a Kerr-like rotating metric consistent with Einstein equations in an orthonormal frame. Overall, the results demonstrate that quantum corrections confined to the strong-field regime can leave detectable imprints on accretion and jet processes, making radiative efficiency and jet power valuable probes of horizon-scale quantum gravity.

Abstract

We investigate regular rotating black holes predicted by asymptotically safe gravity, where the Newton constant varies with energy scale and modifies the near horizon geometry. These solutions remain asymptotically flat and avoid central singularities while differing from the classical Kerr spacetime in the strong field region. We compute the radiative efficiency of thin accretion disks and the jet power from the Blandford Znajek mechanism, both of which depend on the deformation parameter of the model. The predictions are compared with observational estimates for six stellar mass black holes. For systems with low or moderate spin the model reproduces the data within reported uncertainties, while rapidly spinning sources such as GRS 1915 105 present tensions and point to a restricted deformation range or the need for additional physics. The results show that quantum corrections confined to the strong gravity regime can still leave detectable imprints on high energy astrophysical processes. Radiative and jet based diagnostics therefore provide a promising method to test the geometry near the horizon and to explore possible signatures of quantum gravity in observations.

Figures (11)

• Figure 1: Variation of the lapse function $F(r)$ with radial coordinate $r$ for various values of the quantum correction parameter $\xi$. For $\xi = 0$, the Schwarzschild solution is recovered. Two-horizon behavior emerges for $\xi \lesssim \xi_{\rm crit}$.
• Figure 2: Parameter boundaries for horizon formation in the $(a, \xi)$ parameter space.
• Figure 3: Variation of disk radiative efficiency $\eta$ with spin and ASG parameter $\xi$ for two representative cases.
• Figure 4: Variation of disk radiative efficiency $\eta$ with spin and ASG parameter $\xi$ for two representative cases.
• Figure 5: Variation of the disk radiative efficiency with the spin parameter $a$ for the same physical case. The upper panel shows the full parameter range, while the lower panel zooms into a shorter range for clarity.