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Register a new userDynamical charged black hole spontaneous scalarization in Anti-de Sitter spacetimes
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We study the fully nonlinear dynamics of black hole spontaneous scalarizations in Einstein-Maxwell scalar theory with coupling function $f(phi)=e^{-bphi^{2}}$, which can transform usual Reissner-Nordstrom Anti-de Sitter (RN-AdS) black holes into hairy black holes. Fixing the Arnowitt-Deser-Misner mass of the system, the initial scalar perturbation will destroy the original RN-AdS black hole and turn it into a hairy black hole provided that the constant $-b$ in the coupling function and the charge of the original black hole are sufficiently large, while the cosmological constant is small enough. In the scalarization process, we observe that the black hole irreducible mass initially increases exponentially, then it approaches to and finally saturates at a finite value. Choosing stronger coupling and larger black hole charge, we find that the black hole mass exponentially grows earlier and it takes a longer time for a hairy black hole to be developed and stabilized. We further examine phase structure properties in the scalarization process and confirm the observations in the non-linear dynamical study.
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In this paper, static electrically charged black hole solutions with cosmological constant are investigated in an Einstein-Hilbert theory of gravity with additional quadratic curvature terms. Beside the analytic Schwarzschild (Anti-) de Sitter solutions, non-Schwarzschild (Anti-) de Sitter solutions are also obtained numerically by employing the shooting method. The results show that there exist two groups of asymptotically (Anti-) de Sitter spacetimes for both charged and uncharged black holes. In particular, it was found that for uncharged black holes the first group can be reduced to the Schwarzschild (Anti-) de Sitter solution, while the second group is intrinsically different from a Schwarzschild (Anti-) de Sitter solution even when the charge and the cosmological constant become zero.
We obtain the Kerr-anti-de-sitter (Kerr-AdS) and Kerr-de-sitter (Kerr-dS) black hole (BH) solutions to the Einstein field equation in the perfect fluid dark matter background using the Newman-Janis method and Mathematica package. We discuss in detail the black hole properties and obtain the following main results: (i) From the horizon equation $g_{rr}=0$, we derive the relation between the perfect fluid dark matter parameter $alpha$ and the cosmological constant $Lambda$ when the cosmological horizon $r_{Lambda}$ exists. For $Lambda=0$, we find that $alpha$ is in the range $0<alpha<2M$ for $alpha>0$ and $-7.18M<alpha<0$ for $alpha<0$. For positive cosmological constant $Lambda$ (Kerr-AdS BH), $alpha_{max}$ decreases if $alpha>0$, and $alpha_{min}$ increases if $alpha<0$. For negative cosmological constant $-Lambda$ (Kerr-dS BH), $alpha_{max}$ increases if $alpha>0$ and $alpha_{min}$ decreases if $alpha<0$; (ii) An ergosphere exists between the event horizon and the outer static limit surface. The size of the ergosphere evolves oppositely for $alpha>0$ and $alpha<0$, while decreasing with the increasing $midalphamid$. When there is sufficient dark matter around the black hole, the black hole spacetime changes remarkably; (iii) The singularity of these black holes is the same as that of rotational black holes. In addition, we study the geodesic motion using the Hamilton-Jacobi formalism and find that when $alpha$ is in the above ranges for $Lambda=0$, stable orbits exist. Furthermore, the rotational velocity of the black hole in the equatorial plane has different behaviour for different $alpha$ and the black hole spin $a$. It is asymptotically flat and independent of $alpha$ if $alpha>0$ while is asymptotically flat only when $alpha$ is close to zero if $alpha<0$.
We study the spontaneous scalarization of spherically symmetric, static and asymptotically Anti-de Sitter (aAdS) black holes in a scalar-tensor gravity model with non-mininal coupling of the form $phi^2left(alpha{cal R} + gamma {cal G}right)$, where $alpha$ and $gamma$ are constants, while ${cal R}$ and ${cal G}$ are the Ricci scalar and Gauss-Bonnet term, respectively. Since these terms act as an effective ``mass for the scalar field, non-trivial values of the scalar field in the black hole space-time are possible for {it a priori} vanishing scalar field mass. In particular, we demonstrate that the scalarization of an aAdS black hole requires the curvature invariant $-left(alpha{cal R} + gamma {cal G}right)$ to drop below the Breitenlohner-Freedman bound close to the black hole horizon, while it asymptotes to a value well above the bound. The dimension of the dual operator on the AdS boundary depends on the parameters $alpha$ and $gamma$ and we demonstrate that -- for fixed operator dimension -- the expectation value of this dual operator increases with decreasing temperature of the black hole, i.e. of the dual field theory. When taking backreaction of the space-time into account, we find that the scalarization of the black hole is the dual description of a phase transition in a strongly coupled quantum system, i.e. corresponds to a holographic phase transition. A possible application are liquid-gas quantum phase transitions, e.g. in $^4$He. Finally, we demonstrate that extremal black holes with $AdS_2times S^2$ near-horizon geometry {it cannot support regular scalar fields on the horizon} in the scalar-tensor model studied here.
We study the linear instability of the charged massless scalar perturbation in regularized 4D charged Einstein-Gauss-Bonnet-AdS black holes by exploring the quasinormal modes. We find that the linear instability is triggered by superradiance. The charged massless scalar perturbation becomes more unstable when increasing the Gauss-Bonnet coupling constant or the black hole charge. Meanwhile, decreasing} the AdS radius will make the charged massless scalar perturbation} more stable. The stable region in parameter space $(alpha,Q,Lambda)$ is given. Moreover, we find that the charged massless scalar perturbation is more unstable for larger scalar charge. The modes of multipoles are more stable than that of the monopole.
We analytically and numerically study quasinormal frequencies (QNFs) of neutral and charged scalar fields in the charged anti-de Sitter (AdS) black holes and discuss the stability of the black holes in terms of the QNFs. We focus on the range of the mass squared $mu^2$ of the scalar fields for which the Robin boundary condition parametrised by $zeta$ applies at the conformal infinity. We find that if the black hole of radius $r_{+}$ and charge $Q$ is much smaller than the AdS length $ell$, the instability of the charged scalar field can be understood in terms of superradiance in the reflective boundary condition. Noting that the s-wave normal frequency in the AdS spacetime is a decreasing function of $zeta$, we find that if $|eQ|ell/r_{+}$ is greater than $(3+sqrt{9+4mu^2ell^2})/2$, where $e$ is the charge of the scalar field, the black hole is superradiantly unstable irrespectively of $zeta$. On the other hand, if $|eQ|ell/r_{+}$ is equal to or smaller than this critical value, the stability crucially depends on $zeta$ and there appears a purely oscillating mode at the onset of the instability. We argue that as a result of the superradiant instability, the scalar field gains charge from the black hole and energy from its ambient electric field, while the black hole gives charge to the scalar field and gains energy from the scalar field but decreases its asymptotic mass parameter.
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