Stellar Rotating Black Holes

Both mass and charge are needed to create a rotating Black Hole as has been investigated in great mathematical detail by the Reissner-Nordstrom metric and the Kerr-Newman metric. It is their application to astronomical phenomena that they have stated difficulty with because astronomical objects have no net electric charge and that is what we are exploring. While the energy in the gravitational field of the mass of a Neutron Star alone cannot create a stationary Black Hole, together with the energy in the strong magnetic field created by a rotating Neutron Star a rotating Black Hole is formed. Black Holes are the portal to the next higher spatial dimension.

Discussion on event horizon and quantum ergosphere of dynamic rotating black holes in a tunneling framework

According to the Parikh-Wilczek tunneling framework, the locations of the local horizons of dynamic rotating black holes can be worked out. The calculations show that the quantum ergosphere of the black hole is identical with the tunneling potential barrier set by particle＇s tunneling across the relevant horizon. Then, some discussions on the origin of the Hawking radiation will be shown.

Discussion on event horizon and quantum ergosphere of dynamic rotating black holes in a tunneling framework

According to the Parikh–Wilczek tunneling framework, the locations of the local horizons of dynamic rotating black holes can be worked out. The calculations show that the quantum ergosphere of the black hole is identical with the tunneling potential barrier set by particle’s tunneling across the relevant horizon. Then, some discussions on the origin of the Hawking radiation will be shown.

Observational signatures of rotating black holes in the semiclassical gravity with trace anomaly

In a recent work by Fernandes[Phys.Rev.D 108(6),L061502(2023)],an exact stationary and axisymmetric solution was discovered in semiclassical gravity with type-A trace anomaly.This was identified as a quantum-corrected version of the Kerr black hole.In this study,we explore the observational signatures of this black hole solution.Our investigation reveals that prograde and retrograde light rings exist,whose radii increase monotonically with the coupling parameterα.Whenαis negative,the shadow area for the quantum-corrected black hole is smaller than that of the Kerr black hole,whereas whenαis positive,the area is larger.For a near-extremal black hole,its high-spin feature(the NHEKline)is found to be highly susceptible to disruption byα.Furthermore,we discuss the images of the quantum-corrected black hole in the presence of a thin accretion disk and compare them to those of the Kerr black hole.Our study highlights the importance of near-horizon emission sources in detecting the effects of quantum corrections by black hole images.

Effect of nonlinear electrodynamics on shadows of slowly rotating black holes

In this study,we investigate the effect of nonlinear electrodynamics on the shadows of charged,slowly rotating black holes with the presence of a cosmological constant.Rather than the null geodesic of the background black hole spacetime,the trajectory of a photon,as a perturbation of the nonlinear electrodynamic field,is governed by an effective metric.The latter can be derived by analyzing the propagation of a discontinuity of the electromagnetic waveform.Subsequently,the image of the black hole and its shadow can be evaluated using the backward raytracing technique.We explore the properties of the resultant black hole shadows of two different scenarios of nonlinear electrodynamics,namely,the logarithmic and exponential forms.In particular,the effects of nonlinear electrodynamics on the optical image are investigated,as well as the image s dependence on other metric parameters,such as the black hole spin and charge.The resulting black hole image and shadow display rich features that potentially lead to observational implic ations.

Shadows of magnetically charged rotating black holes surrounded by quintessence

In this work,we study the optical properties of a class of magnetically charged rotating black hole spacetimes.The black holes in question are assumed to be immersed in the quintessence field,and subsequently,the resulting black hole shadows are expected to be modified by the presence of dark energy.We investigate the photon region and the black hole shadow,especially their dependence on the relevant physical conditions,such as the quintessence state parameter,angular momentum,and magnetic charge magnitude.The photon regions depend sensitively on the horizon structure and possess intricate features.Moreover,from the viewpoint of a static observer,we explore a few observables,especially those associated with the distortion of the observed black hole shadows.

Charged Fermions Tunneling from a Rotating Charged Black Hole in 5-Dimensional Gauged Supergravity

Recent research shows that Hawking radiation from black hole horizon can be treated as a quantum tunneling process, and fermions tunneling method can successfully recover Hawking temperature. In this tunneling framework, choosing a set of appropriate matrices γ^μ is an important technique for fermions tunneling method. In this paper, motivated by Kerner and Man＇s fermions tunneling method of 4 dimension black holes, we further improve the analysis to investigate Hawking tunneling radiation from a rotating charged black hole in 5-dimensional gauged supergravity by constructing a set of appropriate matrices γ^μ for general covariant Dirac equation. Finally, the expected Hawking temperature of the black hole is correctly recovered, which takes the same form as that obtained by other methods. This method is universal, and can also be directly extend to the other different-type 5-dimensional charged black holes.

On Hawking Radiation of 3D Rotating Hairy Black Holes

We study the Hawking radiation of 3D rotating hairy black holes. Specifically, we compute the transition probability of bosonic and fermionic particles in such backgrounds. Then, we show that the transition probability is independent of the nature of the particle. It is observed that the charge of the scalar hairy B and the rotation parameter a control such a probability.

Exploring the shadow of a rotating charged ModMax black hole

The research presented in this paper discusses the impact that the parameters of charge(Q)and screening factor(γ)have on properties of the horizon and silhouette of rotating charged Mod Max black holes which were reviewed in[Eur.Phys.J.C(2022)82:1155]recently,building upon previous findings in the field.Furthermore,the study explores the behavior of null geodesics,which can help us better understand the apparent shape of the black hole’s silhouette,as well as the distortion parameter and approximate radii of the silhouette that are influenced by the aforementioned parameters,and there are some values of parameter Q which corresponds to data from the Event Horizon Telescope(EHT).Notably,we explore the distortion parameter and approximate radii of the silhouette,revealing that while an increase inγleads to a growth in silhouette radius(Rs),it simultaneously reduces the distortion rate(δs).Conversely,heightened Q charge results in a reduction of Rsaccompanied by an increase inδs.Lastly,the paper analyzes the effects of the black hole’s parameters on the effective potential and energy emission:the peak value of the energy emission rate experiences a decrease as the screening factor(γ)increases,while it increases with higher values of the charge parameter(Q).

Preliminary analyses of the dynamics and thermodynamics of rotating regular black holes

We investigate the dynamic and thermodynamic laws governing rotating regular black holes.By analyzing dynamic properties,i.e.,the interaction between scalar particles and rotating regular black holes,we establish the criteria that determine whether such black holes satisfy the laws of thermodynamics.In addition,we provide the general form of conserved quantities related to rotating regular black holes,including the relevant flows associated with neutral scalar particles.Meanwhile,we reexamine the relationship between the third law of thermodynamics and weak cosmic censorship conjecture for rotating regular black holes.Based on the abovementioned criteria,we discuss the laws of thermodynamics for three models of rotating regular black holes:Rotating Hayward black holes,Kerr black-bounce solutions,and loop quantum gravity black holes.Our findings indicate that none of the three models satisfies the first law of thermodynamics.In particular,the first and third models fail to comply with the three laws of thermodynamics,whereas the second model satisfies only the second and third laws of thermodynamics.Finally,we attempt to rescue the laws of thermodynamics by modifying entropy or extending the phase space.However,the two scenarios cannot ensure the three laws of thermodynamics in the three models,which reveals an unusual property of rotating regular black holes.

Spectroscopy via adiabatic covariant action for the Baados-Teitelboim-Zanelli (BTZ) black hole

Very recently, via the covariant form of the adiabatic invariant I = ∮pidqi instead of I = ∮pidqi, an equally spaced spectroscopy of a Schwarzschild black hole was derived. The emphasis was given to the covariant of results. In this paper, we extend that work in a spherically symmetric spacetime to the case of a rotating Bafiados-Teitelboim-Zanelli （BTZ） black hole. It is noteworthy that the adiabatic covariant action I = ∮pidqi gives the same value for the black hole spectroscopy in different coordinates. The result shows that the area spectrum is △A = 8πl2p, which confirms Bekenstein＇s initial proposal. And the result is consistent with that already obtained by other methods.

Superradiance of massive scalar particles around rotating regular black holes

Regular black holes,as part of an important attempt to eliminate the singularities in general relativity,have been of wide concern.Because the superradiance associated with rotating regular black holes plays an indispensable role in black hole physics,we calculate the superradiance related effects,i.e.,the superradiance instability and the energy extraction efficiency,for a scalar particle with a small mass around a rotating regular black hole,where the rotating regular black hole is constructed by the modified Newman-Janis algorithm.We analytically give the eigenfrequency associated with instability and the amplification factor associated with energy extraction.For two specific models,i.e.,the rotating Hayward and Bardeen black holes,we investigate how their regularization parameters affect the growth of instability and the efficiency of energy extraction from the two rotating regular black holes.We find that the regularization parameters give rise to different modes of the superradiance instability and the energy extraction when the rotation parameters vary.There are two modes for the growth of superradiance instability and four modes for the energy extraction.Our results show the diversity of superradiance in the competition between the regularization parameter and the rotation parameter for rotating regular black holes.

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.

Novel Rotating Hairy Black Hole in (2 + 1) Dimensions

We present some novel rotating hairy black hole metric in （2 ＋ 1） dimensions, which is an exact solution to the field equations of the Einstein-scalar-AdS theory with a non-minimal coupling. The scalar potential is determined by the metric ansatz and consistency of the field equations and cannot be prescribed arbitrarily. In the simplified, critical ease, the scalar potential contains two independent constant parameters, which are respectively related to the mass and angular momentum of the black hole in a particular way. As long as the angular momentum does not vanish, the metric can have zero, one or two horizons. The case with no horizon is physically uninteresting because of the curvature singularity lying at the origin. We identify the necessary conditions for at least one horizon to be present in the solution, which imposes some bound on the mass-angular momentum ratio. For some particular choice of pararneters our solution degenerates into some previously known black hole solutions.

Radiation spectrum of rotating Gdel black hole and correction entropy

We study the Hawking radiation of the scalar field in the rotating Gdel black hole in minimal five-dimensional supergravity. We not only derive radiation spectra that satisfy the unitary principle but also obtain the correction term of Bekenstein-Hawking entropy. The conclusion will help us learn more about the rotating Gdel black hole in minimal five-dimensional supergravity. This provides a greater understanding of the thermal radiation of black holes.

Spectroscopy of the rotating BTZ black hole via adiabatic invariance

According to Bohr-Sommerfeld quantization rule,an equally spaced horizon area spectrum of a static,spherically symmetric black hole was obtained under an adiabatic invariant action.This method can be extended to the rotating black holes.As an example,this method is applied to the rotating BTZ black hole and the quantized spectrum of the horizon area is obtained.It is shown that the area spectrum of the rotating BTZ black hole is also equally spaced and irrelevant to the rotating parameter,which is consistent with the Bekenstein conjecture.Specifically,the derivation does not need the quasinormal frequencies and the small angular momentum limit.

Massive Vector Particles Tunneling from the Neutral Rotating Anti-de Sitter Black Holes in Conformal Gravity

We investigate the massive vector particles' Hawking radiation from the neutral rotating Anti-de Sitter(AdS) black holes in conformal gravity by using the tunneling method.It is well known that the dynamics of massive vector particles are governed by the Proca field equation.Applying WKB approximation to the Proca equation,the tunneling probabilities and radiation spectrums of the emitted particles are derived.Hawking temperature of the neutral rotating AdS black holes in conformal gravity is recovered,which is consistent with the previous result in the literature.

Integral Equations for the Spin-Weighted Spheroidal Wave Functions

We present new integral equations for the spin-weighted spheroidal wave functions which in turn should lead to global uniform estimates and should help in particular in the study of their dependence on the parameters. For the prolate spheroidal wavefunction with m=0, there exists the integral equation whose kernel is （sin x）/x, and the sinc function kernel （sin x）/x is of great mathematical significance. We also extend the similar sinc function kernel （sin x）/x to the case m≠0 and s≠0, which interestingly turn out as some kind of Hankel transformations.