Object Picture of Quasinormal Modes for Stringy Black Holes

We study the quasinormal modes （QNMs） for stringy black holes. By using numerical calculation, the relations between the QNMs and the parameters of black holes are minutely shown. For （1＋1）-dimensional stringy black hole, the real part of the quasinormal frequency increases and the imaginary part of the quasinormal frequency decreases as the mass of the black hole increases. Furthermore, the dependence of the QNMs on the charge of the black hole and the flatness parameter is also illustrated. For （1＋3）-dimensional stringy black hole, increasing either the event horizon or the multipole index, the real part of the quasinormal frequency decreases. The imaginary part of the quasinormal frequency increases no matter whether the event horizon is increased or the multipole index is decreased.     

Asymptotic Quasinormal Modes of the Garfinkle-Horowitz-Strominger Dilaton Black Hole

Using the monodromy technique proposed by Motl and Neitzke (.Adv. Theor. Math. Phys. 7(2003)307), we investigate the analytic forms of the asymptotic quasinormal frequencies for the massless scalar perturbation in the Garfinkle-Horowitz-Strominger dilaton spacetime. We find that the real parts of the quasinormal frequencies are TH ln 3. This agrees with that of the quasinormal modes in the Schwarzschild spacetime. Our result implies that Hod‘s conjecture about In 3 is still valid for the black hole spacetime in the string theory.     

Dirac Quasinormal Modes of a Schwarzschild Black Hole surrounded by Free Static Spherically Symmetric Quintessence

We evaluate the quasinormal modes of massless Dirac perturbation in a Schwarzschild black hole surrounded by the free static spherically symmetric quintessence using the third-order Wentzel-Kramers-Brillouin （WKB） approximation. The result shows that the massless Dirac field damps more slowly due to the presence of quintessence. The real part of the quasinormal modes increases and the absolute value of the imaginary part increases when the state parameter wq increases. In other words, the massless Dirac field decays more rapidly for the larger Wq. The peak value of potential barrier becomes higher as ｜k｜ increases and the location of peak moves along the right for fixed wq.     

Quasinormal Modes of Electromagnetic Perturbation around a Stringy Black Hole

We investigate the electromagnetic perturbation around a stringy black hole. A second-order differential equation is obtained for the perturbation. The variation of the effective potential with r is presented. The complex frequencies of the quasinormal modes of electromagnetic perturbation around a stringy black hole are computed by the third Wentzel-Kramers-Brillouin （WKB） approximation. The results show that the parameters resulted from the compactification of higher dimensions can influence the quasinormal complex frequencies, and the Maxwell field around a stringy black hole damps more slowly than that around a Schwarzschild black hole.     

Quasinormal Modes of a Noncommutative-Geometry-Inspired Schwarzschild Black Hole: Gravitational,Electromagnetic and Massless Dirac Perturbations

In our previous work [Chin. Phys. Lett. 35(2018) 010410], the quasinormal modes of massless scalar field perturbation in a noncommutative-geometry-inspired Schwarzschild black hole spacetime are studied using the third-order Wentzel–Kramers–Brillouin approximative approach. In this study, we extend the work to the cases of gravitational, electromagnetic and massless Dirac perturbations. The result further confirms that the noncommutative parameter plays an important role for the quasinormal frequencies.     

Quasinormal Spectrum and Quantization of the Kerr--Newman Black Hole

The intermediate asymptotic quasinormal mode spectrum of the charged scalar and Dirac fields in the near extremal Kerr-Newman black hole is studied analytically, It is found that the quasinormal mode spectrum can be expressed in terms of the Hawking temperature Thb, the electric potential Ф＋ and the horizon＇s angular velocity ΩH for the case of （eФ_ ＋ mΩH） 〉 （1 - 4πThb）Re（ω） （where e is the charge and m is the azimuthal projection number）, whereas it is only relevant to the charge and the mass parameter for another case. It is also shown that by using the Bohr＇s correspondence principle, the fundamental change in the black-hole surface area induced by the emission of a rotating charged quantum from the Kerr-Newman black hole is in accord with the Bekenstein-Mukhanov general prediction.     

Bosonic and fermionic entropy of black holes with different temperatures on horizon surface

By using the method of quantum statistics, we derive directly the partition functions of bosonic and fermionic field in the black hole space－time with different temperatures on horizon surface. The statistical entropy of the black hole is obtained by an improved brick-wall method. When we choose a proper parameter in our results, we can obtain that the entropy of the black hole is proportional to the area of horizon. In our result, there do not exist any neglected term or divergent logarithmic term as given in the original brick-wall method. We have avoided the difficulty in solving the wave equation of the scalar and Dirac field. A simple and direct way of studying entropy of the black hole is given.     

Black Hole Entropy with Modified Dispersion Relations

There is much interest in resolving the quantum corrections to Bekenstein-Hawking entropy with a large length scale limit. The leading correction term ＆ given by the logarithm of black hole area with a model-dependent coefficient. Recently the research for quantum gravity implies the emergence of a modification of the energy-momentum dispersion relation （MDR）, which plays an important role in the modified black hole thermodynamics. In this paper, we investigate the quantum corrections to Bekenstein-Hawking entropy in four-dimensional Sehwarzschild black hole and Reissner-Nordstrom black hole respectively based on MDR.     

Late-Time Evolution of the Phantom Scalar Perturbation in the Background of a Spherically Symmetric Static Black Hole

The late-time evolution of the phantom scalar perturbation is investigated in the spacetime of a four-dimensionai spherically symmetric static black hole. It is revealed that the asymptotic tail of the phantom scalar field is dominated by the growth behavior t-（l＋3/2）eμt, which depends on the multipole moment l and the field moss but is independent of the mass M and charge Q of the black hole. This growth behavior is in strong contrast to the decaying tall of the usual massive scalar perturbation and shows that the external phantom scalar perturbation is unstable in the spherically symmetric static black hole spacetime.     

Area spectra of BTZ black holes via periodicity

Motivated by the recent work that the periodicity of a black hole is responsible for the area spectrum,we exclusively utilize the period of motion of an outgoing wave,which is shown to be related to the vibrational frequency of the perturbed black hole,to study area spectra of a non-rotating BTZ black hole and a rotating BTZ black hole.It is found that the area spectra and entropy spectra for both space times are equally spaced.In addition,we find that though the entropy spectra of the 3-dimensional BTZ black holes take the same form as those of the 4-dimensional black holes,the area spectra depend on the dimension of space times.Our result confirms that the entropy spectrum of a black hole is more fundamental than the area spectrum.     

Quasinormal Modes for Electromagnetic Field Perturbation of the Asymptotic Safe Black Hole

In this paper, the quasinormal modes (QNMs) of electromagnetic field perturbation to asymptotic safe (AS) black hole are discussed. Through six-order WKB approach we investigate the effects of quantum correction to the quasinormal modes (QNMs) numerically. Meanwhile by means of finite difference method, the evolutions of such perturbation to the safe black hole are figured out with corresponding parameters. It is found that the stability of black hole remains although the decay frequency and damping speed of oscillations are respectively increased and lowered by the quantum correction to classic Schwarzschild black hole.     

Quasinormal Modes of Spherically Symmetric Curve Spacetime with Dark Matter Term

We study quasinormal modes of scalar field perturbation and electromagnetic field perturbation in a black hole space-time with dark matter by using WKB approximation method. The result shows clearly that the real part of black hole quasinormal modes is mainly determined by angular quantum number while its imaginary part mainly determined by model number. We also found out that the dark matter will restrain the perturbation frequency and slow down the speed of damping in spacetime. In addition; dark matter has a greater influence upon quasinormal modes in the electromagnetic field than that in the scalar field.     

Quasinormal Modes in Double-Charge de Sitter Black Hole

The black hole, as a hot topic to be regarded as a normally research to become a strong evidence for its existence, made more and more people get involved in its research. To calculating the quasinormal modes for massless scalar field and Maxwell’s field in double-charge de Sitter black hole by using WKB approximation method, there is a fact that the speed of weakening electromagnetic perturbation will be reduced. The quasinormal modes in black hole mainly depends on angular quantum number l when its real part is in lower-frequency circumstances. At the same time, imaginary part mainly depends on the overtone number n. When the black hole carries the same electronic quantity, the more the electronic charges have, the smaller the real part and imaginary part of quasinormal modes will be.     

Quasinormal Modes of the Planar Black Holes of a Particular Lovelock Theory

In this work, we study the scalar quasinormal modes of a planar black hole metric in asymptotic anti-de Sitter spacetime derived from a particular Lovelock theory. The quasinormal frequencies are evaluated by adopting the Horowitz-Hubeny method as well as a matrix formalism. Also, the temporal evolution of small perturbations is studied by using finite difference method. The roles of the dimension of the spacetime, the parameter of the metric k, as well as the temperature of the background black hole, are discussed. It is observed that the particular form of the metric leads to quasinormal frequencies whose real parts are numerically insignificant. The black hole metric is found to be stable against small scalar perturbations.     

Quasinormal Modes of Clifton–Barrow Black Holes

In this paper, we study the theoretical quasinormal modes produced by scalar perturbations around a static, spherically symmetric black hole with exterior metric described by the Clifton–Barrow solution of R ^1+δ gravity. It is found that the δ-correction increases both the real and imaginary part of the quasinormal frequency. Compared with those of ordinary Schwarzschild black hole with the same size, the oscillating quasi-period of scalar perturbation of Clifton–Barrow black hole is remarkably short for the case of low multi-pole quantum number l, while the difference of the damping time scales is slight. However, in the large l limit, the relative differences of both real and imaginary part of quasinormal modes have the same amplitude.     

Quasinormal Modes of Charged Dilaton Black Holes in 2 + 1 Dimensions

We have studied the scalar perturbation of static charged dilaton black holes in 2 + 1 dimensions. The black hole considered here is a solution to the low-energy string theory in 2 + 1 dimensions. It is asymptotic to the anti-de Sitter space. The exact values of quasinormal modes for the scalar perturbations are calculated. For both the charged and uncharged cases, the quasinormal frequencies are pure-imaginary leading to purely damped modes for the perturbations.     

Gravitational Perturbation of Garfinkle-Horowitz-Strominger Dilaton Black Hole and Quasinormal Modes

We research gravitational perturbation of Garfinkle-Horowitz-Strominger dilaton black hole and its quasinormal modes by using WKB approach proposed by Schutz, Will, Iyer and Konoplya. The quasinormal frequency with different angular momentum l is calculated in this paper. Our results show that, as the charge parameter b increase, both the real part and the absolute value of imaginary part of quasinormal frequency also increase, which means that the effect of charge in Garfinkle-Horowitz-Strominger dilaton background spacetime lead to higher frequency gravitational wave and the quasinormal modes damp at a rapider rate.     

Electromagnetic Quasinormal Modes in Hořava-Lifshitz Gravity

The electromagnetic quasinormal modes of Ho?ava-Lifshitz black hole is investigated by means of six-order WKB approach. We in this paper compare the quasinormal modes of this black hole with the charged black hole’s cases (we here take a regular charged black hole and Reissner-Nordström black hole for example). The numerical results of Ho?ava-Lifshitz’s quasinormal modes frequency show that the absolute value of imaginary part decrease as the parameter α increase. The fact means that charge in this spacetime make the quasinormal modes damp at a slower rate.     

Area spectra of extreme Kerr and nearly extreme Kerr–Newmann black holes from quasinormal modes

The area spectra of extreme Kerr and nearly extreme Kerr–Newmann black holes are investigated from quasinormal modes via Maggiore’s physical interpretation of quasinormal modes. Using the first law of black hole thermodynamics and the action variable quantization, we arrive at consistent equally spaced area and entropy spectra. Results show that the spectra are irrelevant to the parameters of the black holes and the perturbation fields, which fully agree with Bekensteins original conjecture. In the calculations, we have defined the corresponding Hawking temperatures of the black holes following the suggestion of Mäkelä et al. to avoid the zero temperature and to guarantee the (nearly-) extreme black holes quantizable.     

Quasinormal Modes of a Noncommutative-Geometry-Inspired Schwarzschild Black Hole

The quasinormal modes(QNMs) of massless scalar field perturbation in a noncommutative-geometry-inspired Schwarzschild black hole spacetime are studied using the third-order Wentzel-Kramers-Brillouin approximative approach. The result shows that the noncommutative parameter plays an important role for the quasinormal(QNM) frequencies.