Dirac equation of spin particles and tunneling radiation from a Kinnersly black hole

In curved space-time, the Hamilton–Jacobi equation is a semi-classical particle equation of motion, which plays an important role in the research of black hole physics. In this paper, starting from the Dirac equation of spin 1/2 fermions and the Rarita–Schwinger equation of spin 3/2 fermions, respectively, we derive a Hamilton–Jacobi equation for the non-stationary spherically symmetric gravitational field background. Furthermore, the quantum tunneling of a charged spherically symmetric Kinnersly black hole is investigated by using the Hamilton–Jacobi equation. The result shows that the Hamilton–Jacobi equation is helpful to understand the thermodynamic properties and the radiation characteristics of a black hole.     

Particle dynamics around a dyonic charged black hole

In this article, we study the circular motion of particles and the well-known Penrose mechanism around a Kerr-Newman-Kasuya black hole spacetime. The inner and outer horizons, as well as ergosurfaces of the said black hole, are briefly examined under the effect of spin and dyonic charge. Moreover, by limiting our exploration to the equatorial plane, we discuss the characteristics of circular geodesics and investigate both photons, as well as marginally stable circular orbits. It is noted that black hole charge diminishing the radii of photon and marginally stable circular orbits. To investigate the nature of particle dynamics, we studied the effective potential and Lyapunov exponent. While inspecting the process of energy extraction, we derived the Wald inequality, which can help us to locate the energy limits of the Penrose process. Furthermore, we have found expressions for the negative energy states and the efficiency of energy extraction. The obtained result illustrates that both black hole rotation and dyonic charge contributes to the efficiency of energy extraction.     

Particles and Scalar Waves in Noncommutative Charged Black Hole Spacetime

In this paper we have discussed geodesics and the motion of test particle in the gravitational field of noncommutative charged black hole spacetime. The motion of massive and massless particle have been discussed seperately. A comparative study of noncommutative charged black hole and usual Reissner—Nordström black hole has been done. The study of effective potential has also been included. Finally, we have examined the scattering of scalar waves in noncommutative charged black hole spacetime.     

Observers in Kerr spacetimes: the ergoregion on the equatorial plane

We perform a detailed analysis of the properties of stationary observers located on the equatorial plane of the ergosphere in a Kerr spacetime, including light-surfaces. This study highlights crucial differences between black hole and the super-spinner sources. In the case of Kerr naked singularities, the results allow us to distinguish between “weak” and “strong ” singularities, corresponding to spin values close to or distant from the limiting case of extreme black holes, respectively. We derive important limiting angular frequencies for naked singularities. We especially study very weak singularities as resulting from the spin variation of black holes. We also explore the main properties of zero angular momentum observers for different classes of black hole and naked singularity spacetimes.     

Excitons and multi-exciton complexes bound to a two-dimensional hole layer at a silicon surface: the Kondo effect,the Coulomb blockade and a negative photoconductivity

The recombination radiation line of surface excitons and the recombination radiation line of multi-exciton complexes bound to a two-dimensional hole layer are observed in luminescence spectra of [100] silicon metal–oxide–semiconductor structures at low two-dimensional hole density. The circular polarization of these two lines in a transverse magnetic field is defined by the average electron spin. The hole spin contribution to the circular polarization is very small due to Kondo spin correlations of holes in the excitons and complexes and holes in the two-dimensional hole layer. The Coulomb blockade excludes a direct contribution of the complexes to a surface photoconductivity. Moreover, a significant negative photoconductivity of the two-dimensional holes is observed at high excitation levels, presumably as a result of the quantum scattering of the two-dimensional holes by the complexes. A shell model of surface multi-exciton complexes is introduced.     

Spin of the M87 Black Hole

Spin measurement of the 6.5 billion solar mass black hole in M87 from the Event Horizon Telescope image is the latest in a series that span a wide range in values, but that tend to share the feature of corotation between the accretion flow and black hole. The spin paradigm for black holes predicts very high black hole spin which in that framework is produced in its last significant merger. High black hole spin appears to be ruled out in the gap paradigm, however, which predicts early formation with a mass already in excess of 4 billion solar masses. In this picture, the black hole experiences slow evolution as it departs from its original radio quasar phase and over billions of years not only fails to double its mass but also falls short of regaining its original high spin, such that it is now compatible with a corotating accreting black hole whose dimensionless spin fits best in the range 0.2 < a < 0.5.     

Quantum electron levels in the field of a charged black hole

Stationary solutions of the Dirac equation in the metric of the charged Reissner–Nordstrom black hole are found. In the case of an extremal black hole, the normalization integral of the wave functions is finite, and the regular stationary solution is physically self-consistent. The presence of quantum electron levels under the Cauchy horizon can have an impact on the final stage of the Hawking evaporation of the black hole, as well as on the particle scattering in the field of the black hole.     

Equations of motion of a spinning relativistic particle in external fields

We consider the motion of a spinning relativistic particle in external electromagnetic and gravitational fields to first order in the external field but to arbitrary order in the spin. The influence of the spin on the particle trajectory is properly accounted for by describing the spin noncovariantly. Specific calculations are performed through second order in the spin. A simple derivation is presented for the gravitational spin-orbit and spin-spin interactions of a relativistic particle. We discuss the gravimagnetic moment (GM), a particular spin effect in general relativity. We show that for a Kerr black hole the gravimagnetic ratio, i.e., the coefficient of the GM, equals unity (just as the gyromagnetic ratio equals 2 for a charged Kerr hole). The equations of motion obtained for a spinning relativistic particle in an external gravitational field differ substantially from the Papapetrou equations. Zh. éksp. Teor. Fiz. 113, 1537–1557 (May 1998)     

Analysis of Absorbing Periodic Structures Formed by Cylindrical Electromagnetic Black Holes

Technical Physics - A 2D problem of electromagnetic plane wave scattering by 1D-periodic structures with cylindrical elements of electromagnetic black hole type arranged on a semi-infinite...     

Intrinsic electron spin relaxation due to the D'yakonov–Perel' mechanism in monolayer MoS2

Intrinsic electron spin relaxation due to the D'yakonov–Perel' mechanism is studied in monolayer Molybdenum Disulphide. An intervalley in-plane spin relaxation channel is revealed due to the opposite effective magnetic fields perpendicular to the monolayer Molybdenum Disulphide plane in the two valleys together with the intervalley electron–phonon scattering. The intervalley electron–phonon scattering is always in the weak scattering limit, which leads to a rapid decrease of the in-plane spin relaxation time with increasing temperature. A decrease of the in-plane spin relaxation time with the increase of the electron density is also shown.     

Collision of two rotating Hayward black holes

We investigate the spin interaction and the gravitational radiation thermally allowed in a head-on collision of two rotating Hayward black holes. The Hayward black hole is a regular black hole in a modified Einstein equation, and hence it can be an appropriate model to describe the extent to which the regularity effect in the near-horizon region affects the interaction and the radiation. If one black hole is assumed to be considerably smaller than the other, the potential of the spin interaction can be analytically obtained and is dependent on the alignment of angular momenta of the black holes. For the collision of massive black holes, the gravitational radiation is numerically obtained as the upper bound by using the laws of thermodynamics. The effect of the Hayward black hole tends to increase the radiation energy, but we can limit the effect by comparing the radiation energy with the gravitational waves GW150914 and GW151226.     

The effects of running gravitational coupling on rotating black holes

In this work we investigate the consequences of running gravitational coupling on the properties of rotating black holes. Apart from the changes induced in the space-time structure of such black holes, we also study the implications to Penrose process and geodetic precession. We are motivated by the functional form of gravitational coupling previously investigated in the context of infra-red limit of asymptotic safe gravity theory. In this approach, the involvement of a new parameter \({\tilde{\xi }}\) in this solution makes it different from Schwarzschild black hole. The Killing horizon, event horizon and singularity of the computed metric is then discussed. It is noticed that the ergosphere is increased as \({\tilde{\xi }}\) increases. Considering the black hole solution in equatorial plane, the geodesics of particles, both null and time like cases, are explored. The effective potential is computed and graphically analyzed for different values of parameter \({\tilde{\xi }}\). The energy extraction from black hole is investigated via Penrose process. For the same values of spin parameter, the numerical results suggest that the efficiency of Penrose process is greater in quantum corrected gravity than in Kerr Black Hole. At the end, a brief discussion on Lense–Thirring frequency is also done.     

Cooper instability of nonlocal spin polarons in the CuO<Subscript>2</Subscript> plane of high-temperature superconductors

The energy structure of nonlocal spin polarons has been obtained for the real structure of the CuO₂ plane of cuprate superconductors in the ensemble of such Fermi quasiparticles. A nonlocal spin polaron is formed due to the exchange interaction of the spin of an oxygen hole with the spins of the two nearest copper ions. The scattering amplitude of nonlocal spin polarons in the cooper channel calculated using the diagrammatic technique indicates that the spin and charge degrees of freedom are strongly correlated.     

Orbital and epicyclic motion of charged test particles around non-rotating Einstein-Æther black holes

The study of charged test particle dynamics in the combined black hole gravitational field and magnetic field around it could provide important theoretical insight into astrophysical processes around such compact object. We have explored the orbital and epicyclic motion of charged test particles in the background of non-rotating Einstein-Æther black holes in the presence of external uniform magnetic field. We numerically integrate the equations of motion and analyze the trajectories of the charged test particles. We examined the stability of circular orbits using effective potential technique and study the characteristics of innermost stable circular orbits. We analyze the key features of quasi-harmonic oscillations of charged test particles nearby the stable circular orbits in an equatorial plane of the black hole, and investigate the radial profiles of the frequencies of latitudinal as well as radial harmonic oscillations in dependence on the strength of magnetic field, mass of the black hole and dimensionless coupling constants of the theory. We demonstrate that the magnetic field and dimensionless parameters of the theory have strong influence on charged particle motion around Einstein-Æther black holes.     

Integrability of spinning particle motion in higher-dimensional rotating black hole spacetimes

We study the motion of a classical spinning particle (with spin degrees of freedom described by a vector of Grassmann variables) in higher-dimensional general rotating black hole spacetimes with a cosmological constant. In all dimensions n we exhibit n bosonic functionally independent integrals of spinning particle motion, corresponding to explicit and hidden symmetries generated from the principal conformal Killing-Yano tensor. Moreover, we demonstrate that in 4-, 5-, 6-, and 7-dimensional black hole spacetimes such integrals are in involution, proving the bosonic part of the motion integrable. We conjecture that the same conclusion remains valid in all higher dimensions. Our result generalizes the result of Page et?al. [Phys. Rev. Lett. 98, 061102 (2007)] on complete integrability of geodesic motion in these spacetimes.     

黑洞阴影在SSD中的位置和形状

假设旋转的黑洞在标准吸积盘内,在吸积盘的内边界等于最后稳定轨道的情况下,画出黑洞阴影在吸积盘的图像.通过定性和定量分析黑洞的形状和位置,发现对于相同质量的黑洞,黑洞阴影的大小及形状与黑洞的自旋参量有关.旋转黑洞阴影的形状和位置与它的旋转轴是不对称的,通过研究旋转轴与黑洞阴影的位置关系来确定黑洞的质量中心的位置及黑洞的旋转参量.     

Hawking radiation via tunneling from a <Emphasis Type="Italic">d</Emphasis>-dimensional black hole in Gauss–Bonnet gravity

We extend the Parikh–Wilczek method from Einstein gravity spacetime to Gauss–Bonnet modified gravity and study the tunneling radiation of particles across the event horizon of a d-dimensional Gauss–Bonnet Anti de-Sitter black hole. The emission rate of a particle is calculated. It is shown that the emission rate of massive particles takes the same functional form as that of massless particles although that their motion equations tunneling across the horizon are different. It is also shown that the emission spectrum deviates from the pure thermal spectrum but is consistent with an underlying unitary theory. In addition, significant but interesting phenomenon is demonstrated when Gauss–Bonnet term is present. The expression of the emission rate for a black hole in Gauss–Bonnet gravity differs from that for a black hole in Einstein gravity. After adopting the conventional tunneling rate, we obtain the expression of the entropy of the Gauss–Bonnet black hole, which is in accordance with the early results but does not obey the area law. So the research of tunneling radiation in this paper may serve as a new perspective of understanding the thermodynamics of black holes in Gauss–Bonnet gravity.     

On Born approximation in black hole scattering

A massless field propagating on spherically symmetric black hole metrics such as the Schwarzschild, Reissner–Nordström and Reissner–Nordström–de Sitter backgrounds is considered. In particular, explicit formulae in terms of transcendental functions for the scattering of massless scalar particles off black holes are derived within a Born approximation. It is shown that the conditions on the existence of the Born integral forbid a straightforward extraction of the quasi normal modes using the Born approximation for the scattering amplitude. Such a method has been used in literature. We suggest a novel, well defined method, to extract the large imaginary part of quasinormal modes via the Coulomb-like phase shift. Furthermore, we compare the numerically evaluated exact scattering amplitude with the Born one to find that the approximation is not very useful for the scattering of massless scalar, electromagnetic as well as gravitational waves from black holes.     

Constraints on Mass,Spin and Magnetic Field of Microquasar H 1743-322 from Observations of QPOs

The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in many microquasars can provide a powerful tool for testing of the phenomena occurring in strong gravity regime. QPOs phenomena can be well related to the oscillations of charged particles in accretion disks orbiting Kerr black holes immersed in external large-scalemagnetic fields. In the present paper we study the model ofmagnetic relativistic precession and provide estimations of the mass and spin of the central object of the microquasar H 1743-322 which is a candidate for a black hole. Moreover, we discuss the possible values of external magnetic field and study its influence on the motion of charged particles around rotating black hole.     

Gyroscope precession frequency analysis of a five-dimensional charged rotating Kaluza-Klein black hole

We study the spin precession frequency of a test gyroscope attached to a stationary observer in the five-dimensional rotating Kaluza-Klein black hole(RKKBH). We derive the conditions under which the test gyroscope moves along a timelike trajectory in this geometry, and the regions where the spin precession frequency diverges. The magnitude of the gyroscope precession frequency around the KK black hole diverges at two spatial locations outside the event horizon. However, in the static case, the behavior of the Lense-Thirring frequency of a gyroscope around the KK black hole is similar to the ordinary Schwarzschild black hole. Since a rotating Kaluza-Klein black hole is a generalization of the Kerr-Newman black hole, we present two mass-independent schemes to distinguish these two spacetimes.