2023-0207

• [2302.02133] Nonsingular black hole chemistry in 4D Einstein-Gauss-Bonnet gravity
Abstract: The EGB is an outcome of quadratic curvature corrections to the Einstein-Hilbert gravity action in the form of a Gauss-Bonnet (GB) term in  dimensions, and EGB gravity is topologically invariant in . Several ways have been proposed for regularizing the limit of EGB for non-trivial gravitational dynamics in . Motivated by the importance of AdS/CFT, we obtain an exact static spherically symmetric nonsingular black hole in  EGB gravity coupled to the nonlinear electrodynamics (NED) in an AdS spacetime. We interpret the negative cosmological constant  as the positive pressure, via , of the system's thermodynamic properties of the nonsingular black hole with an AdS background. We find that for , the black holes with are stable to thermal fluctuations and unstable otherwise. We also analyzed the Gibbs free energy to find that the small globally unstable black holes undergo a phase transition to the large globally stable black holes. Further, we study the  criticality of the system and then calculate the critical exponents to find that our system behaves like Van der Walls fluid.

Keywords: thermodynamics; regular black hole;

• [2302.02784] Accretion disk around regular black holes
Abstract: Regular black holes are crucially important as approaches to solving the singularity problem, and in this paper, the accretion disk of Bardeen and Hayward models have been studied. For this purpose, we calculated the physical properties of black holes, including radiant energy, luminosity derivative, temperature, and conversion efficiency of accretion mass into radiation. The obtained results show that the non-zero-free parameters of regular black holes cause the radius of the innermost stable circular orbit of the disk to shift to smaller values. As a result of this displacement, we saw an increase in the profiles of radiant energy, luminosity derivative, and temperature. We also find that Bardeen and Hayward's black holes are more efficient in converting mass to radiation than Schwarzschild. Finally, we compared the free parameter of these two black holes with the spin of the rotating black hole and found that the Bardeen and Hayward black holes can mimic the slowly rotating Kerr black hole.

Keywords: regular black hole; Accretion disk;