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Quantum Improved Regular Kerr (QIRK) Black Hole is a rotating regular black hole based on the asymptotic safety method. This black hole not only resolves ring singularity and avoids closed timelike curves, but also has well defined thermodynamics. Therefore, it is crucial to find some observable features of this rotating black hole. In this article, we numerically determine the specific parameter range of the QIRK black hole after ensuring the three key properties mentioned above, while investigating its black hole shadow, we find that the extremal QIRK black hole, under a critical angular momentum $a_{\mathrm{cri}}$, can have a similar shadow to the non extremal Kerr black hole. Furthermore, with recent observations from the Event Horizon Telescope (EHT) of Sgr A* and earlier observations of the supermassive black hole M87*, we constrain the QIRK black hole using observational data and explore its potential as an astronomical object., Comment: 23 pages,14 figures

We study the optical appearance of Schwarzschild-de Sitter and Reissner-Nordstr\"{o}m-de Sitter black holes viewed by distant observers inside cosmological horizons. Unlike their asymptotically flat counterparts, due to the positive cosmological constant, there are outermost stable circular orbits in the spacetimes, resulting in significant outer edges in the images. Besides, when the Reissner-Nordstr\"{o}m-de Sitter black hole has a stable Cauchy horizon, the photons from the preceding companion universe can be received by the observer in our universe. These rays create a multi-ring structure in the image. Since the stable Cauchy horizon violates the strong cosmic censorship conjecture, this novel image shed some light on the test of the conjecture by astronomical observations., Comment: 15 pages, 15 figures, references and figures are updated, accepted by Phys. Rev. D

The strong cosmic censorship conjecture, which states that the evolution of generic initial data will always produce a globally hyperbolic spacetime, is hard to be tested by astronomical observations. In this paper, we study the appearance of the regular black hole without mass inflation, which violates the strong cosmic censorship conjecture. Since the inner horizon is stable, the photons entering the two horizons of the regular black hole in the preceding companion universe can come out from the white hole in our universe. These rays create a novel multi-ring structure, which is significantly different from the image of the Schwarzschild black hole. This serves a potential method to test the strong cosmic censorship conjecture., Comment: 12 pages, 15 figures, tiltle is changed, references and discussion are added, accepted by Phys. Rev. D

We analyse the stability of the inner horizon of the quantum-corrected black hole which is proposed in loop quantum gravity as the exterior of the quantum Oppenheimer-Snyder and Swiss Cheese models. It is shown that the flux and energy density of a test scalar field measured by free-falling observers are both divergent near the Cauchy horizon. By considering the generalized Dray-'t Hooft-Redmond relation which is independent of the field equation, we find that the mass inflation always happens and the scalar curvature and Kretschmann scalar are also divergent on the inner horizon. These suggest that the inner horizon is unstable and will probably turn into a null singularity. The results support the strong cosmic censorship hypothesis. However, this also implies that the quantum corrected model may not be the definitive endpoint as a regular black hole. Besides, it further proposes that it may be challenging to observe the astronomical phenomenon which depends on the existence of the inner horizon of the black hole., Comment: 13 pages, 1 figure

To ensure the light (emitted far away from the source of gravity) can arrive at the null infinity of an asymptotically flat spacetime, it is shown that the rate of Bondi mass aspect has to satisfy some conditions. In Einstein gravity theory, we find the sufficient condition implies a bound on the Bondi mass $m$, i.e., $|\dot{m}|\leqslant 0.3820~c^3/G$. This provides a new perspective on Dyson's maximum luminosity. However, in Brans-Dicke theory, the sufficient condition depends on the behavior of the radiation field of the scalar. Specifically, the photons can escape to the null infinity when the scalar gravitational radiation is not too large and the mass loss is not too fast., Comment: revtex, 12pages, 2 figures, typos are corrected, discussion is improved