Quasinormal modes of the BTZ black hole under scalar perturbations with a non-minimal coupling: exact spectrum

We perturb the non-rotating BTZ black hole with a non-minimally coupled massless scalar field, and we compute the quasinormal spectrum exactly. We solve the radial equation in terms of hypergeometric functions, and we obtain an analytical expression for the quasinormal frequencies. In addition, we compare our analytical results with the 6th order semi-analytical WKB method, and we find an excellent agreement. The impact of the nonminimal coupling as well as of the cosmological constant on the quasinormal spectrum is briefly discussed.     

Quasinormal modes of a two-dimensional black hole

For a two-dimensional black hole we determine the quasinormal frequencies of the Klein–Gordon and Dirac fields. In contrast to the well known examples whose spectrum of quasinormal frequencies is discrete, for this black hole we find a continuous spectrum of quasinormal frequencies, but there are unstable quasinormal modes. In the framework of the Hod and Maggiore proposals we also discuss the consequences of these results on the form of the entropy spectrum for the two-dimensional black hole.     

Quasinormal modes of the scalar field in five-dimensional Lovelock black hole spacetime

In this paper, using the third-order WKB approximation, we investigate the quasinormal frequencies of the scalar field in the background of a five-dimensional Lovelock black hole. We find that the ultraviolet correction to Einstein theory in the Lovelock theory makes the scalar field decay more slowly and oscillate more quickly, and the cosmological constant makes the scalar field decay more slowly and oscillate more slowly in the Lovelock black hole background.     

Quasinormal modes and absorption of a massless scalar field for the magnetic Gauss–Bonnet black hole

We study the massless scalar quasinormal frequencies of an asymptotically flat static and spherically symmetric black hole with a nonzero magnetic charge in four-dimensional extended scalar-tensor-Gauss–Bonnet theory. The results show that the real part of the quasinormal frequency becomes larger and the imaginary part becomes smaller with increasing the magnetic charge or the angular harmonic index. The existence of magnetic charges will reduce the damping of scalar perturbation, but increase the frequency. We also study the absorption cross-section of the scalar field in this black hole. We find that its curve will become lower as the magnetic charge increases, i.e. the magnetic charge will weaken the absorption capacity of the black hole. Meanwhile, the high-frequency limit of the total absorption cross-section is just the area of black hole shadow.     

Quasinormal oscillations and late-time tail of massless scalar perturbations of a magnetized black hole in Rastall gravity

In this study,we investigate the quasinormal mode and late-time tail of charged massless scalar perturbations of a black hole in generalized Rastall gravity.The black hole metric in question is spherically symmetric,accompanied by a power-Maxwell field surrounded by a quintessence fluid.We show that the massless scalar field,when dressed up with the magnetic field,acquires an effective mass,which significantly affects the properties of the resultant quasinormal oscillations and late-time tails.S...     

Quasinormal modes of a stationary axisymmetric EMDA black hole

The massless scalar quasinormal modes (QNMs) of a stationary axisymmetric Einstein--Maxwell dilaton--axion (EMDA) black hole are calculated numerically using the continued fraction method first proposed by Leaver. The fundamental quasinormal frequencies (slowly damped QNMs) are obtained and the peculiar behaviours of them are studied. It is shown that these frequencies depend on the dilaton parameter $D$, the rotational parameter $a$, the multiple moment $l$ and the azimuthal number $m$, and have the same values with other authors at the Schwarzschild and Kerr limit.     

Quasinormal modes in the background of charged Kaluza–Klein black hole with squashed horizons

We study the scalar perturbation in the background of the charged Kaluza–Klein black holes with squashed horizons. We find that the position of infinite discontinuities of the heat capacities can be reflected in quasinormal spectrum. This shows the possible non-trivial relation between the thermodynamical and dynamical properties of black holes.     

Quasinormal modes of a Schwarzschild black hole surrounded by free static spherically symmetric quintessence: electromagnetic perturbations

In this paper, we evaluated the quasinormal modes of electromagnetic perturbation in a Schwarzschild black hole surrounded by the static spherically symmetric quintessence by using the third-order WKB approximation when the quintessential state parameter w _q in the range of −1/3 < w _q < 0. Due to the presence of quintessence, Maxwell field damps more slowly. And when at −1 < w _q < −1/3, it is similar to the black hole solution in the ds/Ads spacetime. The appropriate boundary conditions need to be modified.     

Quasinormal modes of charged black holes in Einstein-Maxwell-Weyl gravity

We study quasinormal modes(QNMs)of charged black holes in the Einstein-Maxwell-Weyl(EMW)gravity by adopting the test scalar field perturbation.We find that the imaginary part of QNM frequencies is consistently negative for different angular parameters l,indicating that these modes always decay and are therefore stable.We do not observe a linear relationship between the QNM frequencyωand parameter p for these black holes,as their charge Q causes a nonlinear effect.We evaluate the massive scalar field perturbation in charged black holes and find that random long lived modes(i.e.,quasiresonances)could exist in this spectrum.     

Instabilities of massive scalar perturbations of a rotating black hole

We study the stability of a massive scalar field in the exterior metric of a rotating Kerr black hole. An argument based on energy conservation shows, under some strong technical assumptions, that unstable normal modes exist. These unstable modes can be interpreted as wave packets in bound, superradiant orbits. A JWKB estimate of the fastest growth rate gives 10^?7M^?1exp(?1.84Mμ) in the case Mμ ? 1, where M is the mass of the hole and μ is the mass of the field. The existence of unstable normal modes has significant implications for quantum particle creation by rotating black holes, which we attempt to assess.     

Solution of Dirac equation around a charged rotating black hole

The aim of this paper is to solve the radial parts of a Dirac equation in Kerr-Newman （KN） geometry. The potential is replaced by a collection of step functions, then the reflection and transmission coefficients as well as the solution of the wave equation are obtained by using a quantum mechanical method. The result shows that the waves with different values of mass will be scatted off very differently.     

Quasinormal modes of a Schwarzschild black hole immersed in an electromagnetic universe

We study the quasinormal modes(QNMs) of a Schwarzschild black hole immersed in an electromagnetic(EM) universe. The immersed Schwarzschild black hole(ISBH) originates from the metric of colliding EM waves with double polarization [Class. Quantum Grav. 12, 3013(1995)]. The perturbation equations of the scalar fields for the ISBH geometry are written in the form of separable equations. We show that these equations can be transformed to the confluent Heun's equations, for which we are able to use known techniques to perform analytical quasinormal(QNM) analysis of the solutions. Furthermore, we employ numerical methods(Mashhoon and 6~(th)-order Wentzel-Kramers-Brillouin(WKB)) to derive the QNMs. The results obtained are discussed and depicted with the appropriate plots.     

Absorption of massive scalar field by a charged black hole

Absorption and reflection of charged, massive scalar field by the Reisner-Nordstrom black hole are investigated through a numerical computation. The absorption is suppressed when (Schwarzschild radius) < (Compton wave length) and the amplification of the wave occurs when the level crossing condition is satisfied.     

Dirac quasinormal modes of Born-Infeld black hole spacetimes

Quasinormal modes (QNMs) for massless and massive Dirac perturbations of Born-Infeld black holes (BHs) in higher dimensions are investigated. Solving the corresponding master equation in accordance with hypergeometric functions and the QNMs are evaluated. We discuss the relationships between QNM frequencies and spacetime dimensions. Meanwhile, we also discuss the stability of the Born-Infeld BH by calculating the temporal evolution of the perturbation field. Both the perturbation frequencies and the decay rate increase with increasing dimension of spacetime n. This shows that the Born-Infeld BHs become more and more unstable at higher dimensions. Furthermore, the traditional finite difference method is improved, so that it can be used to calculate the massive Dirac field. We also elucidate the dynamic evolution of Born-Infeld BHs in a massive Dirac field. Because the number of extra dimensions is related to the string scale, there is a relationship between the spacetime dimension n and the properties of Born-Infeld BHs that might be advantageous for the development of extra-dimensional brane worlds and string theory.     

Hawking radiation of scalar and Dirac quanta from a Kerr black hole

Unruh’s technique of replacing collapse by boundary conditions on the past horizon (theξ-quantisation scheme) for the derivation of the well-known Hawking radiation is extended to the Kerr black hole for the scalar and especially for the spin half field. The expectation value of the energy momentum tensor is evaluated asymptotically in theξ-vacuum state yielding explicitly the net Hawking flux of scalar and spin half quanta. The appropriate statistical distribution that emerges naturally for Dirac quanta validates the ξ-scheme for fermions and confirms the association of temperature with a Kerr black hole.