Image of Quantum Improved Regular Kerr Black Hole and Parameter Constraints from EHT Observations

Abstract: Quantum Improved Regular Kerr (QIRK) black hole is a rotating regular black hole model constructed based on the asymptotic safety method. The model eliminates the ring singularity and prevents the formation of closed timelike curves, while retaining well-defined thermodynamic properties. Given these properties, probing the observable features of the QIRK black hole is important. In this work, we numerically determine the region of parameter space in which the QIRK spacetime remains regular, admits an event horizon, and is free of closed timelike curves. Subsequently, we simulate images of a QIRK black hole surrounded by a thin accretion disk. We find the primary effect of the quantum correction parameter, $\widetilde{\omega}$, is a systematic reduction in the overall observed intensity, with only subtle effects on the image geometry. Using observational data from the Event Horizon Telescope (EHT) for Sgr A* and M87*, we further constrain the parameters of the QIRK black hole. Moreover, since there exist QIRK parameters that are free of singularities and can admit closed timelike curves, we investigate the images of CTCs under these conditions. These results reveal the distinctive observational features of the QIRK spacetime and provide a quantitative basis for assessing its viability as an astrophysical candidate.