scholarly journals Quasinormal modes of hot, cold and bald Einstein–Maxwell-scalar black holes

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Jose Luis Blázquez-Salcedo ◽  
Carlos A. R. Herdeiro ◽  
Sarah Kahlen ◽  
Jutta Kunz ◽  
Alexandre M. Pombo ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Unstable Mode ◽  
Quasinormal Modes ◽  
Coupling Function ◽  
Quartic Coupling ◽  
Linear Mode ◽  
Mode Stability ◽  
Black Hole Solutions

AbstractEinstein–Maxwell-scalar models allow for different classes of black hole solutions, depending on the non-minimal coupling function $$f(\phi )$$ f ( ϕ ) employed, between the scalar field and the Maxwell invariant. Here, we address the linear mode stability of the black hole solutions obtained recently for a quartic coupling function, $$f(\phi )=1+\alpha \phi ^4$$ f ( ϕ ) = 1 + α ϕ 4 (Blázquez-Salcedo et al. in Phys. Lett. B 806:135493, 2020). Besides the bald Reissner–Nordström solutions, this coupling allows for two branches of scalarized black holes, termed cold and hot, respectively. For these three branches of black holes we calculate the spectrum of quasinormal modes. It consists of polar scalar-led modes, polar and axial electromagnetic-led modes, and polar and axial gravitational-led modes. We demonstrate that the only unstable mode present is the radial scalar-led mode of the cold branch. Consequently, the bald Reissner–Nordström branch and the hot scalarized branch are both mode-stable. The non-trivial scalar field in the scalarized background solutions leads to the breaking of the degeneracy between axial and polar modes present for Reissner–Nordström solutions. This isospectrality is only slightly broken on the cold branch, but it is strongly broken on the hot branch.

scholarly journals Scalar modes, spontaneous scalarization and circular null-geodesics of black holes in scalar-Gauss–Bonnet gravity

2020 ◽  
Vol 29 (11) ◽  
pp. 2041006 ◽  
Author(s):  
Caio F. B. Macedo
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Scalar Field ◽  
Quasinormal Modes ◽  
Mode Analysis ◽  
Bonnet Gravity ◽  
Black Hole Binaries ◽  
The Impact ◽  
Black Hole Solutions

In general relativity, astrophysical black holes (BHs) are simple objects, described by just their mass and spin. These simple solutions are not exclusive to general relativity, as they also appear in theories that allow for an extra scalar degree of freedom. Recently, it was shown that some theories which couple a scalar field with the Gauss–Bonnet invariant can have the same classic black hole solutions from general relativity as well as hairy BHs. These scalarized solutions can be stable, having an additional “charge” term that has an impact on the gravitational-wave emission by black hole binaries. In this paper, we overview black hole solutions in scalar-Gauss–Bonnet gravity, considering self-interacting terms for the scalar field. We present the mode analysis for the monopolar and dipolar perturbations around the Schwarzschild black hole in scalar-Gauss–Bonnet, showing the transition between stable and unstable solutions. We also present the time-evolution of scalar Gaussian wave packets, analyzing the impact of the scalar-Gauss–Bonnet term in their evolution. We then present some scalarized solutions, showing that nonlinear coupling functions and self-interacting terms can stabilize them. Finally, we compute the light-ring frequency and the Lyapunov exponent, which possibly estimate the black hole quasinormal modes in the eikonal limit.

scholarly journals Spinning boson stars and hairy black holes with nonminimal coupling

2018 ◽  
Vol 27 (11) ◽  
pp. 1843009 ◽  
Author(s):  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Coupling Parameter ◽  
Nonminimal Coupling ◽  
Boson Stars ◽  
Hairy Black Holes ◽  
Black Hole Solutions ◽  
Hairy Black Hole ◽  
Coupled Theory

We obtain spinning boson star solutions and hairy black holes with synchronized hair in the Einstein–Klein–Gordon model, wherein the scalar field is massive, complex and with a nonminimal coupling to the Ricci scalar. The existence of these hairy black holes in this model provides yet another manifestation of the universality of the synchronization mechanism to endow spinning black holes with hair. We study the variation of the physical properties of the boson stars and hairy black holes with the coupling parameter between the scalar field and the curvature, showing that they are, qualitatively, identical to those in the minimally coupled case. By discussing the conformal transformation to the Einstein frame, we argue that the solutions herein provide new rotating boson star and hairy black hole solutions in the minimally coupled theory, with a particular potential, and that no spherically symmetric hairy black hole solutions exist in the nonminimally coupled theory, under a condition of conformal regularity.

scholarly journals Deforming charged black holes with dipolar differential rotation boundary

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Tong-Tong Hu ◽  
Shuo Sun ◽  
Hong-Bo Li ◽  
Yong-Qiang Wang
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Chemical Potential ◽  
Dimensional Space ◽  
Quasinormal Modes ◽  
Fixed Temperature ◽  
First Case ◽  
Ads Black Holes ◽  
Horizon Geometry ◽  
Black Hole Solutions

Abstract Motivated by the recent studies of the novel asymptotically global $$\hbox {AdS}_4$$AdS4 black hole with deformed horizon, we consider the action of Einstein–Maxwell gravity in AdS spacetime and construct the charged deforming AdS black holes with differential boundary. In contrast to deforming black hole without charge, there exists at least one value of horizon for an arbitrary temperature. The extremum of temperature is determined by charge q and divides the range of temperature into several parts. Moreover, we use an isometric embedding in the three-dimensional space to investigate the horizon geometry. The entropy and quasinormal modes of deforming charged AdS black hole are also studied in this paper. Due to the existence of charge q, the phase diagram of entropy is more complicated. We consider two cases of solutions: (1) fixing the chemical potential $$\mu $$μ; (2) changing the value of $$\mu $$μ according to the values of horizon radius and charge. In the first case, it is interesting to find there exist two families of black hole solutions with different horizon radii for a fixed temperature, but these two black holes have same horizon geometry and entropy. The second case ensures that deforming charged AdS black hole solutions can reduce to standard RN–AdS black holes.

scholarly journals Greybody factor and quasinormal modes of Regular Black Holes

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Ángel Rincón ◽  
Victor Santos
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Classical Solution ◽  
Quantum Number ◽  
Quasinormal Modes ◽  
Wkb Method ◽  
Regular Black Hole ◽  
Gravitational Perturbations ◽  
Black Hole Solutions

AbstractIn this work, we investigate the quasinormal frequencies of a class of regular black hole solutions which generalize Bardeen and Hayward spacetimes. In particular, we analyze scalar, vector and gravitational perturbations of the black hole with the semianalytic WKB method. We analyze in detail the behaviour of the spectrum depending on the parameter p/q of the black hole, the quantum number of angular momentum and the s number. In addition, we compare our results with the classical solution valid for $$p = q = 1$$ p = q = 1 .

scholarly journals Dirac quasinormal modes of power-Maxwell charged black holes in Rastall gravity

2020 ◽  
Vol 35 (23) ◽  
pp. 2050193
Author(s):  
Cai-Ying Shao ◽  
Yu Hu ◽  
Yu-Jie Tan ◽  
Cheng-Gang Shao ◽  
Kai Lin ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Matrix Method ◽  
Quasinormal Modes ◽  
Einstein Gravity ◽  
Late Time ◽  
Charged Black Holes ◽  
The Matrix ◽  
Black Hole Solutions ◽  
Extremal Black Holes

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 [Formula: see text], the spin–orbit quantum number. Also, the roles of the parameters [Formula: see text] and [Formula: see text], 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.

scholarly journals Scalar Perturbations of Black Holes in the f(R)=R−2αR Model

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 47
Author(s):  
Ping Li ◽  
Rui Jiang ◽  
Jian Lv ◽  
Xianghua Zhai
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Critical Frequency ◽  
Amplification Factor ◽  
Quasinormal Modes ◽  
Spherically Symmetric ◽  
Third Order ◽  
Charged Scalar ◽  
The Time Domain

In this paper, we study the perturbations of the charged static spherically symmetric black holes in the f(R)=R−2αR model by a scalar field. We analyze the quasinormal modes spectrum, superradiant modes, and superradiant instability of the black holes. The frequency of the quasinormal modes is calculated in the frequency domain by the third-order WKB method, and in the time domain by the finite difference method. The results by the two methods are consistent and show that the black hole stabilizes quicker for larger α satisfying the horizon condition. We then analyze the superradiant modes when the massive charged scalar field is scattered by the black hole. The frequency of the superradiant wave satisfies ω∈(μ2,ωc), where μ is the mass of the scalar field, and ωc is the critical frequency of the superradiance. The amplification factor is also calculated by numerical method. Furthermore, the superradiant instability of the black hole is studied analytically, and the results show that there is no superradiant instability for such a system.

scholarly journals Scalarized black holes

2021 ◽  
Author(s):  
Jose Luis Blázquez-Salcedo ◽  
Burkhard Kleihaus ◽  
Jutta Kunz
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Scalar Field ◽  
Alternative Theories Of Gravity ◽  
Gravitational Action ◽  
Theories Of Gravity ◽  
Bonnet Term ◽  
Alternative Theories ◽  
Black Hole Solutions

AbstractBlack holes represent outstanding astrophysical laboratories to test the strong gravity regime, since alternative theories of gravity may predict black hole solutions whose properties may differ distinctly from those of general relativity. When higher curvature terms are included in the gravitational action as, for instance, in the form of the Gauss–Bonnet term coupled to a scalar field, scalarized black holes result. Here we discuss several types of scalarized black holes and some of their properties.

scholarly journals Scalarized Einstein–Maxwell-scalar black holes in a cavity

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Feiyu Yao
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Black Hole ◽  
Scalar Field ◽  
Order Phase Transition ◽  
Phase Structure ◽  
Zeroth Order ◽  
Maxwell Fields ◽  
Domain Of Existence ◽  
Black Hole Solutions

AbstractIn this paper, we study the spontaneous scalarization of Reissner–Nordström (RN) black holes enclosed by a cavity in an Einstein–Maxwell-scalar (EMS) model with non-minimal couplings between the scalar and Maxwell fields. In this model, scalar-free RN black holes in a cavity may induce scalarized black holes due to the presence of a tachyonic instability of the scalar field near the event horizon. We calculate numerically the black hole solutions, and investigate the domain of existence, perturbative stability against spherical perturbations and phase structure. The scalarized solutions are always thermodynamically preferred over RN black holes in a cavity. In addition, a reentrant phase transition, composed of a zeroth-order phase transition and a second-order one, occurs for large enough electric charge Q.

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