Narrow Results

The AdS moving mirror has a suite of interesting characteristics: (1) constant negative energy flux emission, (2) negative finite total energy emission, (3) Planck-distributed scalar particle production, and (4) asymptotic uniform acceleration. Here, we briefly explore the outstanding worldline, its connection to AdS space, the quantum radiation from the mirror, and the classical radiation from its moving point charge counterpart.

It is known that for self-gravitating radiation stars in anti-de Sitter (AdS) spacetime, there is a critical dimension, larger than it, the stars always maintain stability with any central energy density ${\rho }_c$; smaller than it, there is a maximal mass for the ${\rho }_c$ and when the ${\rho }_c$ continues to increase, the total mass of stars becomes a function of the ${\rho }_c$, and the function appears as an oscillation behavior and therefore the stars become unstable. In this paper we extend this study to the nonlinear case, in this case the equation of state is $P=a{\rho }^b$, in AdS spacetime, where a and b are two constant parameters. For the nonlinear case,the equations of gravitational field are more complicated, so the relation of total mass to the central energy density is numerically investigated. In particular, the effect of the two parameters a and b and the relation between spacetime dimension d, mass and ${\rho }_c$ are analyzed. We find that the critical dimension changes when the parameters a and b vary, namely the equation of state. In particular, the critical dimension decreases when b decreases.

In this paper, we present the static charged solutions of quartic quasi-topological gravity in the presence of a nonlinear electromagnetic field. Two branches of these solutions present black holes with one or two horizons or a naked singularity depending on the charge and mass of the black hole. The entropy of the charged black holes of fourth-order quasi-topological gravity through the use of Wald formula is computed and the mass, temperature and the charge of these black holes are found as well. We show that black holes with spherical, flat and hyperbolical horizon in quasi-topological gravity are stable for any allowed quasi-topological parameters. We also investigate the stability of nonlinear charged black holes.

The latest findings of static and spherically symmetric black hole solution give a potential platform to investigate the novel four-dimensional Einstein Gauss–Bonnet gravity. In order to obtain a rotating black hole solution, we first adopt the Newman Janis algorithm and study the structure of its horizons. To analyze the said black hole shadow, we move forward to compute expressions of the celestial coordinates using the geodesic equations. Furthermore, we provide a detailed analysis of the shadow size and its distortion parameter, adopting the Hioki and Maeda method, together with the applications of a supermassive black hole shadow in the center of nearby galaxy Messier 87 and obtained constraints on the relationships of spin and charge. From the obtained results, we demonstrate that both spin and coupling parameters of the black hole have a substantial influence on shadow structure. The increment in the values of these parameters diminishes the shadow radius. We also study the energy emission rate using the Hawking temperature. Furthermore, it is shown that whenever the collision of two electrically neutral test particles takes place in the vicinity of the black hole horizon, the Gauss–Bonnet black hole may serve as a particle accelerator with an infinitely large center of mass energy.