scholarly journals Massless scalar fields and topological black holes

2000 ◽  
Vol 61 (8) ◽  
Author(s):  
Tekin Dereli ◽  
Yuri N. Obukhov
Keyword(s):  
Black Holes ◽  
Scalar Fields ◽  
Massless Scalar

Stationary bound states of massless scalar fields around black holes and black hole analogues

2015 ◽  
Vol 24 (09) ◽  
pp. 1542018 ◽  
Author(s):  
Carolina L. Benone ◽  
Luís C. B. Crispino ◽  
Carlos A. R. Herdeiro ◽  
Eugen Radu
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Spatial Distribution ◽  
Scalar Field ◽  
Bound States ◽  
Neumann Boundary ◽  
Mass Term ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Field System

We discuss stationary bound states, a.k.a. clouds, for a massless test scalar field around Kerr black holes (BHs) and spinning acoustic BH analogues. In view of the absence of a mass term, the trapping is achieved via enclosing the BH — scalar field system in a cavity and imposing Dirichlet or Neumann boundary conditions. We discuss the variation of these bounds states with the discrete parameters that label them, as well as their spatial distribution, complementing results in our previous work [C. L. Benone, L. C. B. Crispino, C. Herdeiro and E. Radu, Phys. Rev. D91 (2015) 104038].

Absorption of zero-mass planar waves by dirty black holes

2018 ◽  
Vol 27 (11) ◽  
pp. 1843017 ◽  
Author(s):  
Caio F. B. Macedo ◽  
Luiz C. S. Leite ◽  
Luís C. B. Crispino
Keyword(s):  
Black Holes ◽  
Cross Section ◽  
Accretion Disks ◽  
Absorption Cross Section ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Absorption Cross ◽  
Thin Spherical Shell ◽  
Nonlinear Nature ◽  
Selection Of

Astrophysical black holes are often with companions, including other gravitating objects, accretion disks, electromagnetic fields, and others. Because of the nonlinear nature of general relativity, it is difficult to account for the gravitational effects of these companions, which can only be investigated analytically for very few cases. In this paper, we consider black holes with surrounding matter — often called dirty black holes — and analyze the absorption cross section of massless scalar fields. We start by laying out the generic setup for spherically symmetric scenarios and then specify for a simple model. We consider planar massless scalar waves impinging upon a Schwarzschild black hole surrounded by a thin spherical shell, and compute the absorption cross section. We present a selection of numerical results complementary to those presented in [C. F. B. Macedo, L. C. S. Leite and L. C. B. Crispino, Phys. Rev. D 93 (2016) 024027, arXiv:1511.08781 [gr-qc]] for arbitrary frequencies, considering different values of the shell position as well as its mass.

scholarly journals Scalar waves in regular Bardeen black holes: Scattering, absorption and quasinormal modes

2016 ◽  
Vol 25 (09) ◽  
pp. 1641008 ◽  
Author(s):  
Caio F. B. Macedo ◽  
Luís C. B. Crispino ◽  
Ednilton S. de Oliveira
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Quasinormal Modes ◽  
Scalar Fields ◽  
Scattering Cross Section ◽  
Massless Scalar ◽  
Absorption Cross ◽  
Scattering Cross

We discuss the phenomenology of massless scalar fields around a regular Bardeen black hole, namely absorption cross-section, scattering cross-section and quasinormal modes. We compare the Bardeen and Reissner–Nordström black holes, showing limiting cases for which their properties are similar.

scholarly journals Analytic treatment of near-extremal charged black holes supporting non-minimally coupled massless scalar clouds

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Shahar Hod
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Coupling Parameter ◽  
Analytical Formula ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Charged Black Holes ◽  
Black Hole Spacetimes ◽  
Electromagnetic Tensor

AbstractIt has recently been revealed that massless scalar fields which are non-minimally coupled to the Maxwell electromagnetic tensor can be supported in the exterior spacetime regions of spherically symmetric charged black holes. The boundary between scalarized charged black-hole spacetimes and bald (scalarless) Reissner–Nordström black holes is determined by the presence of a critical existence-line which describes spatially regular linearized scalar ‘clouds’ that are supported in the black-hole spacetime. In the present paper we use analytical techniques in order to solve the Klein–Gordon wave equation for the non-minimally coupled linearized scalar fields in the spacetimes of near-extremal supporting black holes. In particular, we derive a remarkably compact analytical formula for the discrete resonant spectrum $$\{\alpha (l,Q/M;n)\}^{n=\infty }_{n=1}$$ { α ( l , Q / M ; n ) } n = 1 n = ∞ which characterizes the dimensionless coupling parameter of the composed Reissner–Nordström-black-hole-nonminimally-coupled-massless-scalar-field configurations along the critical existence-line of the Einstein–Maxwell-scalar theory (here Q/M is the dimensionless charge-to-mass ratio of the central supporting black hole and l is the angular harmonic index of the supported scalar configurations).

scholarly journals Black holes with regular horizons in Maxwell-scalar gravity

1996 ◽  
Vol 74 (1-2) ◽  
pp. 17-28 ◽  
Author(s):  
Slava G. Turyshev
Keyword(s):  
Black Holes ◽  
Scalar Field ◽  
Scalar Curvature ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Massless Scalar Field ◽  
Coupling Constant ◽  
Minkowski Space Time ◽  
Special Cases ◽  
Nontrivial Coupling

A class of exact static spherically symmetric solutions of the Einstein–Maxwell gravity coupled to a massless scalar field is obtained in the harmonic coordinates of Minkowski space-time. For each value of the coupling constant a, these solutions are characterized by a set of three parameters, the physical mass μ0, the electric charge Q0 and the scalar-field parameter k. We find that the solutions for both gravitational and electromagnetic fields are not only affected by the scalar field, but also the nontrivial coupling with matter constrains the scalar field itself. In particular, we find that the constant k differs generically from ±1/2, falling into the interval [Formula: see text]. It takes these values only for black holes or in the case when a scalar field [Formula: see text] is totally decoupled from the matter. Our results differ from those previously obtained in that the presence of an arbitrary coupling constant a gives an opportunity to rule out the nonphysical horizons. In one of the special cases, the obtained solution corresponds to a charged dilatonic black hole with only one horizon μ+ and hence to the Kaluza–Klein case. The most remarkable property of this result is that the metric, the scalar curvature, and both the electromagnetic and scalar fields are all regular on this surface. Moreover, while studying the dilaton charge, we found that the inclusion of the scalar field in the theory resulted in a contraction of the horizon. The behavior of the scalar curvature was analysed.

scholarly journals The Connection Between Entropy and the Absorption Spectra of Schwarzschild Black Holes for Light and Massless Scalar Fields

Entropy ◽  
2009 ◽  
Vol 11 (1) ◽  
pp. 17-31 ◽  
Author(s):  
Sergio Mendoza ◽  
Xavier Hernandez ◽  
Pablo Rendón ◽  
C. Lopez-Monsalvo ◽  
Roberto Velasco-Segura
Keyword(s):  
Black Holes ◽  
Absorption Spectra ◽  
Scalar Fields ◽  
Massless Scalar

Dynamics of scalar shell for rotating and charged rotating BTZ black holes

2019 ◽  
Vol 35 (02) ◽  
pp. 1950350 ◽  
Author(s):  
M. Sharif ◽  
Faisal Javed
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Thin Shell ◽  
Equations Of Motion ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Massive Scalar ◽  
Matter Distribution ◽  
Dynamical Equations

This paper studies the dynamics of thin-shell for (2 + 1)-dimensional rotating and charged rotating Bañados–Teitelboim–Zanelli black holes by using Israel thin-shell formalism. We consider the matter distribution located at thin-shell associated with a scalar field and analyze its effects on the dynamics of thin-shell through equations of motion and effective potential. The corresponding dynamical equations are numerically studied for both massless as well as massive scalar fields. For rotating case, the rate of expansion and collapse increases with massless scalar shell but decreases for massive case. For charged rotating, the rate of expansion and collapse decreases by increasing angular momentum for both massless as well as massive case. We conclude that the rate of expansion and collapse of the rotating case is greater than charged rotating black hole.

scholarly journals Quasinormal modes and absorption cross-sections of Born–Infeld–de Sitter black holes

2017 ◽  
Vol 26 (10) ◽  
pp. 1750112 ◽  
Author(s):  
Nora Bretón ◽  
Tyler Clark ◽  
Sharmanthie Fernando
Keyword(s):  
Black Holes ◽  
Cross Sections ◽  
Quasinormal Modes ◽  
Eikonal Approximation ◽  
Scalar Fields ◽  
Massless Scalar ◽  
Absorption Cross ◽  
De Sitter ◽  
Sinc Approximation ◽  
Null Geodesics

In this paper, we have studied QNM modes and absorption cross-sections of Born–Infeld–de Sitter black holes. WKB approximation is employed to compute the QNM modes of massless scalar fields. We have also used null geodesics to compute quasinormal modes in the eikonal approximation. In the eikonal limit, QNMs of black holes are determined by the parameters of the circular null geodesics. Unstable circular null orbits are derived from the effective metric which is obeyed by light rays under the influence of a nonlinear electromagnetic field. Comparison is shown with the QNM of the linear electromagnetic counterpart, the Reissner–Nordström black hole. Furthermore, the null geodesics are employed to compute the absorption cross-sections in the high frequency limit via the sinc approximation.

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