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We show that the first several overtones could be calculated by the time-domain integration method for asymptotically de Sitter black holes already at the lowest multipole numbers of gravitational and electromagnetic perturbations. This is not possible for asymptotically flat black holes, for which extraction of frequencies with the Prony method is usually possible with reasonable accuracy only for the fundamental mode. The reason for much better efficiency in the de Sitter case is the absence of power-law tails: the quasinormal modes dominate the signal not only at the intermediate stage, but also at asymptotically late times. [ABSTRACT FROM AUTHOR]

We study the quasinormal modes, Hawking radiation and absorption cross-section of the Bardeen black hole surrounded by perfect fluid dark matter for a massless scalar field. Our results show that the oscillation frequency of quasinormal modes is enhanced as magnetic charge g or the dark matter parameter α increases. For damping rate of quasinormal modes, the influence of them is different. Specifically, the increase of dark matter parameter α makes the damping rate increasing at first and then decreasing. While the damping rate is continuously decreasing with the increase of the magnetic charge g. Moreover, we find that the increase of the dark matter parameter α enhances the power emission spectrum whereas magnetic charge g suppresses it. This means that the lifespan of black holes increases for smaller value of α and larger value of g when other parameters are fixed. Finally, the absorption cross-section of the considered black hole is calculated with the help of the partial wave approach. Our results suggest that the absorption cross-section decreases with the dark matter parameter α or the magnetic charge g increasing. [ABSTRACT FROM AUTHOR]

In this paper, we study the quasinormal modes for scalar, electromagnetic, and gravitational axial perturbations in the Hayward regular black hole surrounded by quintessence (HBH- ω q ). Using the third-order WKB approximation, we can determine the dependence of the quasinormal modes on the parameters of the regular black hole and the parameters on the test fields. We also determine the greybody factor, giving transmission and reflection coefficients of the scattered wave through the effective potentials in the WKB approximation using numerical analysis. [ABSTRACT FROM AUTHOR]

The Joule–Thomson effect and quasinormal modes (QNM) onto regular non-minimal magnetic charged black hole with a cosmological constant are being investigated. For this purpose, we extract some thermodynamical parameters such as pressure (P) and mass (M) in the presence of magnetic (Q m) as well as electric (q) charge. These parameters lead to inversion temperature (T i) , pressure (P i) and corresponding isenthalpic curves. We introduce the tortoise coordinate and the Klein–Gordon wave equation which leads to the second-order ordinary Schrödinger equation. We find out the complex frequencies of QNMs through the massless scalar field perturbation which satisfy boundary conditions by using the first-order Wentzel–Kramers–Brillouin (WKB) technique. [ABSTRACT FROM AUTHOR]

We find an exact black hole solution with a minimally coupled scalar field. The corresponding spacetime has two horizons and one of them is the black hole event horizon and the other is the cosmic horizon. In this sense, the solution is analogous to the Schwarzschild-de Sitter (or anti-de Sitter) spacetime. We investigate the thermodynamics and construct the first law of thermodynamics. At the same time, we make a study on the shadow and quasinormal modes of this black hole solution. [ABSTRACT FROM AUTHOR]

In this paper, we study the quasinormal modes of the massless Dirac field for charged black holes in Rastall gravity. The spherically symmetric black hole solutions in question are characterized by the presence of a power-Maxwell field, surrounded by the quintessence fluid. The calculations are carried out by employing the WKB approximations up to the 13th-order, as well as the matrix method. The temporal evolution of the quasinormal modes is investigated by using the finite difference method. Through numerical simulations, the properties of the quasinormal frequencies are analyzed, including those for the extremal black holes. Among others, we explore the case of a second type of extremal black holes regarding the Nariai solution, where the cosmical and event horizon coincide. The results obtained by the WKB approaches are found to be mostly consistent with those by the matrix method. It is observed that the magnitudes of both real and imaginary parts of the quasinormal frequencies increase with increasing κ , the spin–orbit quantum number. Also, the roles of the parameters Q and w , associated with the electric charge and the equation of state of the quintessence field, respectively, are investigated regarding their effects on the quasinormal frequencies. The magnitude of the electric charge is found to sensitively affect the time scale of the first stage of quasinormal oscillations, after which the temporal oscillations become stabilized. It is demonstrated that the black hole solutions for Rastall gravity in asymptotically flat spacetimes are equivalent to those in Einstein gravity, featured by different asymptotical spacetime properties. As one of its possible consequences, we also investigate the behavior of the late-time tails of quasinormal models in the present model. It is found that the asymptotical behavior of the late-time tails of quasinormal modes in Rastall theory is governed by the asymptotical properties of the spacetimes of their counterparts in Einstein gravity. [ABSTRACT FROM AUTHOR]

In this paper, a matrix method is employed to study the scalar quasinormal modes of Kerr as well as Kerr-Sen black holes. Discretization is applied to transfer the scalar perturbation equation into a matrix form eigenvalue problem, where the resulting radial and angular equations are derived by the method of separation of variables. The eigenvalues, quasinormal frequencies ω and angular quantum numbers λ, are then obtained by numerically solving the resultant homogeneous matrix equation. This work shows that the present approach is an accurate, as well as efficient method for investigating quasinormal modes. [ABSTRACT FROM AUTHOR]

We have studied quasinormal modes (QNMs) of spinor-, massless Dirac field perturbations of a black hole in massive gravity. The parameters of the theory, such as the mass of the black hole, the scalar charge of the black hole, mode number and the multipole number are varied to observe how the corresponding quasinormal frequencies change. We have also used the Pöschl-Teller approximation to reach analytical values for the frequencies of quasinormal modes for comparison with the numerically obtained values. Comparisons are done with the frequencies of the Schwarzschild black hole. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the area and mass spectrum of a Lifshitz black hole in 2+1 dimensions. This black hole is obtained for conformal gravity in 2+1 dimensions and is asymptotic to z = 0 Lifshitz spacetime. Quasinormal modes (QNM) frequencies of the conformally coupled scalar field perturbations are employed for the purpose of analyzing the area spectrum of the black hole. We have used two methods: modified Hod's conjecture and Kunsttater's method. In both methods, the area and the mass spectrum is shown to be equally spaced. We compared our results with the area spectrum of the BTZ black hole and the z = 3 black hole and made suggestions to extend this work in the future. [ABSTRACT FROM AUTHOR]

In this paper, we study the scalar and electromagnetic perturbations of an extended black hole in F(R) gravity. The quasinormal modes in two cases are evaluated and studied their behavior by plotting graphs in each case. To study the quasinormal mode, we use the third-order WKB method. The present study shows that the absolute value of imaginary part of complex quasinormal modes increases in both cases, thus the black hole is stable against these perturbations. As the mass of the scalar field increases the imaginary part of the frequency decreases. Thus, damping slows down with increasing mass of the scalar field. [ABSTRACT FROM AUTHOR]

Black hole thermodynamic stability can be determined by studying the nature of heat capacity of the system. For Schwarzschild black hole the heat capacity is negative, but in the quintessence field, this system shows a second-order phase transition, implying the existence of a stable phase. We further discuss the equation of state of the present system. While analyzing the quasinormal modes (QNM), we find that the massive scalar QNM frequencies in the complex ω plane shows a dramatic change when we plot it as a progressive function of quintessence state parameter. We also find the Hawking temperature of the system via the method of tunneling. [ABSTRACT FROM AUTHOR]

In this paper, we study the Dirac quasinormal modes of an uncharged 2+1 black hole proposed by Mandal et al. and referred to as MSW black hole. The quasinormal mode is studied using WKB approximation method. The study shows that the imaginary part of quasinormal frequencies increases indicating that the oscillations are damping and hence the black hole is stable against Dirac perturbations. [ABSTRACT FROM AUTHOR]

We investigated quasinormal frequencies (QNFs) in black brane with hyperscaling violating by using the continued fractions method. We calculate QNF of massless scalar field and electromagnetic field both with zero spatial momentum, find that QNFs have negative imaginary frequency suggesting black brane with hyperscaling violation is stable under those perturbations. [ABSTRACT FROM AUTHOR]

In this study, we employ the scalar perturbations of the charged dilaton black hole (CDBH) found by Chan, Home and Mann (CHM), and described with an action which emerges in the low-energy limit of the string theory. A CDBH is neither asymptotically flat (AF) nor non-asymptotically flat (NAF) spacetime. Depending on the value of its dilaton parameter a, it has both Schwarzschild and linear dilaton black hole (LDBH) limits. We compute the complex frequencies of the quasinormal modes (QNMs) of the CDBH by considering small perturbations around its horizon. By using the highly damped QNM in the process prescribed by Maggiore, we obtain the quantum entropy and area spectra of these black holes (BHs). Although the QNM frequencies are tuned by a, we show that the quantum spectra do not depend on a, and they are equally spaced. On the other hand, the obtained value of undetermined dimensionless constant e is the double of Bekenstein's result. The possible reason of this discrepancy is also discussed. [ABSTRACT FROM AUTHOR]

The area spectrum and entropy spectrum of the modified Schwarzschild black hole in gravity's rainbow are investigated via the quasinormal modes of the black hole. Using the modified Hod's method and Kunstatter's method that employ the proper frequency from the imaginary part other than the real part of the quasinormal modes, the area and entropy spacing of the black hole are calculated. The results obtained from these two methods agree with each other and the equally spaced area and entropy spectrum are derived. The obtained area and entropy spectrum are independent of the energies of test particles and are the same as from the usual Schwarzschild black hole. [ABSTRACT FROM AUTHOR]

Motivated by the new interpretation on quasinormal modes by Maggiore, we investigate the quantization of the extreme Reissner-Nordström black hole in the four-dimensional spacetime. Following Kunstatter's method, we derive the equally spaced area spectrum and the entropy, however the spacing differs from Setare's result via Hod's proposal. Moreover, our result is in full agreement with Bekenstein's result as well as the claim that black hole's area is equidistant in Einstein's Gravity theory by Wei et al. [ABSTRACT FROM AUTHOR]

In this paper we present the spectrum of entropy/area for Kehagias-Sfetsos (KS) black hole in Hořava-Lifshitz (HL) gravity via quasinormal modes (QNM) approach. We show that in the massive case, the mass parameter μ disappears in the entropy spectrum and the quasinormal modes are modified by a term proportional to the mass square term. Our calculations show that the charge-like parameter $\frac{1}{2\omega} = Q^{2}$ appears in the surface gravity and our calculations can be applied to any spherically symmetric spacetime which has only one physically acceptable horizon. Our main difference between our calculations and what was done in Ref. 1 is that we explicitly calculated the portion of charge and mass on the surface gravity and consequently in the QNM expression. Since the imaginary part of the QNM is related to the adiabatic invariance of the system and also to the entropy, surprisingly the mass parameter does not appear in the entropy spectrum. Our conclusion supported by some acclaims about the scalar field parameters (charges) cannot change the fundamental parameters in the four-dimensional black holes. [ABSTRACT FROM AUTHOR]

We study the quasinormal modes (QNMs) of charged braneworld black hole, which carry two types of "charge". In this paper, the six-order Wentzel-Kramers-Brillouin (WKB) approximation is applied to calculate the quasinormal frequencies (QNF), and then two types of charges affecting the shape of potential function, and oscillation frequency increases with increasing β while the damping of QMNs is slower as β is smaller. [ABSTRACT FROM AUTHOR]

The entropy and area spectra for D-dimensional Gauss–Bonnet black holes are investigated from two different approaches, which are the quasinormal modes approach developed by Hod, Kunstatter and Maggiore, and the very recent method proposed by Ropotenko. The two methods give the same results, which show that the entropy spectrum of Gauss–Bonnet black holes is equidistantly quantized with spacing ΔS = 2πℏ, while the area spectrum is not equally spaced. [ABSTRACT FROM AUTHOR]

The effect of cosmic string on the quasinormal modes (QNMs) of massless Dirac field perturbations were studied in different black hole spacetimes. Quasi-normal mode frequencies of massless Dirac field in Schwarzschild, RN extremal, SdS and near extremal SdS black hole spacetimes with cosmic string are obtained using WKB approximation. Our study shows a clear deviation in QNMs due to presence of cosmic string from those in the absence of string. The influence of cosmic string coded in the form of an increase in the oscillation frequency and damping time of QNMs. [ABSTRACT FROM AUTHOR]

We evaluate quasinormal mode frequencies for RN black hole spacetimes with cosmic string perturbed by a massless Dirac field, using Pöschl–Teller potential method. We find that only in the case of RN black hole having small charge, the effect due to cosmic string will dominate when perturbed by a negatively charged Dirac field, but if we are perturbing with positively charged Dirac field decay will be less in the case of black hole having cosmic string compared to the RN black hole without string. [ABSTRACT FROM AUTHOR]

Supersymmetry (SUSY) in quantum mechanics is extended from square integrable states to those satisfying the outgoing wave boundary condition. Using this formalism we obtain new exactly solvable potentials admitting quasinormal modes (QNM) solutions of the Klein–Gordon equation. [ABSTRACT FROM AUTHOR]

The quasinormal modes (QNMs) associated with the decay of massless arbitrary spin fields around a Schwarzschild black hole are investigated by using the continued fraction method in a united form and their universal properties are found. It is shown that these QNMs become evenly spaced for large angular quantum number l (for the boson perturbations) and j (for the fermion perturbations) and the spacing is given by $\Delta\omega=\frac{2}{3\sqrt{3}}-0.0000i$ which is independent of the spin number s and overtone number n, and in the complex plane they have an interesting trend which depends on n before they become the same value with the increasing l (or j). The distribution of the QNMs with arbitrary spin fields for large values l (or j) and small n can be expressed as $\omega_{n}\approx\frac{2}{3\sqrt{3}}[l({\rm or\,}\,j)+\frac{1}{2}-(n+\frac{1}{2})i]$. It is also shown that the angular quantum number has the surprising effect of increasing real part of the QNMs, but it almost does not affect the imaginary part, especially for the lowest lying mode. In addition, the spacing for imaginary part of the QNMs at high overtones is equidistant and equals to -i/4M, which is independent of l (or j) and s. [ABSTRACT FROM AUTHOR]

We study the sound perturbation of Unruh's acoustic geometry and present an exact expression for the quasinormal modes of this geometry. We found that the quasinormal frequencies are pure-imaginary which give a purely damped modes. [ABSTRACT FROM AUTHOR]

We study analytically the evolution of massless Dirac fields in the background of the Schwarzschild black hole. It is shown that although the quasinormal frequencies are the same for opposite chirality with the same |k|, we can differentiate neutrinos from anti-neutrinos in evolution of the massless Dirac fields provided we know both stages for the quasinormal modes and the power-law tail behavior since the decay rate of the neutrinos is described by t-(2|k|+1) while anti-neutrinos is t-(2|k|+3). [ABSTRACT FROM AUTHOR]

Motivated by the recent interest in quantization of black hole area spectrum, we consider the area spectrum of Kerr and extremal Kerr black holes. Based on the proposal by Bekenstein and others that the black hole area spectrum is discrete and equally spaced, we implement Kunstatter's method to derive the area spectrum for the Kerr and extremal Kerr black holes. The real part of the quasinormal frequencies of Kerr black hole used for this computation is of the form mΩ where Ω is the angular velocity of the black hole horizon. The resulting spectrum is discrete but not as expected uniformly spaced. Thus, we infer that the function describing the real part of quasinormal frequencies of Kerr black hole is not the correct one. This conclusion is in agreement with the numerical results for the highly damped quasinormal modes of Kerr black hole recently presented by Berti, Cardoso and Yoshida. On the contrary, extremal Kerr black hole is shown to have a discrete area spectrum which in addition is evenly spaced. The area spacing derived in our analysis for the extremal Kerr black hole area spectrum is not proportional to ln 3. Therefore, it does not give support to Hod's statement that the area spectrum $A_{n}=(4l^2_{p}\ln 3)n$ should be valid for a generic Kerr–Newman black hole. [ABSTRACT FROM AUTHOR]