Effects of the external magnetic field on the Lense–Thirring precession

In this paper, we study the effects of the external magnetic field on the Lense–Thirring (LT) precession of a test gyroscope attached to an observer in magnetized black hole spacetime. For this, we consider a Kerr–Newman black hole embedded in the external magnetic field. The LT precession of a test gyroscope diverges near the ergosurface and remains finite everywhere outside the ergosurface. It is seen that by increasing the external magnetic field, the LT precession frequency in the region of large [Formula: see text] decreases as [Formula: see text] increases, while the precession frequency in the region of small [Formula: see text] increases as [Formula: see text] increases, whereas it increases with increasing the charge of the black hole. The LT precession of a test gyroscope attached to observers moving along the directions close to the polar axis is greater than that of the observer moving in the equatorial plane.

Absorption by stringy black holes

We investigate the absorption of planar massless scalar waves by a charged rotating stringy black hole, namely a Kerr–Sen black hole. We compute numerically the absorption cross section and compare our results with those of the Kerr–Newman black hole, a classical general relativity solution. In order to better compare both charged black holes, we define the ratio of the black hole charge to the extreme charge as Q. We conclude that Kerr–Sen and Kerr–Newman black holes have a similar absorption cross section, with the difference increasing for higher values of Q.

Analysis and research on superradiant stability of Kerr-sen Black Hole

Kerr-Sen black holes have stretchon parameters and hidden conformal symmetries. The superradiation stability and steady-state resonance are worth further study. This is the research motivation of this paper.In that article, a new variable y is added here to expand the results of the above article. When$\sqrt{2a^2}/{r^2_+}< \omega< m\varOmega_H+q\varPhi_H$,so the Kerr-sen black hole is superradiantly stable at that time,similar to the superradiation result of the Kerr-Newman black hole.

Analysis of Superradiation Stability of Kerr-Newman Black Hole Using Curve integral

In this article, a new variable y is added here to expand the results of the above article.We use the properties of the Laurent series and the Cauchy integral. When y is greater than a certain limit, the effective potential of the equation does not have a pole, then there is no potential well outside the event horizon, when p 2(a 2 + Q2)/r2 + < ω < mΩH + qΦH,so the Kerr-Newman black hole is superradiantly stable at that time.

Quantum gravity effects on spectroscopy of Kerr-Newman black hole in gravity’s rainbow

Quantum gravity effects on spectroscopy for the charged rotating gravity’s rainbow are investigated. By utilizing an action invariant obtained from particles tunneling through the event horizon, the entropy and area spectrum for the modified Kerr-Newman black hole are derived. The equally spaced entropy spectrum characteristic of Bekenstein’s original derivation is recovered. And, the entropy spectrum is independent of the energy of the test particles, although the gravity’s rainbow itself is the energy dependent. Such, the quantum gravity effects of gravity’s rainbow has no influence on the entropy spectrum. On the other hand, due to the spacetime quantum effects, the obtained area spectrum is different from the original Bekenstein spectrum. It is not equidistant and has the dependence on the horizon area. And that, by analyzing the area spectrum from a specific rainbow functions, a minimum area with Planck scale is derived for the event horizon. At this, the area quantum is zero and the black hole radiation stops. Thus, the black hole remnant for the gravity’s rainbow is obtained from the area quantization. In addition, the entropy for the modified Kerr-Newman black hole is calculated and the quantum correction to the area law is obtained and discussed.

Analysis of Superradiation Stability of Kerr-Newman Black Hole Using Curve integral

In this article, a new variable y is added here to expand the results of the above article.We use the properties of the Laurent series and the Cauchy integral. When y is greater than a certain limit, the effective potential of the equation does not have a pole, then there is no potential well outside the event horizon, when p 2(a 2 + Q2)/r2 + < ω < mΩH + qΦH,so the Kerr-Newman black hole is superradiantly stable at that time.

Analysis of Superradiation Stability of Kerr-Newman Black Hole Using Curve integral

In this article, a new variable y is added here to expand the results of the above article.We use the properties of the Laurent series and the Cauchy integral. When y is greater than a certain limit, the effective potential of the equation does not have a pole, then there is no potential well outside the event horizon, when $\sqrt{2(a^2+Q^2)}/{r^2_+}&lt; \omega&lt; m\varOmega_H+q\varPhi_H$,so\ the Kerr-Newman black hole is superradiantly stable at that time.

Quantum gravity corrections to tunneling of spin-1/2 fermions from Kerr–Newman Black Hole

In this paper, we solve the Dirac Equation in curved space–time, modified by the generalized uncertainty principle, in the presence of an electromagnetic field. Using this, we study the tunneling of [Formula: see text]-spin fermions from Kerr–Newman black hole. Corrections to the Hawking temperature and entropy of the black hole due to quantum gravity effects are also discussed.

Analytic study of superradiant stability of Kerr–Newman black holes under charged massive scalar perturbation

The superradiant stability of a Kerr–Newman black hole and charged massive scalar perturbation is investigated. We treat the black hole as a background geometry and study the equation of motion of the scalar perturbation. From the radial equation of motion, we derive the effective potential experienced by the scalar perturbation. By a careful analysis of this effective potential, it is found that when the inner and outer horizons of Kerr–Newman black hole satisfy $$\frac{r_-}{r_+}\leqslant \frac{1}{3}$$ r - r + ⩽ 1 3 and the charge-to-mass ratios of scalar perturbation and black hole satisfy $$ \frac{q}{\mu }\frac{Q}{ M}>1 $$ q μ Q M > 1 , the Kerr–Newman black hole and scalar perturbation system is superradiantly stable.